Alien-FreeImage
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src/Source/LibPNG/pngread.c view on Meta::CPAN
#ifdef PNG_READ_tEXt_SUPPORTED
else if (chunk_name == png_tEXt)
png_handle_tEXt(png_ptr, info_ptr, length);
#endif
#ifdef PNG_READ_tIME_SUPPORTED
else if (chunk_name == png_tIME)
png_handle_tIME(png_ptr, info_ptr, length);
#endif
#ifdef PNG_READ_tRNS_SUPPORTED
else if (chunk_name == png_tRNS)
png_handle_tRNS(png_ptr, info_ptr, length);
#endif
#ifdef PNG_READ_zTXt_SUPPORTED
else if (chunk_name == png_zTXt)
png_handle_zTXt(png_ptr, info_ptr, length);
#endif
#ifdef PNG_READ_iTXt_SUPPORTED
else if (chunk_name == png_iTXt)
png_handle_iTXt(png_ptr, info_ptr, length);
#endif
else
png_handle_unknown(png_ptr, info_ptr, length,
PNG_HANDLE_CHUNK_AS_DEFAULT);
}
}
#endif /* SEQUENTIAL_READ */
/* Optional call to update the users info_ptr structure */
void PNGAPI
png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
{
png_debug(1, "in png_read_update_info");
if (png_ptr != NULL)
{
if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
{
png_read_start_row(png_ptr);
# ifdef PNG_READ_TRANSFORMS_SUPPORTED
png_read_transform_info(png_ptr, info_ptr);
# else
PNG_UNUSED(info_ptr)
# endif
}
/* New in 1.6.0 this avoids the bug of doing the initializations twice */
else
png_app_error(png_ptr,
"png_read_update_info/png_start_read_image: duplicate call");
}
}
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Initialize palette, background, etc, after transformations
* are set, but before any reading takes place. This allows
* the user to obtain a gamma-corrected palette, for example.
* If the user doesn't call this, we will do it ourselves.
*/
void PNGAPI
png_start_read_image(png_structrp png_ptr)
{
png_debug(1, "in png_start_read_image");
if (png_ptr != NULL)
{
if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
png_read_start_row(png_ptr);
/* New in 1.6.0 this avoids the bug of doing the initializations twice */
else
png_app_error(png_ptr,
"png_start_read_image/png_read_update_info: duplicate call");
}
}
#endif /* SEQUENTIAL_READ */
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Undoes intrapixel differencing,
* NOTE: this is apparently only supported in the 'sequential' reader.
*/
static void
png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_read_intrapixel");
if (
(row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
{
int bytes_per_pixel;
png_uint_32 row_width = row_info->width;
if (row_info->bit_depth == 8)
{
png_bytep rp;
png_uint_32 i;
if (row_info->color_type == PNG_COLOR_TYPE_RGB)
bytes_per_pixel = 3;
else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
bytes_per_pixel = 4;
else
return;
for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
{
*(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
*(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
}
}
else if (row_info->bit_depth == 16)
{
src/Source/LibPNG/pngread.c view on Meta::CPAN
}
void PNGAPI
png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
{
if (png_ptr == NULL)
return;
png_ptr->read_row_fn = read_row_fn;
}
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
#ifdef PNG_INFO_IMAGE_SUPPORTED
void PNGAPI
png_read_png(png_structrp png_ptr, png_inforp info_ptr,
int transforms,
voidp params)
{
if (png_ptr == NULL || info_ptr == NULL)
return;
/* png_read_info() gives us all of the information from the
* PNG file before the first IDAT (image data chunk).
*/
png_read_info(png_ptr, info_ptr);
if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
png_error(png_ptr, "Image is too high to process with png_read_png()");
/* -------------- image transformations start here ------------------- */
/* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
* is not implemented. This will only happen in de-configured (non-default)
* libpng builds. The results can be unexpected - png_read_png may return
* short or mal-formed rows because the transform is skipped.
*/
/* Tell libpng to strip 16-bit/color files down to 8 bits per color.
*/
if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
/* Added at libpng-1.5.4. "strip_16" produces the same result that it
* did in earlier versions, while "scale_16" is now more accurate.
*/
#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
png_set_scale_16(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
#endif
/* If both SCALE and STRIP are required pngrtran will effectively cancel the
* latter by doing SCALE first. This is ok and allows apps not to check for
* which is supported to get the right answer.
*/
if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
png_set_strip_16(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
#endif
/* Strip alpha bytes from the input data without combining with
* the background (not recommended).
*/
if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
png_set_strip_alpha(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
#endif
/* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
* byte into separate bytes (useful for paletted and grayscale images).
*/
if ((transforms & PNG_TRANSFORM_PACKING) != 0)
#ifdef PNG_READ_PACK_SUPPORTED
png_set_packing(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
#endif
/* Change the order of packed pixels to least significant bit first
* (not useful if you are using png_set_packing).
*/
if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
#ifdef PNG_READ_PACKSWAP_SUPPORTED
png_set_packswap(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
#endif
/* Expand paletted colors into true RGB triplets
* Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
* Expand paletted or RGB images with transparency to full alpha
* channels so the data will be available as RGBA quartets.
*/
if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
#ifdef PNG_READ_EXPAND_SUPPORTED
png_set_expand(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
#endif
/* We don't handle background color or gamma transformation or quantizing.
*/
/* Invert monochrome files to have 0 as white and 1 as black
*/
if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
#ifdef PNG_READ_INVERT_SUPPORTED
png_set_invert_mono(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
#endif
/* If you want to shift the pixel values from the range [0,255] or
* [0,65535] to the original [0,7] or [0,31], or whatever range the
* colors were originally in:
*/
if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
#ifdef PNG_READ_SHIFT_SUPPORTED
if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
png_set_shift(png_ptr, &info_ptr->sig_bit);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
#endif
/* Flip the RGB pixels to BGR (or RGBA to BGRA) */
if ((transforms & PNG_TRANSFORM_BGR) != 0)
#ifdef PNG_READ_BGR_SUPPORTED
png_set_bgr(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
#endif
/* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
png_set_swap_alpha(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
#endif
/* Swap bytes of 16-bit files to least significant byte first */
if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
#ifdef PNG_READ_SWAP_SUPPORTED
png_set_swap(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
#endif
/* Added at libpng-1.2.41 */
/* Invert the alpha channel from opacity to transparency */
if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
png_set_invert_alpha(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
#endif
/* Added at libpng-1.2.41 */
/* Expand grayscale image to RGB */
if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
png_set_gray_to_rgb(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
#endif
/* Added at libpng-1.5.4 */
if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
#ifdef PNG_READ_EXPAND_16_SUPPORTED
png_set_expand_16(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
#endif
/* We don't handle adding filler bytes */
/* We use png_read_image and rely on that for interlace handling, but we also
* call png_read_update_info therefore must turn on interlace handling now:
*/
(void)png_set_interlace_handling(png_ptr);
/* Optional call to gamma correct and add the background to the palette
* and update info structure. REQUIRED if you are expecting libpng to
* update the palette for you (i.e., you selected such a transform above).
*/
png_read_update_info(png_ptr, info_ptr);
/* -------------- image transformations end here ------------------- */
png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
if (info_ptr->row_pointers == NULL)
{
png_uint_32 iptr;
info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
info_ptr->height * (sizeof (png_bytep))));
for (iptr=0; iptr<info_ptr->height; iptr++)
info_ptr->row_pointers[iptr] = NULL;
info_ptr->free_me |= PNG_FREE_ROWS;
for (iptr = 0; iptr < info_ptr->height; iptr++)
info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
png_malloc(png_ptr, info_ptr->rowbytes));
}
png_read_image(png_ptr, info_ptr->row_pointers);
info_ptr->valid |= PNG_INFO_IDAT;
/* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
png_read_end(png_ptr, info_ptr);
PNG_UNUSED(params)
}
#endif /* INFO_IMAGE */
#endif /* SEQUENTIAL_READ */
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
/* SIMPLIFIED READ
*
* This code currently relies on the sequential reader, though it could easily
* be made to work with the progressive one.
*/
/* Arguments to png_image_finish_read: */
/* Encoding of PNG data (used by the color-map code) */
# define P_NOTSET 0 /* File encoding not yet known */
# define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
# define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
# define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
# define P_LINEAR8 4 /* 8-bit linear: only from a file value */
/* Color-map processing: after libpng has run on the PNG image further
* processing may be needed to convert the data to color-map indices.
*/
#define PNG_CMAP_NONE 0
#define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
#define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
#define PNG_CMAP_RGB 3 /* Process RGB data */
#define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
/* The following document where the background is for each processing case. */
#define PNG_CMAP_NONE_BACKGROUND 256
#define PNG_CMAP_GA_BACKGROUND 231
#define PNG_CMAP_TRANS_BACKGROUND 254
#define PNG_CMAP_RGB_BACKGROUND 256
#define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
typedef struct
{
/* Arguments: */
png_imagep image;
png_voidp buffer;
png_int_32 row_stride;
png_voidp colormap;
png_const_colorp background;
/* Local variables: */
png_voidp local_row;
png_voidp first_row;
ptrdiff_t row_bytes; /* step between rows */
int file_encoding; /* E_ values above */
png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
int colormap_processing; /* PNG_CMAP_ values above */
} png_image_read_control;
/* Do all the *safe* initialization - 'safe' means that png_error won't be
* called, so setting up the jmp_buf is not required. This means that anything
* called from here must *not* call png_malloc - it has to call png_malloc_warn
* instead so that control is returned safely back to this routine.
*/
static int
png_image_read_init(png_imagep image)
{
if (image->opaque == NULL)
{
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
png_safe_error, png_safe_warning);
/* And set the rest of the structure to NULL to ensure that the various
* fields are consistent.
*/
memset(image, 0, (sizeof *image));
image->version = PNG_IMAGE_VERSION;
if (png_ptr != NULL)
{
png_infop info_ptr = png_create_info_struct(png_ptr);
if (info_ptr != NULL)
{
png_controlp control = png_voidcast(png_controlp,
png_malloc_warn(png_ptr, (sizeof *control)));
if (control != NULL)
{
memset(control, 0, (sizeof *control));
control->png_ptr = png_ptr;
control->info_ptr = info_ptr;
control->for_write = 0;
image->opaque = control;
return 1;
}
/* Error clean up */
png_destroy_info_struct(png_ptr, &info_ptr);
}
png_destroy_read_struct(&png_ptr, NULL, NULL);
}
return png_image_error(image, "png_image_read: out of memory");
}
return png_image_error(image, "png_image_read: opaque pointer not NULL");
src/Source/LibPNG/pngread.c view on Meta::CPAN
set_file_encoding(png_image_read_control *display)
{
png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
if (png_gamma_significant(g) != 0)
{
if (png_gamma_not_sRGB(g) != 0)
{
display->file_encoding = P_FILE;
display->gamma_to_linear = png_reciprocal(g);
}
else
display->file_encoding = P_sRGB;
}
else
display->file_encoding = P_LINEAR8;
}
static unsigned int
decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
{
if (encoding == P_FILE) /* double check */
encoding = display->file_encoding;
if (encoding == P_NOTSET) /* must be the file encoding */
{
set_file_encoding(display);
encoding = display->file_encoding;
}
switch (encoding)
{
case P_FILE:
value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
break;
case P_sRGB:
value = png_sRGB_table[value];
break;
case P_LINEAR:
break;
case P_LINEAR8:
value *= 257;
break;
default:
png_error(display->image->opaque->png_ptr,
"unexpected encoding (internal error)");
break;
}
return value;
}
static png_uint_32
png_colormap_compose(png_image_read_control *display,
png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
png_uint_32 background, int encoding)
{
/* The file value is composed on the background, the background has the given
* encoding and so does the result, the file is encoded with P_FILE and the
* file and alpha are 8-bit values. The (output) encoding will always be
* P_LINEAR or P_sRGB.
*/
png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
png_uint_32 b = decode_gamma(display, background, encoding);
/* The alpha is always an 8-bit value (it comes from the palette), the value
* scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
*/
f = f * alpha + b * (255-alpha);
if (encoding == P_LINEAR)
{
/* Scale to 65535; divide by 255, approximately (in fact this is extremely
* accurate, it divides by 255.00000005937181414556, with no overflow.)
*/
f *= 257; /* Now scaled by 65535 */
f += f >> 16;
f = (f+32768) >> 16;
}
else /* P_sRGB */
f = PNG_sRGB_FROM_LINEAR(f);
return f;
}
/* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
* be 8-bit.
*/
static void
png_create_colormap_entry(png_image_read_control *display,
png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
png_uint_32 alpha, int encoding)
{
png_imagep image = display->image;
const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB;
const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
(red != green || green != blue);
if (ip > 255)
png_error(image->opaque->png_ptr, "color-map index out of range");
/* Update the cache with whether the file gamma is significantly different
* from sRGB.
*/
if (encoding == P_FILE)
{
if (display->file_encoding == P_NOTSET)
set_file_encoding(display);
/* Note that the cached value may be P_FILE too, but if it is then the
* gamma_to_linear member has been set.
*/
encoding = display->file_encoding;
}
if (encoding == P_FILE)
{
png_fixed_point g = display->gamma_to_linear;
red = png_gamma_16bit_correct(red*257, g);
green = png_gamma_16bit_correct(green*257, g);
blue = png_gamma_16bit_correct(blue*257, g);
src/Source/LibPNG/pngread.c view on Meta::CPAN
for (a=1; a<5; ++a)
{
unsigned int g;
for (g=0; g<6; ++g)
png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
P_sRGB);
}
return i;
}
#define PNG_GA_COLORMAP_ENTRIES 256
static int
make_rgb_colormap(png_image_read_control *display)
{
unsigned int i, r;
/* Build a 6x6x6 opaque RGB cube */
for (i=r=0; r<6; ++r)
{
unsigned int g;
for (g=0; g<6; ++g)
{
unsigned int b;
for (b=0; b<6; ++b)
png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
P_sRGB);
}
}
return i;
}
#define PNG_RGB_COLORMAP_ENTRIES 216
/* Return a palette index to the above palette given three 8-bit sRGB values. */
#define PNG_RGB_INDEX(r,g,b) \
((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
static int
png_image_read_colormap(png_voidp argument)
{
png_image_read_control *display =
png_voidcast(png_image_read_control*, argument);
const png_imagep image = display->image;
const png_structrp png_ptr = image->opaque->png_ptr;
const png_uint_32 output_format = image->format;
const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB;
unsigned int cmap_entries;
unsigned int output_processing; /* Output processing option */
unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
/* Background information; the background color and the index of this color
* in the color-map if it exists (else 256).
*/
unsigned int background_index = 256;
png_uint_32 back_r, back_g, back_b;
/* Flags to accumulate things that need to be done to the input. */
int expand_tRNS = 0;
/* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
* very difficult to do, the results look awful, and it is difficult to see
* what possible use it is because the application can't control the
* color-map.
*/
if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
png_ptr->num_trans > 0) /* alpha in input */ &&
((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
{
if (output_encoding == P_LINEAR) /* compose on black */
back_b = back_g = back_r = 0;
else if (display->background == NULL /* no way to remove it */)
png_error(png_ptr,
"a background color must be supplied to remove alpha/transparency");
/* Get a copy of the background color (this avoids repeating the checks
* below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
* output format.
*/
else
{
back_g = display->background->green;
if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
{
back_r = display->background->red;
back_b = display->background->blue;
}
else
back_b = back_r = back_g;
}
}
else if (output_encoding == P_LINEAR)
back_b = back_r = back_g = 65535;
else
back_b = back_r = back_g = 255;
/* Default the input file gamma if required - this is necessary because
* libpng assumes that if no gamma information is present the data is in the
* output format, but the simplified API deduces the gamma from the input
* format.
*/
if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
{
/* Do this directly, not using the png_colorspace functions, to ensure
* that it happens even if the colorspace is invalid (though probably if
* it is the setting will be ignored) Note that the same thing can be
* achieved at the application interface with png_set_gAMA.
*/
if (png_ptr->bit_depth == 16 &&
(image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
else
png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
}
/* Decide what to do based on the PNG color type of the input data. The
* utility function png_create_colormap_entry deals with most aspects of the
* output transformations; this code works out how to produce bytes of
* color-map entries from the original format.
*/
switch (png_ptr->color_type)
{
case PNG_COLOR_TYPE_GRAY:
if (png_ptr->bit_depth <= 8)
{
/* There at most 256 colors in the output, regardless of
* transparency.
*/
unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
cmap_entries = 1U << png_ptr->bit_depth;
if (cmap_entries > image->colormap_entries)
png_error(png_ptr, "gray[8] color-map: too few entries");
step = 255 / (cmap_entries - 1);
output_processing = PNG_CMAP_NONE;
/* If there is a tRNS chunk then this either selects a transparent
* value or, if the output has no alpha, the background color.
*/
if (png_ptr->num_trans > 0)
{
trans = png_ptr->trans_color.gray;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
}
/* png_create_colormap_entry just takes an RGBA and writes the
* corresponding color-map entry using the format from 'image',
* including the required conversion to sRGB or linear as
* appropriate. The input values are always either sRGB (if the
* gamma correction flag is 0) or 0..255 scaled file encoded values
* (if the function must gamma correct them).
*/
for (i=val=0; i<cmap_entries; ++i, val += step)
{
/* 'i' is a file value. While this will result in duplicated
* entries for 8-bit non-sRGB encoded files it is necessary to
* have non-gamma corrected values to do tRNS handling.
*/
if (i != trans)
png_create_colormap_entry(display, i, val, val, val, 255,
P_FILE/*8-bit with file gamma*/);
/* Else this entry is transparent. The colors don't matter if
* there is an alpha channel (back_alpha == 0), but it does no
* harm to pass them in; the values are not set above so this
* passes in white.
*
* NOTE: this preserves the full precision of the application
* supplied background color when it is used.
*/
else
png_create_colormap_entry(display, i, back_r, back_g, back_b,
back_alpha, output_encoding);
}
/* We need libpng to preserve the original encoding. */
data_encoding = P_FILE;
/* The rows from libpng, while technically gray values, are now also
* color-map indices; however, they may need to be expanded to 1
* byte per pixel. This is what png_set_packing does (i.e., it
* unpacks the bit values into bytes.)
*/
if (png_ptr->bit_depth < 8)
png_set_packing(png_ptr);
}
else /* bit depth is 16 */
{
/* The 16-bit input values can be converted directly to 8-bit gamma
* encoded values; however, if a tRNS chunk is present 257 color-map
* entries are required. This means that the extra entry requires
* special processing; add an alpha channel, sacrifice gray level
* 254 and convert transparent (alpha==0) entries to that.
*
* Use libpng to chop the data to 8 bits. Convert it to sRGB at the
* same time to minimize quality loss. If a tRNS chunk is present
* this means libpng must handle it too; otherwise it is impossible
* to do the exact match on the 16-bit value.
*
* If the output has no alpha channel *and* the background color is
* gray then it is possible to let libpng handle the substitution by
* ensuring that the corresponding gray level matches the background
* color exactly.
*/
data_encoding = P_sRGB;
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray[16] color-map: too few entries");
cmap_entries = make_gray_colormap(display);
if (png_ptr->num_trans > 0)
{
unsigned int back_alpha;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
back_alpha = 0;
else
{
if (back_r == back_g && back_g == back_b)
{
/* Background is gray; no special processing will be
* required.
*/
png_color_16 c;
png_uint_32 gray = back_g;
if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(gray * 255);
/* And make sure the corresponding palette entry
* matches.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 65535, P_LINEAR);
}
/* The background passed to libpng, however, must be the
* sRGB value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
/* NOTE: does this work without expanding tRNS to alpha?
* It should be the color->gray case below apparently
* doesn't.
*/
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_NONE;
break;
}
back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
}
/* output_processing means that the libpng-processed row will be
* 8-bit GA and it has to be processing to single byte color-map
* values. Entry 254 is replaced by either a completely
* transparent entry or by the background color at full
* precision (and the background color is not a simple gray
* level in this case.)
*/
expand_tRNS = 1;
output_processing = PNG_CMAP_TRANS;
background_index = 254;
/* And set (overwrite) color-map entry 254 to the actual
* background color at full precision.
*/
png_create_colormap_entry(display, 254, back_r, back_g, back_b,
back_alpha, output_encoding);
}
else
output_processing = PNG_CMAP_NONE;
}
break;
case PNG_COLOR_TYPE_GRAY_ALPHA:
/* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
* of 65536 combinations. If, however, the alpha channel is to be
* removed there are only 256 possibilities if the background is gray.
* (Otherwise there is a subset of the 65536 possibilities defined by
* the triangle between black, white and the background color.)
*
* Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
* worry about tRNS matching - tRNS is ignored if there is an alpha
* channel.
*/
data_encoding = P_sRGB;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray+alpha color-map: too few entries");
cmap_entries = make_ga_colormap(display);
background_index = PNG_CMAP_GA_BACKGROUND;
output_processing = PNG_CMAP_GA;
}
else /* alpha is removed */
{
/* Alpha must be removed as the PNG data is processed when the
* background is a color because the G and A channels are
* independent and the vector addition (non-parallel vectors) is a
* 2-D problem.
*
* This can be reduced to the same algorithm as above by making a
* colormap containing gray levels (for the opaque grays), a
* background entry (for a transparent pixel) and a set of four six
* level color values, one set for each intermediate alpha value.
* See the comments in make_ga_colormap for how this works in the
* per-pixel processing.
*
* If the background is gray, however, we only need a 256 entry gray
* level color map. It is sufficient to make the entry generated
* for the background color be exactly the color specified.
*/
if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
(back_r == back_g && back_g == back_b))
{
/* Background is gray; no special processing will be required. */
png_color_16 c;
png_uint_32 gray = back_g;
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray-alpha color-map: too few entries");
cmap_entries = make_gray_colormap(display);
if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(gray * 255);
/* And make sure the corresponding palette entry matches. */
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 65535, P_LINEAR);
}
/* The background passed to libpng, however, must be the sRGB
* value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_NONE;
}
else
{
png_uint_32 i, a;
/* This is the same as png_make_ga_colormap, above, except that
* the entries are all opaque.
*/
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "ga-alpha color-map: too few entries");
i = 0;
while (i < 231)
{
png_uint_32 gray = (i * 256 + 115) / 231;
png_create_colormap_entry(display, i++, gray, gray, gray,
255, P_sRGB);
}
/* NOTE: this preserves the full precision of the application
* background color.
*/
background_index = i;
png_create_colormap_entry(display, i++, back_r, back_g, back_b,
output_encoding == P_LINEAR ? 65535U : 255U, output_encoding);
/* For non-opaque input composite on the sRGB background - this
* requires inverting the encoding for each component. The input
* is still converted to the sRGB encoding because this is a
* reasonable approximate to the logarithmic curve of human
* visual sensitivity, at least over the narrow range which PNG
* represents. Consequently 'G' is always sRGB encoded, while
* 'A' is linear. We need the linear background colors.
*/
if (output_encoding == P_sRGB) /* else already linear */
{
/* This may produce a value not exactly matching the
* background, but that's ok because these numbers are only
* used when alpha != 0
*/
back_r = png_sRGB_table[back_r];
back_g = png_sRGB_table[back_g];
back_b = png_sRGB_table[back_b];
}
for (a=1; a<5; ++a)
{
unsigned int g;
/* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
* by an 8-bit alpha value (0..255).
*/
png_uint_32 alpha = 51 * a;
png_uint_32 back_rx = (255-alpha) * back_r;
png_uint_32 back_gx = (255-alpha) * back_g;
png_uint_32 back_bx = (255-alpha) * back_b;
for (g=0; g<6; ++g)
{
png_uint_32 gray = png_sRGB_table[g*51] * alpha;
png_create_colormap_entry(display, i++,
PNG_sRGB_FROM_LINEAR(gray + back_rx),
PNG_sRGB_FROM_LINEAR(gray + back_gx),
PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
}
}
cmap_entries = i;
output_processing = PNG_CMAP_GA;
}
}
break;
case PNG_COLOR_TYPE_RGB:
case PNG_COLOR_TYPE_RGB_ALPHA:
/* Exclude the case where the output is gray; we can always handle this
* with the cases above.
*/
if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
{
/* The color-map will be grayscale, so we may as well convert the
* input RGB values to a simple grayscale and use the grayscale
* code above.
*
* NOTE: calling this apparently damages the recognition of the
* transparent color in background color handling; call
* png_set_tRNS_to_alpha before png_set_background_fixed.
*/
png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
-1);
data_encoding = P_sRGB;
/* The output will now be one or two 8-bit gray or gray+alpha
* channels. The more complex case arises when the input has alpha.
*/
if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0) &&
(output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
/* Both input and output have an alpha channel, so no background
* processing is required; just map the GA bytes to the right
* color-map entry.
*/
expand_tRNS = 1;
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb[ga] color-map: too few entries");
cmap_entries = make_ga_colormap(display);
background_index = PNG_CMAP_GA_BACKGROUND;
output_processing = PNG_CMAP_GA;
}
else
{
/* Either the input or the output has no alpha channel, so there
* will be no non-opaque pixels in the color-map; it will just be
* grayscale.
*/
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb[gray] color-map: too few entries");
/* Ideally this code would use libpng to do the gamma correction,
* but if an input alpha channel is to be removed we will hit the
* libpng bug in gamma+compose+rgb-to-gray (the double gamma
* correction bug). Fix this by dropping the gamma correction in
* this case and doing it in the palette; this will result in
* duplicate palette entries, but that's better than the
* alternative of double gamma correction.
*/
if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0) &&
png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
{
cmap_entries = make_gray_file_colormap(display);
data_encoding = P_FILE;
}
else
cmap_entries = make_gray_colormap(display);
/* But if the input has alpha or transparency it must be removed
*/
if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0)
{
png_color_16 c;
png_uint_32 gray = back_g;
/* We need to ensure that the application background exists in
* the colormap and that completely transparent pixels map to
* it. Achieve this simply by ensuring that the entry
* selected for the background really is the background color.
*/
if (data_encoding == P_FILE) /* from the fixup above */
{
/* The app supplied a gray which is in output_encoding, we
* need to convert it to a value of the input (P_FILE)
* encoding then set this palette entry to the required
* output encoding.
*/
if (output_encoding == P_sRGB)
gray = png_sRGB_table[gray]; /* now P_LINEAR */
gray = PNG_DIV257(png_gamma_16bit_correct(gray,
png_ptr->colorspace.gamma)); /* now P_FILE */
/* And make sure the corresponding palette entry contains
* exactly the required sRGB value.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 0/*unused*/, output_encoding);
}
else if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(gray * 255);
/* And make sure the corresponding palette entry matches.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 0/*unused*/, P_LINEAR);
}
/* The background passed to libpng, however, must be the
* output (normally sRGB) value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
/* NOTE: the following is apparently a bug in libpng. Without
* it the transparent color recognition in
* png_set_background_fixed seems to go wrong.
*/
expand_tRNS = 1;
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
}
output_processing = PNG_CMAP_NONE;
}
}
else /* output is color */
{
/* We could use png_quantize here so long as there is no transparent
* color or alpha; png_quantize ignores alpha. Easier overall just
* to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
* Consequently we always want libpng to produce sRGB data.
*/
data_encoding = P_sRGB;
/* Is there any transparency or alpha? */
if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0)
{
/* Is there alpha in the output too? If so all four channels are
* processed into a special RGB cube with alpha support.
*/
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
png_uint_32 r;
if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
png_error(png_ptr, "rgb+alpha color-map: too few entries");
cmap_entries = make_rgb_colormap(display);
/* Add a transparent entry. */
png_create_colormap_entry(display, cmap_entries, 255, 255,
255, 0, P_sRGB);
/* This is stored as the background index for the processing
* algorithm.
*/
background_index = cmap_entries++;
/* Add 27 r,g,b entries each with alpha 0.5. */
for (r=0; r<256; r = (r << 1) | 0x7f)
{
png_uint_32 g;
for (g=0; g<256; g = (g << 1) | 0x7f)
{
png_uint_32 b;
/* This generates components with the values 0, 127 and
* 255
*/
for (b=0; b<256; b = (b << 1) | 0x7f)
png_create_colormap_entry(display, cmap_entries++,
r, g, b, 128, P_sRGB);
}
}
expand_tRNS = 1;
output_processing = PNG_CMAP_RGB_ALPHA;
}
else
{
/* Alpha/transparency must be removed. The background must
* exist in the color map (achieved by setting adding it after
* the 666 color-map). If the standard processing code will
* pick up this entry automatically that's all that is
* required; libpng can be called to do the background
* processing.
*/
unsigned int sample_size =
PNG_IMAGE_SAMPLE_SIZE(output_format);
png_uint_32 r, g, b; /* sRGB background */
if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
png_error(png_ptr, "rgb-alpha color-map: too few entries");
cmap_entries = make_rgb_colormap(display);
png_create_colormap_entry(display, cmap_entries, back_r,
back_g, back_b, 0/*unused*/, output_encoding);
if (output_encoding == P_LINEAR)
{
r = PNG_sRGB_FROM_LINEAR(back_r * 255);
g = PNG_sRGB_FROM_LINEAR(back_g * 255);
b = PNG_sRGB_FROM_LINEAR(back_b * 255);
}
else
{
r = back_r;
g = back_g;
b = back_g;
}
/* Compare the newly-created color-map entry with the one the
* PNG_CMAP_RGB algorithm will use. If the two entries don't
* match, add the new one and set this as the background
* index.
*/
if (memcmp((png_const_bytep)display->colormap +
sample_size * cmap_entries,
(png_const_bytep)display->colormap +
sample_size * PNG_RGB_INDEX(r,g,b),
sample_size) != 0)
{
/* The background color must be added. */
background_index = cmap_entries++;
/* Add 27 r,g,b entries each with created by composing with
* the background at alpha 0.5.
*/
for (r=0; r<256; r = (r << 1) | 0x7f)
{
for (g=0; g<256; g = (g << 1) | 0x7f)
{
/* This generates components with the values 0, 127
* and 255
*/
for (b=0; b<256; b = (b << 1) | 0x7f)
png_create_colormap_entry(display, cmap_entries++,
png_colormap_compose(display, r, P_sRGB, 128,
back_r, output_encoding),
png_colormap_compose(display, g, P_sRGB, 128,
back_g, output_encoding),
png_colormap_compose(display, b, P_sRGB, 128,
back_b, output_encoding),
0/*unused*/, output_encoding);
}
}
expand_tRNS = 1;
output_processing = PNG_CMAP_RGB_ALPHA;
}
else /* background color is in the standard color-map */
{
png_color_16 c;
c.index = 0; /*unused*/
c.red = (png_uint_16)back_r;
c.gray = c.green = (png_uint_16)back_g;
c.blue = (png_uint_16)back_b;
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_RGB;
}
}
}
else /* no alpha or transparency in the input */
{
/* Alpha in the output is irrelevant, simply map the opaque input
* pixels to the 6x6x6 color-map.
*/
if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb color-map: too few entries");
cmap_entries = make_rgb_colormap(display);
output_processing = PNG_CMAP_RGB;
}
}
break;
case PNG_COLOR_TYPE_PALETTE:
/* It's already got a color-map. It may be necessary to eliminate the
* tRNS entries though.
*/
{
unsigned int num_trans = png_ptr->num_trans;
png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
png_const_colorp colormap = png_ptr->palette;
const int do_background = trans != NULL &&
(output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
unsigned int i;
/* Just in case: */
if (trans == NULL)
num_trans = 0;
output_processing = PNG_CMAP_NONE;
data_encoding = P_FILE; /* Don't change from color-map indices */
cmap_entries = png_ptr->num_palette;
if (cmap_entries > 256)
cmap_entries = 256;
if (cmap_entries > image->colormap_entries)
png_error(png_ptr, "palette color-map: too few entries");
for (i=0; i < cmap_entries; ++i)
{
if (do_background != 0 && i < num_trans && trans[i] < 255)
{
if (trans[i] == 0)
png_create_colormap_entry(display, i, back_r, back_g,
back_b, 0, output_encoding);
else
{
/* Must compose the PNG file color in the color-map entry
* on the sRGB color in 'back'.
*/
png_create_colormap_entry(display, i,
png_colormap_compose(display, colormap[i].red, P_FILE,
trans[i], back_r, output_encoding),
png_colormap_compose(display, colormap[i].green, P_FILE,
trans[i], back_g, output_encoding),
png_colormap_compose(display, colormap[i].blue, P_FILE,
trans[i], back_b, output_encoding),
output_encoding == P_LINEAR ? trans[i] * 257U :
trans[i],
output_encoding);
}
}
else
png_create_colormap_entry(display, i, colormap[i].red,
colormap[i].green, colormap[i].blue,
i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
}
/* The PNG data may have indices packed in fewer than 8 bits, it
* must be expanded if so.
*/
if (png_ptr->bit_depth < 8)
png_set_packing(png_ptr);
}
break;
default:
png_error(png_ptr, "invalid PNG color type");
/*NOT REACHED*/
break;
}
/* Now deal with the output processing */
if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
(png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
png_set_tRNS_to_alpha(png_ptr);
switch (data_encoding)
{
default:
png_error(png_ptr, "bad data option (internal error)");
break;
case P_sRGB:
/* Change to 8-bit sRGB */
png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
/* FALL THROUGH */
case P_FILE:
if (png_ptr->bit_depth > 8)
png_set_scale_16(png_ptr);
break;
}
if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
png_error(png_ptr, "color map overflow (BAD internal error)");
image->colormap_entries = cmap_entries;
/* Double check using the recorded background index */
switch (output_processing)
{
case PNG_CMAP_NONE:
if (background_index != PNG_CMAP_NONE_BACKGROUND)
goto bad_background;
break;
case PNG_CMAP_GA:
if (background_index != PNG_CMAP_GA_BACKGROUND)
goto bad_background;
break;
case PNG_CMAP_TRANS:
if (background_index >= cmap_entries ||
background_index != PNG_CMAP_TRANS_BACKGROUND)
goto bad_background;
break;
case PNG_CMAP_RGB:
if (background_index != PNG_CMAP_RGB_BACKGROUND)
goto bad_background;
break;
case PNG_CMAP_RGB_ALPHA:
if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
goto bad_background;
break;
default:
png_error(png_ptr, "bad processing option (internal error)");
bad_background:
png_error(png_ptr, "bad background index (internal error)");
}
display->colormap_processing = output_processing;
return 1/*ok*/;
}
/* The final part of the color-map read called from png_image_finish_read. */
static int
png_image_read_and_map(png_voidp argument)
{
png_image_read_control *display = png_voidcast(png_image_read_control*,
argument);
png_imagep image = display->image;
png_structrp png_ptr = image->opaque->png_ptr;
int passes;
/* Called when the libpng data must be transformed into the color-mapped
* form. There is a local row buffer in display->local and this routine must
* do the interlace handling.
*/
switch (png_ptr->interlaced)
{
case PNG_INTERLACE_NONE:
passes = 1;
break;
case PNG_INTERLACE_ADAM7:
passes = PNG_INTERLACE_ADAM7_PASSES;
break;
default:
png_error(png_ptr, "unknown interlace type");
}
{
png_uint_32 height = image->height;
png_uint_32 width = image->width;
int proc = display->colormap_processing;
png_bytep first_row = png_voidcast(png_bytep, display->first_row);
ptrdiff_t step_row = display->row_bytes;
int pass;
for (pass = 0; pass < passes; ++pass)
{
unsigned int startx, stepx, stepy;
png_uint_32 y;
if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
{
/* The row may be empty for a short image: */
if (PNG_PASS_COLS(width, pass) == 0)
continue;
startx = PNG_PASS_START_COL(pass);
stepx = PNG_PASS_COL_OFFSET(pass);
y = PNG_PASS_START_ROW(pass);
stepy = PNG_PASS_ROW_OFFSET(pass);
}
src/Source/LibPNG/pngread.c view on Meta::CPAN
}
for (; y<height; y += stepy)
{
png_bytep inrow = png_voidcast(png_bytep, display->local_row);
png_bytep outrow;
png_const_bytep end_row;
/* Read the row, which is packed: */
png_read_row(png_ptr, inrow, NULL);
outrow = png_voidcast(png_bytep, display->first_row);
outrow += y * step_row;
end_row = outrow + width * channels;
/* Now do the composition on each pixel in this row. */
outrow += startx;
for (; outrow < end_row; outrow += stepx)
{
png_byte alpha = inrow[channels];
if (alpha > 0) /* else no change to the output */
{
unsigned int c;
for (c=0; c<channels; ++c)
{
png_uint_32 component = inrow[c];
if (alpha < 255) /* else just use component */
{
/* This is PNG_OPTIMIZED_ALPHA, the component value
* is a linear 8-bit value. Combine this with the
* current outrow[c] value which is sRGB encoded.
* Arithmetic here is 16-bits to preserve the output
* values correctly.
*/
component *= 257*255; /* =65535 */
component += (255-alpha)*png_sRGB_table[outrow[c]];
/* So 'component' is scaled by 255*65535 and is
* therefore appropriate for the sRGB to linear
* conversion table.
*/
component = PNG_sRGB_FROM_LINEAR(component);
}
outrow[c] = (png_byte)component;
}
}
inrow += channels+1; /* components and alpha channel */
}
}
}
}
return 1;
}
/* The do_local_background case; called when all the following transforms are to
* be done:
*
* PNG_RGB_TO_GRAY
* PNG_COMPOSITE
* PNG_GAMMA
*
* This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
* PNG_COMPOSITE code performs gamma correction, so we get double gamma
* correction. The fix-up is to prevent the PNG_COMPOSITE operation from
* happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
* row and handles the removal or pre-multiplication of the alpha channel.
*/
static int
png_image_read_background(png_voidp argument)
{
png_image_read_control *display = png_voidcast(png_image_read_control*,
argument);
png_imagep image = display->image;
png_structrp png_ptr = image->opaque->png_ptr;
png_inforp info_ptr = image->opaque->info_ptr;
png_uint_32 height = image->height;
png_uint_32 width = image->width;
int pass, passes;
/* Double check the convoluted logic below. We expect to get here with
* libpng doing rgb to gray and gamma correction but background processing
* left to the png_image_read_background function. The rows libpng produce
* might be 8 or 16-bit but should always have two channels; gray plus alpha.
*/
if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
png_error(png_ptr, "lost rgb to gray");
if ((png_ptr->transformations & PNG_COMPOSE) != 0)
png_error(png_ptr, "unexpected compose");
if (png_get_channels(png_ptr, info_ptr) != 2)
png_error(png_ptr, "lost/gained channels");
/* Expect the 8-bit case to always remove the alpha channel */
if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
(image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
png_error(png_ptr, "unexpected 8-bit transformation");
switch (png_ptr->interlaced)
{
case PNG_INTERLACE_NONE:
passes = 1;
break;
case PNG_INTERLACE_ADAM7:
passes = PNG_INTERLACE_ADAM7_PASSES;
break;
default:
png_error(png_ptr, "unknown interlace type");
}
/* Use direct access to info_ptr here because otherwise the simplified API
* would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
* checking the value after libpng expansions, not the original value in the
* PNG.
*/
switch (info_ptr->bit_depth)
{
default:
png_error(png_ptr, "unexpected bit depth");
break;
case 8:
/* 8-bit sRGB gray values with an alpha channel; the alpha channel is
* to be removed by composing on a background: either the row if
* display->background is NULL or display->background->green if not.
* Unlike the code above ALPHA_OPTIMIZED has *not* been done.
*/
{
png_bytep first_row = png_voidcast(png_bytep, display->first_row);
ptrdiff_t step_row = display->row_bytes;
for (pass = 0; pass < passes; ++pass)
{
png_bytep row = png_voidcast(png_bytep,
display->first_row);
unsigned int startx, stepx, stepy;
png_uint_32 y;
if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
{
/* The row may be empty for a short image: */
if (PNG_PASS_COLS(width, pass) == 0)
continue;
startx = PNG_PASS_START_COL(pass);
stepx = PNG_PASS_COL_OFFSET(pass);
y = PNG_PASS_START_ROW(pass);
stepy = PNG_PASS_ROW_OFFSET(pass);
}
else
{
y = 0;
startx = 0;
stepx = stepy = 1;
}
if (display->background == NULL)
{
for (; y<height; y += stepy)
{
png_bytep inrow = png_voidcast(png_bytep,
display->local_row);
png_bytep outrow = first_row + y * step_row;
png_const_bytep end_row = outrow + width;
/* Read the row, which is packed: */
png_read_row(png_ptr, inrow, NULL);
/* Now do the composition on each pixel in this row. */
outrow += startx;
for (; outrow < end_row; outrow += stepx)
{
png_byte alpha = inrow[1];
if (alpha > 0) /* else no change to the output */
{
png_uint_32 component = inrow[0];
if (alpha < 255) /* else just use component */
{
/* Since PNG_OPTIMIZED_ALPHA was not set it is
* necessary to invert the sRGB transfer
* function and multiply the alpha out.
*/
component = png_sRGB_table[component] * alpha;
component += png_sRGB_table[outrow[0]] *
(255-alpha);
component = PNG_sRGB_FROM_LINEAR(component);
}
outrow[0] = (png_byte)component;
}
inrow += 2; /* gray and alpha channel */
}
}
}
else /* constant background value */
{
png_byte background8 = display->background->green;
png_uint_16 background = png_sRGB_table[background8];
for (; y<height; y += stepy)
{
png_bytep inrow = png_voidcast(png_bytep,
display->local_row);
png_bytep outrow = first_row + y * step_row;
png_const_bytep end_row = outrow + width;
/* Read the row, which is packed: */
png_read_row(png_ptr, inrow, NULL);
/* Now do the composition on each pixel in this row. */
outrow += startx;
for (; outrow < end_row; outrow += stepx)
{
png_byte alpha = inrow[1];
if (alpha > 0) /* else use background */
{
png_uint_32 component = inrow[0];
if (alpha < 255) /* else just use component */
{
component = png_sRGB_table[component] * alpha;
component += background * (255-alpha);
component = PNG_sRGB_FROM_LINEAR(component);
}
outrow[0] = (png_byte)component;
}
else
outrow[0] = background8;
inrow += 2; /* gray and alpha channel */
}
row += display->row_bytes;
}
}
}
}
break;
case 16:
/* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
* still be done and, maybe, the alpha channel removed. This code also
* handles the alpha-first option.
*/
{
png_uint_16p first_row = png_voidcast(png_uint_16p,
display->first_row);
/* The division by two is safe because the caller passed in a
* stride which was multiplied by 2 (below) to get row_bytes.
*/
ptrdiff_t step_row = display->row_bytes / 2;
int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
unsigned int outchannels = 1+preserve_alpha;
int swap_alpha = 0;
# ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
if (preserve_alpha != 0 &&
(image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
swap_alpha = 1;
# endif
for (pass = 0; pass < passes; ++pass)
{
unsigned int startx, stepx, stepy;
png_uint_32 y;
/* The 'x' start and step are adjusted to output components here.
*/
if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
{
/* The row may be empty for a short image: */
if (PNG_PASS_COLS(width, pass) == 0)
continue;
startx = PNG_PASS_START_COL(pass) * outchannels;
stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
y = PNG_PASS_START_ROW(pass);
stepy = PNG_PASS_ROW_OFFSET(pass);
}
else
{
y = 0;
startx = 0;
stepx = outchannels;
stepy = 1;
}
for (; y<height; y += stepy)
{
png_const_uint_16p inrow;
png_uint_16p outrow = first_row + y*step_row;
png_uint_16p end_row = outrow + width * outchannels;
/* Read the row, which is packed: */
png_read_row(png_ptr, png_voidcast(png_bytep,
display->local_row), NULL);
inrow = png_voidcast(png_const_uint_16p, display->local_row);
/* Now do the pre-multiplication on each pixel in this row.
*/
outrow += startx;
for (; outrow < end_row; outrow += stepx)
{
png_uint_32 component = inrow[0];
png_uint_16 alpha = inrow[1];
if (alpha > 0) /* else 0 */
{
if (alpha < 65535) /* else just use component */
{
component *= alpha;
component += 32767;
component /= 65535;
}
}
else
component = 0;
outrow[swap_alpha] = (png_uint_16)component;
if (preserve_alpha != 0)
outrow[1 ^ swap_alpha] = alpha;
inrow += 2; /* components and alpha channel */
}
}
}
}
break;
}
return 1;
}
/* The guts of png_image_finish_read as a png_safe_execute callback. */
static int
png_image_read_direct(png_voidp argument)
{
png_image_read_control *display = png_voidcast(png_image_read_control*,
argument);
png_imagep image = display->image;
png_structrp png_ptr = image->opaque->png_ptr;
png_inforp info_ptr = image->opaque->info_ptr;
png_uint_32 format = image->format;
int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
int do_local_compose = 0;
int do_local_background = 0; /* to avoid double gamma correction bug */
int passes = 0;
/* Add transforms to ensure the correct output format is produced then check
* that the required implementation support is there. Always expand; always
* need 8 bits minimum, no palette and expanded tRNS.
*/
png_set_expand(png_ptr);
/* Now check the format to see if it was modified. */
{
png_uint_32 base_format = png_image_format(png_ptr) &
~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
png_uint_32 change = format ^ base_format;
png_fixed_point output_gamma;
int mode; /* alpha mode */
/* Do this first so that we have a record if rgb to gray is happening. */
if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
{
/* gray<->color transformation required. */
if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
png_set_gray_to_rgb(png_ptr);
else
{
/* libpng can't do both rgb to gray and
* background/pre-multiplication if there is also significant gamma
* correction, because both operations require linear colors and
* the code only supports one transform doing the gamma correction.
* Handle this by doing the pre-multiplication or background
* operation in this code, if necessary.
*
* TODO: fix this by rewriting pngrtran.c (!)
*
* For the moment (given that fixing this in pngrtran.c is an
* enormous change) 'do_local_background' is used to indicate that
* the problem exists.
*/
if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
do_local_background = 1/*maybe*/;
png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
}
change &= ~PNG_FORMAT_FLAG_COLOR;
}
/* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
*/
{
png_fixed_point input_gamma_default;
if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
(image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
input_gamma_default = PNG_GAMMA_LINEAR;
else
input_gamma_default = PNG_DEFAULT_sRGB;
/* Call png_set_alpha_mode to set the default for the input gamma; the
* output gamma is set by a second call below.
*/
png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
}
if (linear != 0)
{
/* If there *is* an alpha channel in the input it must be multiplied
* out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
*/
if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
mode = PNG_ALPHA_STANDARD; /* associated alpha */
else
mode = PNG_ALPHA_PNG;
output_gamma = PNG_GAMMA_LINEAR;
}
else
{
mode = PNG_ALPHA_PNG;
output_gamma = PNG_DEFAULT_sRGB;
}
/* If 'do_local_background' is set check for the presence of gamma
* correction; this is part of the work-round for the libpng bug
* described above.
*
* TODO: fix libpng and remove this.
*/
if (do_local_background != 0)
{
png_fixed_point gtest;
/* This is 'png_gamma_threshold' from pngrtran.c; the test used for
* gamma correction, the screen gamma hasn't been set on png_struct
* yet; it's set below. png_struct::gamma, however, is set to the
* final value.
*/
if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
do_local_background = 0;
else if (mode == PNG_ALPHA_STANDARD)
{
do_local_background = 2/*required*/;
mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
}
/* else leave as 1 for the checks below */
}
/* If the bit-depth changes then handle that here. */
if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
{
if (linear != 0 /*16-bit output*/)
png_set_expand_16(png_ptr);
else /* 8-bit output */
png_set_scale_16(png_ptr);
change &= ~PNG_FORMAT_FLAG_LINEAR;
}
/* Now the background/alpha channel changes. */
if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
{
/* Removing an alpha channel requires composition for the 8-bit
* formats; for the 16-bit it is already done, above, by the
* pre-multiplication and the channel just needs to be stripped.
*/
if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
/* If RGB->gray is happening the alpha channel must be left and the
* operation completed locally.
*
* TODO: fix libpng and remove this.
*/
if (do_local_background != 0)
do_local_background = 2/*required*/;
/* 16-bit output: just remove the channel */
else if (linear != 0) /* compose on black (well, pre-multiply) */
png_set_strip_alpha(png_ptr);
/* 8-bit output: do an appropriate compose */
else if (display->background != NULL)
{
png_color_16 c;
c.index = 0; /*unused*/
c.red = display->background->red;
c.green = display->background->green;
c.blue = display->background->blue;
c.gray = display->background->green;
/* This is always an 8-bit sRGB value, using the 'green' channel
* for gray is much better than calculating the luminance here;
* we can get off-by-one errors in that calculation relative to
* the app expectations and that will show up in transparent
* pixels.
*/
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
}
else /* compose on row: implemented below. */
{
do_local_compose = 1;
/* This leaves the alpha channel in the output, so it has to be
* removed by the code below. Set the encoding to the 'OPTIMIZE'
* one so the code only has to hack on the pixels that require
* composition.
*/
mode = PNG_ALPHA_OPTIMIZED;
}
}
else /* output needs an alpha channel */
{
/* This is tricky because it happens before the swap operation has
* been accomplished; however, the swap does *not* swap the added
* alpha channel (weird API), so it must be added in the correct
* place.
*/
png_uint_32 filler; /* opaque filler */
int where;
if (linear != 0)
filler = 65535;
else
filler = 255;
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
{
where = PNG_FILLER_BEFORE;
change &= ~PNG_FORMAT_FLAG_AFIRST;
}
else
# endif
where = PNG_FILLER_AFTER;
png_set_add_alpha(png_ptr, filler, where);
}
/* This stops the (irrelevant) call to swap_alpha below. */
change &= ~PNG_FORMAT_FLAG_ALPHA;
}
/* Now set the alpha mode correctly; this is always done, even if there is
* no alpha channel in either the input or the output because it correctly
* sets the output gamma.
*/
png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
# ifdef PNG_FORMAT_BGR_SUPPORTED
if ((change & PNG_FORMAT_FLAG_BGR) != 0)
{
/* Check only the output format; PNG is never BGR; don't do this if
* the output is gray, but fix up the 'format' value in that case.
*/
if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
png_set_bgr(png_ptr);
else
format &= ~PNG_FORMAT_FLAG_BGR;
change &= ~PNG_FORMAT_FLAG_BGR;
}
# endif
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
{
/* Only relevant if there is an alpha channel - it's particularly
* important to handle this correctly because do_local_compose may
* be set above and then libpng will keep the alpha channel for this
* code to remove.
*/
if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
/* Disable this if doing a local background,
* TODO: remove this when local background is no longer required.
*/
if (do_local_background != 2)
png_set_swap_alpha(png_ptr);
}
else
format &= ~PNG_FORMAT_FLAG_AFIRST;
change &= ~PNG_FORMAT_FLAG_AFIRST;
}
# endif
/* If the *output* is 16-bit then we need to check for a byte-swap on this
* architecture.
*/
if (linear != 0)
{
PNG_CONST png_uint_16 le = 0x0001;
if ((*(png_const_bytep) & le) != 0)
png_set_swap(png_ptr);
}
/* If change is not now 0 some transformation is missing - error out. */
if (change != 0)
png_error(png_ptr, "png_read_image: unsupported transformation");
}
PNG_SKIP_CHUNKS(png_ptr);
/* Update the 'info' structure and make sure the result is as required; first
* make sure to turn on the interlace handling if it will be required
* (because it can't be turned on *after* the call to png_read_update_info!)
*
* TODO: remove the do_local_background fixup below.
*/
if (do_local_compose == 0 && do_local_background != 2)
passes = png_set_interlace_handling(png_ptr);
png_read_update_info(png_ptr, info_ptr);
{
png_uint_32 info_format = 0;
if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
info_format |= PNG_FORMAT_FLAG_COLOR;
if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
{
/* do_local_compose removes this channel below. */
if (do_local_compose == 0)
{
/* do_local_background does the same if required. */
if (do_local_background != 2 ||
(format & PNG_FORMAT_FLAG_ALPHA) != 0)
info_format |= PNG_FORMAT_FLAG_ALPHA;
}
}
else if (do_local_compose != 0) /* internal error */
png_error(png_ptr, "png_image_read: alpha channel lost");
if (info_ptr->bit_depth == 16)
info_format |= PNG_FORMAT_FLAG_LINEAR;
# ifdef PNG_FORMAT_BGR_SUPPORTED
if ((png_ptr->transformations & PNG_BGR) != 0)
info_format |= PNG_FORMAT_FLAG_BGR;
# endif
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (do_local_background == 2)
{
if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
info_format |= PNG_FORMAT_FLAG_AFIRST;
}
if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
(png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
{
if (do_local_background == 2)
png_error(png_ptr, "unexpected alpha swap transformation");
info_format |= PNG_FORMAT_FLAG_AFIRST;
}
# endif
/* This is actually an internal error. */
if (info_format != format)
png_error(png_ptr, "png_read_image: invalid transformations");
}
/* Now read the rows. If do_local_compose is set then it is necessary to use
* a local row buffer. The output will be GA, RGBA or BGRA and must be
* converted to G, RGB or BGR as appropriate. The 'local_row' member of the
* display acts as a flag.
*/
{
png_voidp first_row = display->buffer;
ptrdiff_t row_bytes = display->row_stride;
if (linear != 0)
row_bytes *= 2;
/* The following expression is designed to work correctly whether it gives
* a signed or an unsigned result.
*/
if (row_bytes < 0)
{
char *ptr = png_voidcast(char*, first_row);
ptr += (image->height-1) * (-row_bytes);
first_row = png_voidcast(png_voidp, ptr);
}
display->first_row = first_row;
display->row_bytes = row_bytes;
}
if (do_local_compose != 0)
{
int result;
png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
display->local_row = row;
result = png_safe_execute(image, png_image_read_composite, display);
display->local_row = NULL;
png_free(png_ptr, row);
return result;
}
else if (do_local_background == 2)
{
int result;
png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
display->local_row = row;
result = png_safe_execute(image, png_image_read_background, display);
display->local_row = NULL;
png_free(png_ptr, row);
return result;
}
else
{
png_alloc_size_t row_bytes = display->row_bytes;
while (--passes >= 0)
{
png_uint_32 y = image->height;
png_bytep row = png_voidcast(png_bytep, display->first_row);
while (y-- > 0)
{
png_read_row(png_ptr, row, NULL);
row += row_bytes;
}
}
return 1;
}
}
int PNGAPI
png_image_finish_read(png_imagep image, png_const_colorp background,
void *buffer, png_int_32 row_stride, void *colormap)
{
if (image != NULL && image->version == PNG_IMAGE_VERSION)
{
png_uint_32 check;
if (row_stride == 0)
row_stride = PNG_IMAGE_ROW_STRIDE(*image);
if (row_stride < 0)
check = -row_stride;
else
check = row_stride;
if (image->opaque != NULL && buffer != NULL &&
check >= PNG_IMAGE_ROW_STRIDE(*image))
{
if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
(image->colormap_entries > 0 && colormap != NULL))
{
int result;
png_image_read_control display;
memset(&display, 0, (sizeof display));
display.image = image;
display.buffer = buffer;
display.row_stride = row_stride;
display.colormap = colormap;
display.background = background;
display.local_row = NULL;
/* Choose the correct 'end' routine; for the color-map case all the
* setup has already been done.
*/
if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
result =
png_safe_execute(image, png_image_read_colormap, &display) &&
png_safe_execute(image, png_image_read_colormapped, &display);
else
result =
png_safe_execute(image, png_image_read_direct, &display);
png_image_free(image);
return result;
}
else
return png_image_error(image,
"png_image_finish_read[color-map]: no color-map");
}
else
return png_image_error(image,
"png_image_finish_read: invalid argument");
}
else if (image != NULL)
return png_image_error(image,
"png_image_finish_read: damaged PNG_IMAGE_VERSION");
return 0;
}
#endif /* SIMPLIFIED_READ */
#endif /* READ */
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