Alien-FreeImage
view release on metacpan or search on metacpan
src/Source/LibPNG/example.c view on Meta::CPAN
* then write the result out to the new file. 'background' is not
* necessary when reading the image because the alpha channel is
* preserved; if it were to be removed, for example if we requested
* PNG_FORMAT_RGB, then either a solid background color would have to
* be supplied or the output buffer would have to be initialized to the
* actual background of the image.
*
* The fourth argument to png_image_finish_read is the 'row_stride' -
* this is the number of components allocated for the image in each
* row. It has to be at least as big as the value returned by
* PNG_IMAGE_ROW_STRIDE, but if you just allocate space for the
* default, minimum, size using PNG_IMAGE_SIZE as above you can pass
* zero.
*
* The final argument is a pointer to a buffer for the colormap;
* colormaps have exactly the same format as a row of image pixels (so
* you choose what format to make the colormap by setting
* image.format). A colormap is only returned if
* PNG_FORMAT_FLAG_COLORMAP is also set in image.format, so in this
* case NULL is passed as the final argument. If you do want to force
* all images into an index/color-mapped format then you can use:
*
* PNG_IMAGE_COLORMAP_SIZE(image)
*
* to find the maximum size of the colormap in bytes.
*/
if (buffer != NULL &&
png_image_finish_read(&image, NULL/*background*/, buffer,
0/*row_stride*/, NULL/*colormap*/) != 0)
{
/* Now write the image out to the second argument. In the write
* call 'convert_to_8bit' allows 16-bit data to be squashed down to
* 8 bits; this isn't necessary here because the original read was
* to the 8-bit format.
*/
if (png_image_write_to_file(&image, argv[2], 0/*convert_to_8bit*/,
buffer, 0/*row_stride*/, NULL/*colormap*/) != 0)
{
/* The image has been written successfully. */
exit(0);
}
}
else
{
/* Calling png_free_image is optional unless the simplified API was
* not run to completion. In this case if there wasn't enough
* memory for 'buffer' we didn't complete the read, so we must free
* the image:
*/
if (buffer == NULL)
png_free_image(&image);
else
free(buffer);
}
/* Something went wrong reading or writing the image. libpng stores a
* textual message in the 'png_image' structure:
*/
fprintf(stderr, "pngtopng: error: %s\n", image.message);
exit (1);
}
fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
exit(1);
}
/* That's it ;-) Of course you probably want to do more with PNG files than
* just converting them all to 32-bit RGBA PNG files; you can do that between
* the call to png_image_finish_read and png_image_write_to_file. You can also
* ask for the image data to be presented in a number of different formats. You
* do this by simply changing the 'format' parameter set before allocating the
* buffer.
*
* The format parameter consists of five flags that define various aspects of
* the image, you can simply add these together to get the format or you can use
* one of the predefined macros from png.h (as above):
*
* PNG_FORMAT_FLAG_COLOR: if set the image will have three color components per
* pixel (red, green and blue), if not set the image will just have one
* luminance (grayscale) component.
*
* PNG_FORMAT_FLAG_ALPHA: if set each pixel in the image will have an additional
* alpha value; a linear value that describes the degree the image pixel
* covers (overwrites) the contents of the existing pixel on the display.
*
* PNG_FORMAT_FLAG_LINEAR: if set the components of each pixel will be returned
* as a series of 16-bit linear values, if not set the components will be
* returned as a series of 8-bit values encoded according to the 'sRGB'
* standard. The 8-bit format is the normal format for images intended for
* direct display, because almost all display devices do the inverse of the
* sRGB transformation to the data they receive. The 16-bit format is more
* common for scientific data and image data that must be further processed;
* because it is linear simple math can be done on the component values.
* Regardless of the setting of this flag the alpha channel is always linear,
* although it will be 8 bits or 16 bits wide as specified by the flag.
*
* PNG_FORMAT_FLAG_BGR: if set the components of a color pixel will be returned
* in the order blue, then green, then red. If not set the pixel components
* are in the order red, then green, then blue.
*
* PNG_FORMAT_FLAG_AFIRST: if set the alpha channel (if present) precedes the
* color or grayscale components. If not set the alpha channel follows the
* components.
*
* You do not have to read directly from a file. You can read from memory or,
* on systems that support it, from a <stdio.h> FILE*. This is controlled by
* the particular png_image_read_from_ function you call at the start. Likewise
* on write you can write to a FILE* if your system supports it. Check the
* macro PNG_STDIO_SUPPORTED to see if stdio support has been included in your
* libpng build.
*
* If you read 16-bit (PNG_FORMAT_FLAG_LINEAR) data you may need to write it in
* the 8-bit format for display. You do this by setting the convert_to_8bit
* flag to 'true'.
*
* Don't repeatedly convert between the 8-bit and 16-bit forms. There is
* significant data loss when 16-bit data is converted to the 8-bit encoding and
* the current libpng implementation of conversion to 16-bit is also
* significantly lossy. The latter will be fixed in the future, but the former
* is unavoidable - the 8-bit format just doesn't have enough resolution.
*/
/* If your program needs more information from the PNG data it reads, or if you
src/Source/LibPNG/example.c view on Meta::CPAN
* you have created the png_ptr, so that libpng knows your application
* has read that many bytes from the start of the file. Make sure you
* don't call png_set_sig_bytes() with more than 8 bytes read or give it
* an incorrect number of bytes read, or you will either have read too
* many bytes (your fault), or you are telling libpng to read the wrong
* number of magic bytes (also your fault).
*
* Many applications already read the first 2 or 4 bytes from the start
* of the image to determine the file type, so it would be easiest just
* to pass the bytes to png_sig_cmp() or even skip that if you know
* you have a PNG file, and call png_set_sig_bytes().
*/
#define PNG_BYTES_TO_CHECK 4
int check_if_png(char *file_name, FILE **fp)
{
char buf[PNG_BYTES_TO_CHECK];
/* Open the prospective PNG file. */
if ((*fp = fopen(file_name, "rb")) == NULL)
return 0;
/* Read in some of the signature bytes */
if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK)
return 0;
/* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
Return nonzero (true) if they match */
return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
}
/* Read a PNG file. You may want to return an error code if the read
* fails (depending upon the failure). There are two "prototypes" given
* here - one where we are given the filename, and we need to open the
* file, and the other where we are given an open file (possibly with
* some or all of the magic bytes read - see comments above).
*/
#ifdef open_file /* prototype 1 */
void read_png(char *file_name) /* We need to open the file */
{
png_structp png_ptr;
png_infop info_ptr;
unsigned int sig_read = 0;
png_uint_32 width, height;
int bit_depth, color_type, interlace_type;
FILE *fp;
if ((fp = fopen(file_name, "rb")) == NULL)
return (ERROR);
#else no_open_file /* prototype 2 */
void read_png(FILE *fp, unsigned int sig_read) /* File is already open */
{
png_structp png_ptr;
png_infop info_ptr;
png_uint_32 width, height;
int bit_depth, color_type, interlace_type;
#endif no_open_file /* Only use one prototype! */
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
* you can supply NULL for the last three parameters. We also supply the
* the compiler header file version, so that we know if the application
* was compiled with a compatible version of the library. REQUIRED
*/
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
png_voidp user_error_ptr, user_error_fn, user_warning_fn);
if (png_ptr == NULL)
{
fclose(fp);
return (ERROR);
}
/* Allocate/initialize the memory for image information. REQUIRED. */
info_ptr = png_create_info_struct(png_ptr);
if (info_ptr == NULL)
{
fclose(fp);
png_destroy_read_struct(&png_ptr, NULL, NULL);
return (ERROR);
}
/* Set error handling if you are using the setjmp/longjmp method (this is
* the normal method of doing things with libpng). REQUIRED unless you
* set up your own error handlers in the png_create_read_struct() earlier.
*/
if (setjmp(png_jmpbuf(png_ptr)))
{
/* Free all of the memory associated with the png_ptr and info_ptr */
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
fclose(fp);
/* If we get here, we had a problem reading the file */
return (ERROR);
}
/* One of the following I/O initialization methods is REQUIRED */
#ifdef streams /* PNG file I/O method 1 */
/* Set up the input control if you are using standard C streams */
png_init_io(png_ptr, fp);
#else no_streams /* PNG file I/O method 2 */
/* If you are using replacement read functions, instead of calling
* png_init_io() here you would call:
*/
png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn);
/* where user_io_ptr is a structure you want available to the callbacks */
#endif no_streams /* Use only one I/O method! */
/* If we have already read some of the signature */
png_set_sig_bytes(png_ptr, sig_read);
#ifdef hilevel
/*
* If you have enough memory to read in the entire image at once,
* and you need to specify only transforms that can be controlled
* with one of the PNG_TRANSFORM_* bits (this presently excludes
* quantizing, filling, setting background, and doing gamma
* adjustment), then you can read the entire image (including
* pixels) into the info structure with this call:
src/Source/LibPNG/example.c view on Meta::CPAN
row_pointers[row] = NULL;
for (row = 0; row < height; row++)
row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
info_ptr));
/* Now it's time to read the image. One of these methods is REQUIRED */
#ifdef entire /* Read the entire image in one go */
png_read_image(png_ptr, row_pointers);
#else no_entire /* Read the image one or more scanlines at a time */
/* The other way to read images - deal with interlacing: */
for (pass = 0; pass < number_passes; pass++)
{
#ifdef single /* Read the image a single row at a time */
for (y = 0; y < height; y++)
{
png_read_rows(png_ptr, &row_pointers[y], NULL, 1);
}
#else no_single /* Read the image several rows at a time */
for (y = 0; y < height; y += number_of_rows)
{
#ifdef sparkle /* Read the image using the "sparkle" effect. */
png_read_rows(png_ptr, &row_pointers[y], NULL,
number_of_rows);
#else no_sparkle /* Read the image using the "rectangle" effect */
png_read_rows(png_ptr, NULL, &row_pointers[y],
number_of_rows);
#endif no_sparkle /* Use only one of these two methods */
}
/* If you want to display the image after every pass, do so here */
#endif no_single /* Use only one of these two methods */
}
#endif no_entire /* Use only one of these two methods */
/* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
png_read_end(png_ptr, info_ptr);
#endif hilevel
/* At this point you have read the entire image */
/* Clean up after the read, and free any memory allocated - REQUIRED */
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
/* Close the file */
fclose(fp);
/* That's it */
return (OK);
}
/* Progressively read a file */
int
initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
{
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
* you can supply NULL for the last three parameters. We also check that
* the library version is compatible in case we are using dynamically
* linked libraries.
*/
*png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
png_voidp user_error_ptr, user_error_fn, user_warning_fn);
if (*png_ptr == NULL)
{
*info_ptr = NULL;
return (ERROR);
}
*info_ptr = png_create_info_struct(png_ptr);
if (*info_ptr == NULL)
{
png_destroy_read_struct(png_ptr, info_ptr, NULL);
return (ERROR);
}
if (setjmp(png_jmpbuf((*png_ptr))))
{
png_destroy_read_struct(png_ptr, info_ptr, NULL);
return (ERROR);
}
/* This one's new. You will need to provide all three
* function callbacks, even if you aren't using them all.
* If you aren't using all functions, you can specify NULL
* parameters. Even when all three functions are NULL,
* you need to call png_set_progressive_read_fn().
* These functions shouldn't be dependent on global or
* static variables if you are decoding several images
* simultaneously. You should store stream specific data
* in a separate struct, given as the second parameter,
* and retrieve the pointer from inside the callbacks using
* the function png_get_progressive_ptr(png_ptr).
*/
png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
info_callback, row_callback, end_callback);
return (OK);
}
int
process_data(png_structp *png_ptr, png_infop *info_ptr,
png_bytep buffer, png_uint_32 length)
{
if (setjmp(png_jmpbuf((*png_ptr))))
{
/* Free the png_ptr and info_ptr memory on error */
png_destroy_read_struct(png_ptr, info_ptr, NULL);
return (ERROR);
}
/* This one's new also. Simply give it chunks of data as
* they arrive from the data stream (in order, of course).
* On segmented machines, don't give it any more than 64K.
* The library seems to run fine with sizes of 4K, although
src/Source/LibPNG/example.c view on Meta::CPAN
#ifdef PNG_READ_INTERLACING_SUPPORTED
/* If both rows are allocated then copy the new row
* data to the corresponding row data.
*/
if ((old_row != NULL) && (new_row != NULL))
png_progressive_combine_row(png_ptr, old_row, new_row);
/*
* The rows and passes are called in order, so you don't really
* need the row_num and pass, but I'm supplying them because it
* may make your life easier.
*
* For the non-NULL rows of interlaced images, you must call
* png_progressive_combine_row() passing in the new row and the
* old row, as demonstrated above. You can call this function for
* NULL rows (it will just return) and for non-interlaced images
* (it just does the memcpy for you) if it will make the code
* easier. Thus, you can just do this for all cases:
*/
png_progressive_combine_row(png_ptr, old_row, new_row);
/* where old_row is what was displayed for previous rows. Note
* that the first pass (pass == 0 really) will completely cover
* the old row, so the rows do not have to be initialized. After
* the first pass (and only for interlaced images), you will have
* to pass the current row as new_row, and the function will combine
* the old row and the new row.
*/
#endif /* READ_INTERLACING */
}
end_callback(png_structp png_ptr, png_infop info)
{
/* This function is called when the whole image has been read,
* including any chunks after the image (up to and including
* the IEND). You will usually have the same info chunk as you
* had in the header, although some data may have been added
* to the comments and time fields.
*
* Most people won't do much here, perhaps setting a flag that
* marks the image as finished.
*/
}
/* Write a png file */
void write_png(char *file_name /* , ... other image information ... */)
{
FILE *fp;
png_structp png_ptr;
png_infop info_ptr;
png_colorp palette;
/* Open the file */
fp = fopen(file_name, "wb");
if (fp == NULL)
return (ERROR);
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
* you can supply NULL for the last three parameters. We also check that
* the library version is compatible with the one used at compile time,
* in case we are using dynamically linked libraries. REQUIRED.
*/
png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
png_voidp user_error_ptr, user_error_fn, user_warning_fn);
if (png_ptr == NULL)
{
fclose(fp);
return (ERROR);
}
/* Allocate/initialize the image information data. REQUIRED */
info_ptr = png_create_info_struct(png_ptr);
if (info_ptr == NULL)
{
fclose(fp);
png_destroy_write_struct(&png_ptr, NULL);
return (ERROR);
}
/* Set error handling. REQUIRED if you aren't supplying your own
* error handling functions in the png_create_write_struct() call.
*/
if (setjmp(png_jmpbuf(png_ptr)))
{
/* If we get here, we had a problem writing the file */
fclose(fp);
png_destroy_write_struct(&png_ptr, &info_ptr);
return (ERROR);
}
/* One of the following I/O initialization functions is REQUIRED */
#ifdef streams /* I/O initialization method 1 */
/* Set up the output control if you are using standard C streams */
png_init_io(png_ptr, fp);
#else no_streams /* I/O initialization method 2 */
/* If you are using replacement write functions, instead of calling
* png_init_io() here you would call
*/
png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
user_IO_flush_function);
/* where user_io_ptr is a structure you want available to the callbacks */
#endif no_streams /* Only use one initialization method */
#ifdef hilevel
/* This is the easy way. Use it if you already have all the
* image info living in the structure. You could "|" many
* PNG_TRANSFORM flags into the png_transforms integer here.
*/
png_write_png(png_ptr, info_ptr, png_transforms, NULL);
#else
/* This is the hard way */
/* Set the image information here. Width and height are up to 2^31,
* bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
( run in 0.517 second using v1.01-cache-2.11-cpan-63c85eba8c4 )