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src/Source/LibPNG/pngpriv.h  view on Meta::CPAN

 */
#define PNG_DIV65535(v24) (((v24) + 32895) >> 16)
#define PNG_DIV257(v16) PNG_DIV65535((png_uint_32)(v16) * 255)

/* Added to libpng-1.2.6 JB */
#define PNG_ROWBYTES(pixel_bits, width) \
    ((pixel_bits) >= 8 ? \
    ((png_size_t)(width) * (((png_size_t)(pixel_bits)) >> 3)) : \
    (( ((png_size_t)(width) * ((png_size_t)(pixel_bits))) + 7) >> 3) )

/* PNG_OUT_OF_RANGE returns true if value is outside the range
 * ideal-delta..ideal+delta.  Each argument is evaluated twice.
 * "ideal" and "delta" should be constants, normally simple
 * integers, "value" a variable. Added to libpng-1.2.6 JB
 */
#define PNG_OUT_OF_RANGE(value, ideal, delta) \
   ( (value) < (ideal)-(delta) || (value) > (ideal)+(delta) )

/* Conversions between fixed and floating point, only defined if
 * required (to make sure the code doesn't accidentally use float
 * when it is supposedly disabled.)
 */
#ifdef PNG_FLOATING_POINT_SUPPORTED
/* The floating point conversion can't overflow, though it can and
 * does lose accuracy relative to the original fixed point value.
 * In practice this doesn't matter because png_fixed_point only
 * stores numbers with very low precision.  The png_ptr and s
 * arguments are unused by default but are there in case error
 * checking becomes a requirement.
 */
#define png_float(png_ptr, fixed, s) (.00001 * (fixed))

/* The fixed point conversion performs range checking and evaluates
 * its argument multiple times, so must be used with care.  The
 * range checking uses the PNG specification values for a signed
 * 32 bit fixed point value except that the values are deliberately
 * rounded-to-zero to an integral value - 21474 (21474.83 is roughly
 * (2^31-1) * 100000). 's' is a string that describes the value being
 * converted.
 *
 * NOTE: this macro will raise a png_error if the range check fails,
 * therefore it is normally only appropriate to use this on values
 * that come from API calls or other sources where an out of range
 * error indicates a programming error, not a data error!
 *
 * NOTE: by default this is off - the macro is not used - because the
 * function call saves a lot of code.
 */
#ifdef PNG_FIXED_POINT_MACRO_SUPPORTED
#define png_fixed(png_ptr, fp, s) ((fp) <= 21474 && (fp) >= -21474 ?\
    ((png_fixed_point)(100000 * (fp))) : (png_fixed_error(png_ptr, s),0))
#endif
/* else the corresponding function is defined below, inside the scope of the
 * cplusplus test.
 */
#endif

/* Constants for known chunk types.  If you need to add a chunk, define the name
 * here.  For historical reasons these constants have the form png_<name>; i.e.
 * the prefix is lower case.  Please use decimal values as the parameters to
 * match the ISO PNG specification and to avoid relying on the C locale
 * interpretation of character values.
 *
 * Prior to 1.5.6 these constants were strings, as of 1.5.6 png_uint_32 values
 * are computed and a new macro (PNG_STRING_FROM_CHUNK) added to allow a string
 * to be generated if required.
 *
 * PNG_32b correctly produces a value shifted by up to 24 bits, even on
 * architectures where (int) is only 16 bits.
 */
#define PNG_32b(b,s) ((png_uint_32)(b) << (s))
#define PNG_U32(b1,b2,b3,b4) \
   (PNG_32b(b1,24) | PNG_32b(b2,16) | PNG_32b(b3,8) | PNG_32b(b4,0))

/* Constants for known chunk types.
 *
 * MAINTAINERS: If you need to add a chunk, define the name here.
 * For historical reasons these constants have the form png_<name>; i.e.
 * the prefix is lower case.  Please use decimal values as the parameters to
 * match the ISO PNG specification and to avoid relying on the C locale
 * interpretation of character values.  Please keep the list sorted.
 *
 * Notice that PNG_U32 is used to define a 32-bit value for the 4 byte chunk
 * type.  In fact the specification does not express chunk types this way,
 * however using a 32-bit value means that the chunk type can be read from the
 * stream using exactly the same code as used for a 32-bit unsigned value and
 * can be examined far more efficiently (using one arithmetic compare).
 *
 * Prior to 1.5.6 the chunk type constants were expressed as C strings.  The
 * libpng API still uses strings for 'unknown' chunks and a macro,
 * PNG_STRING_FROM_CHUNK, allows a string to be generated if required.  Notice
 * that for portable code numeric values must still be used; the string "IHDR"
 * is not portable and neither is PNG_U32('I', 'H', 'D', 'R').
 *
 * In 1.7.0 the definitions will be made public in png.h to avoid having to
 * duplicate the same definitions in application code.
 */
#define png_IDAT PNG_U32( 73,  68,  65,  84)
#define png_IEND PNG_U32( 73,  69,  78,  68)
#define png_IHDR PNG_U32( 73,  72,  68,  82)
#define png_PLTE PNG_U32( 80,  76,  84,  69)
#define png_bKGD PNG_U32( 98,  75,  71,  68)
#define png_cHRM PNG_U32( 99,  72,  82,  77)
#define png_fRAc PNG_U32(102,  82,  65,  99) /* registered, not defined */
#define png_gAMA PNG_U32(103,  65,  77,  65)
#define png_gIFg PNG_U32(103,  73,  70, 103)
#define png_gIFt PNG_U32(103,  73,  70, 116) /* deprecated */
#define png_gIFx PNG_U32(103,  73,  70, 120)
#define png_hIST PNG_U32(104,  73,  83,  84)
#define png_iCCP PNG_U32(105,  67,  67,  80)
#define png_iTXt PNG_U32(105,  84,  88, 116)
#define png_oFFs PNG_U32(111,  70,  70, 115)
#define png_pCAL PNG_U32(112,  67,  65,  76)
#define png_pHYs PNG_U32(112,  72,  89, 115)
#define png_sBIT PNG_U32(115,  66,  73,  84)
#define png_sCAL PNG_U32(115,  67,  65,  76)
#define png_sPLT PNG_U32(115,  80,  76,  84)
#define png_sRGB PNG_U32(115,  82,  71,  66)
#define png_sTER PNG_U32(115,  84,  69,  82)
#define png_tEXt PNG_U32(116,  69,  88, 116)
#define png_tIME PNG_U32(116,  73,  77,  69)
#define png_tRNS PNG_U32(116,  82,  78,  83)
#define png_zTXt PNG_U32(122,  84,  88, 116)

/* The following will work on (signed char*) strings, whereas the get_uint_32
 * macro will fail on top-bit-set values because of the sign extension.
 */
#define PNG_CHUNK_FROM_STRING(s)\
   PNG_U32(0xff&(s)[0], 0xff&(s)[1], 0xff&(s)[2], 0xff&(s)[3])

/* This uses (char), not (png_byte) to avoid warnings on systems where (char) is
 * signed and the argument is a (char[])  This macro will fail miserably on
 * systems where (char) is more than 8 bits.
 */
#define PNG_STRING_FROM_CHUNK(s,c)\
   (void)(((char*)(s))[0]=(char)((c)>>24), ((char*)(s))[1]=(char)((c)>>16),\
   ((char*)(s))[2]=(char)((c)>>8), ((char*)(s))[3]=(char)((c)))

/* Do the same but terminate with a null character. */
#define PNG_CSTRING_FROM_CHUNK(s,c)\