mewin/libpng
1
0
Fork 0
mirror of https://git.code.sf.net/p/libpng/code.git synced 2025-07-10 18:04:09 +02:00
Code Issues Projects Releases Wiki Activity

Imported from libpng-0.97c.tar

Browse Source
This commit is contained in:
Glenn Randers-Pehrson
1998-01-07 20:54:20 -06:00
parent 70e3f543f1
commit 2687fcc7b5
22 changed files with 259 additions and 218 deletions
Download Patch File Download Diff File Expand all files Collapse all files

88
pngrtran.c
View File

@@ -1,11 +1,12 @@
/* pngrtran.c - transforms the data in a row for PNG readers
*
* libpng 1.00.97
* libpng 0.97
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* May 28, 1997
* Copyright (c) 1998, Glenn Randers-Pehrson
* January 7, 1998
*
* This file contains functions optionally called by an application
* in order to tell libpng how to handle data when reading a PNG.
@@ -21,35 +22,40 @@
* many machines. However, it does take more operations than the corresponding
* divide method, so it may be slower on some RISC systems. There are two
* shifts (by 8 or 16 bits) and an addition, versus a single integer divide.
* The results may also be off by one for certain values.
*
* Note that the rounding factors are NOT supposed to be the same! 128 and
* 32768 are correct for the NODIV code; 127 and 32767 are correct for the
* standard method.
*
* [Optimized code by Greg Roelofs and Mark Adler...blame us for bugs. :-) ]
*/
/* pixel and background should be in gamma 1.0 space */
#define png_composite(composite, pixel, trans, background) \
{ png_uint_16 temp = ((png_uint_16)(pixel) * (png_uint_16)(trans) + \
(png_uint_16)(background)*(png_uint_16)(255 - \
(png_uint_16)(trans)) + (png_uint_16)127); \
(composite) = (png_byte)(((temp >> 8) + temp) >> 8); }
/* fg and bg should be in `gamma 1.0' space; alpha is the opacity */
# define png_composite(composite, fg, alpha, bg) \
{ png_uint_16 temp = ((png_uint_16)(fg) * (png_uint_16)(alpha) + \
(png_uint_16)(bg)*(png_uint_16)(255 - \
(png_uint_16)(alpha)) + (png_uint_16)128); \
(composite) = (png_byte)((temp + (temp >> 8)) >> 8); }
# define png_composite_16(composite, fg, alpha, bg) \
{ png_uint_32 temp = ((png_uint_32)(fg) * (png_uint_32)(alpha) + \
(png_uint_32)(bg)*(png_uint_32)(65535L - \
(png_uint_32)(alpha)) + (png_uint_32)32768L); \
(composite) = (png_uint_16)((temp + (temp >> 16)) >> 16); }
#else /* standard method using integer division */
/* fg and bg should be in `gamma 1.0' space; alpha is the opacity */
# define png_composite(composite, fg, alpha, bg) \
(composite) = (png_byte)(((png_uint_16)(fg) * (png_uint_16)(alpha) + \
(png_uint_16)(bg) * (png_uint_16)(255 - (png_uint_16)(alpha)) + \
(png_uint_16)127) / 255)
# define png_composite_16(composite, fg, alpha, bg) \
(composite) = (png_uint_16)(((png_uint_32)(fg) * (png_uint_32)(alpha) + \
(png_uint_32)(bg)*(png_uint_32)(65535L - (png_uint_32)(alpha)) + \
(png_uint_32)32767) / (png_uint_32)65535L)
#endif /* ?PNG_READ_COMPOSITE_NODIV_SUPPORTED */
/* pixel and background should be in gamma 1.0 space */
#define png_composite_16(composite, pixel, trans, background) \
{ png_uint_32 temp = ((png_uint_32)(pixel) * (png_uint_32)(trans) + \
(png_uint_32)(background)*(png_uint_32)(65535L - \
(png_uint_32)(trans)) + (png_uint_32)32767); \
(composite) = (png_uint_16)(((temp >> 16) + temp) >> 16); }
#else
/* pixel and background should be in gamma 1.0 space */
#define png_composite(composite, pixel, trans, background) \
(composite) = (png_byte)(((png_uint_16)(pixel) * (png_uint_16)(trans) + \
(png_uint_16)(background) * (png_uint_16)(255 - (png_uint_16)(trans)) + \
(png_uint_16)127) / 255)
/* pixel and background should be in gamma 1.0 space */
#define png_composite_16(composite, pixel, trans, background) \
(composite) = (png_uint_16)(((png_uint_32)(pixel) * (png_uint_32)(trans) + \
(png_uint_32)(background)*(png_uint_32)(65535L - (png_uint_32)(trans)) + \
(png_uint_32)32767) / (png_uint_32)65535L)
#endif
/* Set the action on getting a CRC error for an ancillary or critical chunk. */
void
@@ -1344,6 +1350,16 @@ png_do_chop(png_row_infop row_info, png_bytep row)
*dp = (((((png_uint_32)(*sp) << 8) |
(png_uint_32)(*(sp + 1))) * 255 + 127) / (png_uint_32)65535L;
* GRR: no, I think this is what it really should be:
*dp = (((((png_uint_32)(*sp) << 8) |
(png_uint_32)(*(sp + 1))) + 128L) / (png_uint_32)257L;
* GRR: here's the exact calculation with shifts:
temp = (((png_uint_32)(*sp) << 8) | (png_uint_32)(*(sp + 1))) + 128L;
*dp = (temp - (temp >> 8)) >> 8;
* Approximate calculation with shift/add instead of multiply/divide:
*dp = ((((png_uint_32)(*sp) << 8) |
(png_uint_32)((int)(*(sp + 1)) - *sp)) + 128) >> 8;
@@ -2558,6 +2574,22 @@ png_do_gamma(png_row_infop row_info, png_bytep row,
}
case PNG_COLOR_TYPE_GRAY:
{
if (row_info->bit_depth == 2)
{
for (i = 0, sp = row; i < row_info->width; i += 4)
{
int a = *sp & 0xc0;
int b = *sp & 0x30;
int c = *sp & 0x0c;
int d = *sp & 0x03;
*sp = ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)]) ) & 0xc0)|
((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) );
sp++;
}
}
if (row_info->bit_depth == 4)
{
for (i = 0, sp = row; i < row_info->width; i += 2)