Imported from libpng-1.2.2beta2.tar
diff --git a/pngrtran.c b/pngrtran.c
index 8f846c9..94216b2 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,9 +1,9 @@
/* pngrtran.c - transforms the data in a row for PNG readers
*
- * libpng 1.2.2beta1 - February 22, 2002
+ * libpng 1.2.2beta2 - February 24, 2002
* For conditions of distribution and use, see copyright notice in png.h
- * Copyright (c) 1998-2001 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
*
@@ -510,13 +510,19 @@
* only do transformations on images where the file_gamma and screen_gamma
* are not close reciprocals, otherwise it slows things down slightly, and
* also needlessly introduces small errors.
+ *
+ * We will turn off gamma transformation later if no semitransparent entries
+ * are present in the tRNS array for palette images. We can't do it here
+ * because we don't necessarily have the tRNS chunk yet.
*/
void PNGAPI
png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
{
png_debug(1, "in png_set_gamma\n");
- if (fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD)
- png_ptr->transformations |= PNG_GAMMA;
+ if ((fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD) ||
+ (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
+ (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+ png_ptr->transformations |= PNG_GAMMA;
png_ptr->gamma = (float)file_gamma;
png_ptr->screen_gamma = (float)scrn_gamma;
}
@@ -746,6 +752,22 @@
png_ptr->background_1 = png_ptr->background;
#endif
#if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
+
+ if ((color_type == PNG_COLOR_TYPE_PALETTE && png_ptr->num_trans != 0)
+ && (fabs(png_ptr->screen_gamma * png_ptr->gamma - 1.0)
+ < PNG_GAMMA_THRESHOLD))
+ {
+ int i,k;
+ k=0;
+ for (i=0; i<png_ptr->num_trans; i++)
+ {
+ if (png_ptr->trans[i] != 0 && png_ptr->trans[i] != 0xff)
+ k=1; /* partial transparency is present */
+ }
+ if (k == 0)
+ png_ptr->transformations &= (~PNG_GAMMA);
+ }
+
if (png_ptr->transformations & (PNG_GAMMA | PNG_RGB_TO_GRAY))
{
png_build_gamma_table(png_ptr);
@@ -754,6 +776,8 @@
{
if (color_type == PNG_COLOR_TYPE_PALETTE)
{
+ /* could skip if no transparency and
+ */
png_color back, back_1;
png_colorp palette = png_ptr->palette;
int num_palette = png_ptr->num_palette;
@@ -3150,17 +3174,17 @@
png_uint_16 v, w, x;
v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
- png_composite_16(w, v, a, background->red);
+ png_composite_16(w, v, a, background_1->red);
x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
*dp = (png_byte)((x >> 8) & 0xff);
*(dp + 1) = (png_byte)(x & 0xff);
v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
- png_composite_16(w, v, a, background->green);
+ png_composite_16(w, v, a, background_1->green);
x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
*(dp + 2) = (png_byte)((x >> 8) & 0xff);
*(dp + 3) = (png_byte)(x & 0xff);
v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
- png_composite_16(w, v, a, background->blue);
+ png_composite_16(w, v, a, background_1->blue);
x = gamma_16_from_1[(w & 0xff) >> gamma_shift][w >> 8];
*(dp + 4) = (png_byte)((x >> 8) & 0xff);
*(dp + 5) = (png_byte)(x & 0xff);
