(png_load): Use correct bit-depth for setting background color.

2 files changed, 14 insertions, 39 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d7826d013aa..0a9f3ec9a67 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2008-07-07  Chong Yidong  <cyd@stupidchicken.com>
+
+        * image.c (png_load): Use correct bit-depth for setting background
+        color.
+
 2008-05-15  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
 
         * macterm.c (x_draw_relief_rect): Remove unused variable `dpy'.
diff --git a/src/image.c b/src/image.c
index 9981b21365a..f2dc1ae30ca 100644
--- a/src/image.c
+++ b/src/image.c
@@ -6517,7 +6517,6 @@ png_load (f, img)
   png_byte channels;
   png_uint_32 row_bytes;
   int transparent_p;
-  double screen_gamma;
   struct png_memory_storage tbr;  /* Data to be read */
 
   /* Find out what file to load.  */
@@ -6659,27 +6658,6 @@ png_load (f, img)
       || color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
     fn_png_set_gray_to_rgb (png_ptr);
 
-  screen_gamma = (f->gamma ? 1 / f->gamma / 0.45455 : 2.2);
-
-#if 0 /* Avoid double gamma correction for PNG images. */
-  { /* Tell the PNG lib to handle gamma correction for us.  */
-    int intent;
-    double image_gamma;
-#if defined(PNG_READ_sRGB_SUPPORTED) || defined(PNG_WRITE_sRGB_SUPPORTED)
-    if (png_get_sRGB (png_ptr, info_ptr, &intent))
-      /* The libpng documentation says this is right in this case.  */
-      png_set_gamma (png_ptr, screen_gamma, 0.45455);
-    else
-#endif
-      if (png_get_gAMA (png_ptr, info_ptr, &image_gamma))
-        /* Image contains gamma information.  */
-        png_set_gamma (png_ptr, screen_gamma, image_gamma);
-      else
-        /* Use the standard default for the image gamma.  */
-        png_set_gamma (png_ptr, screen_gamma, 0.45455);
-  }
-#endif /* if 0 */
-
   /* Handle alpha channel by combining the image with a background
      color.  Do this only if a real alpha channel is supplied.  For
      simple transparency, we prefer a clipping mask.  */
@@ -6688,6 +6666,7 @@ png_load (f, img)
       png_color_16 *image_bg;
       Lisp_Object specified_bg
         = image_spec_value (img->spec, QCbackground, NULL);
+      int shift = (bit_depth == 16) ? 0 : 8;
 
       if (STRINGP (specified_bg))
         /* The user specified `:background', use that.  */
@@ -6699,27 +6678,18 @@ png_load (f, img)
               png_color_16 user_bg;
 
               bzero (&user_bg, sizeof user_bg);
-              user_bg.red = color.red >> 8;
-              user_bg.green = color.green >> 8;
-              user_bg.blue = color.blue >> 8;
+              user_bg.red = color.red >> shift;
+              user_bg.green = color.green >> shift;
+              user_bg.blue = color.blue >> shift;
 
               fn_png_set_background (png_ptr, &user_bg,
                                      PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
             }
         }
-      /* The commented-out code checked if the png specifies a default
-         background color, and uses that.  Since we use the current
-         frame background, it is OK for us to ignore this.
-
-      else if (fn_png_get_bKGD (png_ptr, info_ptr, &image_bg))
-        fn_png_set_background (png_ptr, image_bg,
-                               PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
-        */
       else
         {
-          /* Image does not contain a background color with which
-             to combine the image data via an alpha channel.  Use
-             the frame's background instead.  */
+          /* We use the current frame background, ignoring any default
+             background color set by the image.  */
 #ifdef HAVE_X_WINDOWS
           XColor color;
           png_color_16 frame_background;
@@ -6728,9 +6698,9 @@ png_load (f, img)
           x_query_color (f, &color);
 
           bzero (&frame_background, sizeof frame_background);
-          frame_background.red = color.red >> 8;
-          frame_background.green = color.green >> 8;
-          frame_background.blue = color.blue >> 8;
+          frame_background.red = color.red >> shift;
+          frame_background.green = color.green >> shift;
+          frame_background.blue = color.blue >> shift;
 #endif /* HAVE_X_WINDOWS */
 
 #ifdef HAVE_NTGUI