From: Chong Yidong <cyd@stupidchicken.com>
Date: Fri, 9 May 2008 02:37:31 +0000 (+0000)
Subject: (png_load): Use correct bit-depth for setting background color.
X-Git-Tag: emacs-pretest-23.0.90~5694
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=c4f13f44fbeb917916f71ac0fa9e7a100ed8b643;p=emacs.git

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

diff --git a/src/image.c b/src/image.c
index 48b223c6c76..3a972197293 100644
--- a/src/image.c
+++ b/src/image.c
@@ -6542,7 +6542,6 @@ 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.  */
@@ -6684,27 +6683,6 @@ 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.  */
@@ -6713,6 +6691,7 @@ 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.  */
@@ -6724,27 +6703,18 @@ 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;
@@ -6753,9 +6723,9 @@ 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