From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 21 May 2014 19:51:58 +0000 (-0700)
Subject: Don't assume that ImageMagick uses a 16-bit quantum.
X-Git-Tag: emacs-25.0.90~2640^2~74
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=6c596cb2ea3075afab8812f45803683be2949323;p=emacs.git

Don't assume that ImageMagick uses a 16-bit quantum.

* image.c (imagemagick_load_image): Port to hosts that do not use
a 16-bit quantum, i.e., QuantumRange does not equal 65535.

Fixes: debbugs:17519
---

diff --git a/src/ChangeLog b/src/ChangeLog
index d6e21a777c2..29039395374 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2014-05-21  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Don't assume that ImageMagick uses a 16-bit quantum (Bug#17519).
+	* image.c (imagemagick_load_image): Port to hosts that do not use
+	a 16-bit quantum, i.e., QuantumRange does not equal 65535.
+
 2014-05-21  Leo Liu  <sdl.web@gmail.com>
 
 	* fns.c (Fnreverse): Accept strings for SEQ and update doc-string.
diff --git a/src/image.c b/src/image.c
index 047f7517501..f7c3ef52563 100644
--- a/src/image.c
+++ b/src/image.c
@@ -8368,6 +8368,7 @@ imagemagick_load_image (struct frame *f, struct image *img,
 #endif /* HAVE_MAGICKEXPORTIMAGEPIXELS */
     {
       size_t image_height;
+      double color_scale = 65535.0 / QuantumRange;
 
       /* Try to create a x pixmap to hold the imagemagick pixmap.  */
       if (!image_create_x_image_and_pixmap (f, img, width, height, 0,
@@ -8408,9 +8409,9 @@ imagemagick_load_image (struct frame *f, struct image *img,
               PixelGetMagickColor (pixels[x], &pixel);
               XPutPixel (ximg, x, y,
                          lookup_rgb_color (f,
-                                           pixel.red,
-                                           pixel.green,
-                                           pixel.blue));
+					   color_scale * pixel.red,
+					   color_scale * pixel.green,
+					   color_scale * pixel.blue));
             }
         }
       DestroyPixelIterator (iterator);