Support transparency for ImageMagick images.

* src/image.c (imagemagick_load_image): Implement transparency.

* doc/lispref/display.texi (ImageMagick Images): ImageMagick now supports the
:background property.

2 files changed, 61 insertions, 56 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 919dcc10098..1aba1913f46 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2012-06-11  Chong Yidong  <cyd@gnu.org>
+
+        * image.c (imagemagick_load_image): Implement transparency.
+
 2012-06-10  Andreas Schwab  <schwab@linux-m68k.org>
 
         * regex.c (at_begline_loc_p): Also recognize `(?N:' and correctly
diff --git a/src/image.c b/src/image.c
index b6cdb6c8290..15fd7bbeab7 100644
--- a/src/image.c
+++ b/src/image.c
@@ -7599,19 +7599,14 @@ imagemagick_load_image (struct frame *f, struct image *img,
                         unsigned char *contents, unsigned int size,
                         char *filename)
 {
-  size_t width;
-  size_t height;
-
+  size_t width, height;
   MagickBooleanType status;
-
   XImagePtr ximg;
-  int x;
-  int y;
-
-  MagickWand  *image_wand;
-  MagickWand  *ping_wand;
+  int x, y;
+  MagickWand *image_wand;
+  MagickWand *ping_wand;
   PixelIterator *iterator;
-  PixelWand  **pixels;
+  PixelWand **pixels, *bg_wand = NULL;
   MagickPixelPacket  pixel;
   Lisp_Object image;
   Lisp_Object value;
@@ -7620,10 +7615,6 @@ imagemagick_load_image (struct frame *f, struct image *img,
   int desired_width, desired_height;
   double rotation;
   int pixelwidth;
-  ImageInfo  *image_info;
-  ExceptionInfo *exception;
-  Image * im_image;
-
 
   /* Handle image index for image types who can contain more than one image.
      Interface :index is same as for GIF.  First we "ping" the image to see how
@@ -7637,14 +7628,9 @@ imagemagick_load_image (struct frame *f, struct image *img,
   ping_wand = NewMagickWand ();
   /* MagickSetResolution (ping_wand, 2, 2);   (Bug#10112)  */
 
-  if (filename != NULL)
-    {
-      status = MagickPingImage (ping_wand, filename);
-    }
-  else
-    {
-      status = MagickPingImageBlob (ping_wand, contents, size);
-    }
+  status = filename
+    ? MagickPingImage (ping_wand, filename)
+    : MagickPingImageBlob (ping_wand, contents, size);
 
   if (status == MagickFalse)
     {
@@ -7653,7 +7639,7 @@ imagemagick_load_image (struct frame *f, struct image *img,
       return 0;
     }
 
-  if (! (0 <= ino && ino < MagickGetNumberImages (ping_wand)))
+  if (ino < 0 || ino >= MagickGetNumberImages (ping_wand))
     {
       image_error ("Invalid image number `%s' in image `%s'",
                    image, img->spec);
@@ -7670,39 +7656,46 @@ imagemagick_load_image (struct frame *f, struct image *img,
   DestroyMagickWand (ping_wand);
 
   /* Now we know how many images are inside the file.  If it's not a
-     bundle, the number is one.  */
-
-  if (filename != NULL)
-    {
-      image_info = CloneImageInfo ((ImageInfo *) NULL);
-      (void) strcpy (image_info->filename, filename);
-      image_info->number_scenes = 1;
-      image_info->scene = ino;
-      exception = AcquireExceptionInfo ();
+     bundle, the number is one.  Load the image data.  */
 
-      im_image = ReadImage (image_info, exception);
-      DestroyExceptionInfo (exception);
+  image_wand = NewMagickWand ();
 
-      if (im_image == NULL)
-        goto imagemagick_no_wand;
-      image_wand = NewMagickWandFromImage (im_image);
-      DestroyImage (im_image);
-    }
-  else
+  if ((filename
+       ? MagickReadImage (image_wand, filename)
+       : MagickReadImageBlob (image_wand, contents, size))
+      == MagickFalse)
     {
-      image_wand = NewMagickWand ();
-      if (MagickReadImageBlob (image_wand, contents, size) == MagickFalse)
-        {
-          imagemagick_error (image_wand);
-          goto imagemagick_error;
-        }
+      imagemagick_error (image_wand);
+      goto imagemagick_error;
     }
 
+  /* Retrieve the frame's background color, for use later.  */
+  {
+    XColor bgcolor;
+    Lisp_Object specified_bg;
+
+    specified_bg = image_spec_value (img->spec, QCbackground, NULL);
+    if (!STRINGP (specified_bg)
+        || !x_defined_color (f, SSDATA (specified_bg), &bgcolor, 0))
+      {
+#ifndef HAVE_NS
+        bgcolor.pixel = FRAME_BACKGROUND_PIXEL (f);
+        x_query_color (f, &bgcolor);
+#else
+        ns_query_color (FRAME_BACKGROUND_COLOR (f), &bgcolor, 1);
+#endif
+      }
+
+    bg_wand = NewPixelWand ();
+    PixelSetRed   (bg_wand, (double) bgcolor.red   / 65535);
+    PixelSetGreen (bg_wand, (double) bgcolor.green / 65535);
+    PixelSetBlue  (bg_wand, (double) bgcolor.blue  / 65535);
+  }
+
   /* If width and/or height is set in the display spec assume we want
      to scale to those values.  If either h or w is unspecified, the
      unspecified should be calculated from the specified to preserve
      aspect ratio.  */
-
   value = image_spec_value (img->spec, QCwidth, NULL);
   desired_width = (INTEGERP (value)  ? XFASTINT (value) : -1);
   value = image_spec_value (img->spec, QCheight, NULL);
@@ -7768,13 +7761,8 @@ imagemagick_load_image (struct frame *f, struct image *img,
   value = image_spec_value (img->spec, QCrotation, NULL);
   if (FLOATP (value))
     {
-      PixelWand* background = NewPixelWand ();
-      PixelSetColor (background, "#ffffff");/*TODO remove hardcode*/
-
       rotation = extract_float (value);
-
-      status = MagickRotateImage (image_wand, background, rotation);
-      DestroyPixelWand (background);
+      status = MagickRotateImage (image_wand, bg_wand, rotation);
       if (status == MagickFalse)
         {
           image_error ("Imagemagick image rotate failed", Qnil, Qnil);
@@ -7788,6 +7776,18 @@ imagemagick_load_image (struct frame *f, struct image *img,
   height = MagickGetImageHeight (image_wand);
   width = MagickGetImageWidth (image_wand);
 
+  /* Set the canvas background color to the frame or specified
+     background, and flatten the image.  Note: as of ImageMagick
+     6.6.0, SVG image transparency is not handled properly
+     (e.g. etc/images/splash.svg shows a white background always).  */
+  {
+    MagickWand *new_wand;
+    MagickSetImageBackgroundColor (image_wand, bg_wand);
+    new_wand = MagickMergeImageLayers (image_wand, MergeLayer);
+    DestroyMagickWand (image_wand);
+    image_wand = new_wand;
+  }
+
   if (! (width <= INT_MAX && height <= INT_MAX
          && check_image_size (f, width, height)))
     {
@@ -7895,7 +7895,6 @@ imagemagick_load_image (struct frame *f, struct image *img,
                                width, height,
                                exportdepth,
                                pixelwidth,
-                               /*&(img->pixmap));*/
                                ximg->data);
 #else
       image_error ("You don't have MagickExportImagePixels, upgrade ImageMagick!",
@@ -7910,7 +7909,6 @@ imagemagick_load_image (struct frame *f, struct image *img,
   free_color_table ();
 #endif /* COLOR_TABLE_SUPPORT */
 
-
   img->width  = width;
   img->height = height;
 
@@ -7919,9 +7917,10 @@ imagemagick_load_image (struct frame *f, struct image *img,
   x_put_x_image (f, ximg, img->pixmap, width, height);
   x_destroy_x_image (ximg);
 
-
   /* Final cleanup. image_wand should be the only resource left. */
   DestroyMagickWand (image_wand);
+  if (bg_wand) DestroyPixelWand (bg_wand);
+
   /* `MagickWandTerminus' terminates the imagemagick environment.  */
   MagickWandTerminus ();
 
@@ -7929,6 +7928,8 @@ imagemagick_load_image (struct frame *f, struct image *img,
 
  imagemagick_error:
   DestroyMagickWand (image_wand);
+  if (bg_wand) DestroyPixelWand (bg_wand);
+
  imagemagick_no_wand:
   MagickWandTerminus ();
   /* TODO more cleanup.  */