image spec as :mask property for the image

image spec as :mask property for the image

[Evgeny Zajcev]

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Hello,

I've implemented nice feature making possible to use image spec as :mask
property for the image.  This allows making simple image/mask composition
in Emacs.

I need this feature to implement avatars in circles for
https://github.com/zevlg/telega.el/ project directly in Emacs without
executing external programs.

I have done it only for X Window System, I have no experience with coding
for Windows.  Any help to implement it for Windows as well is very helpful

What do think about the feature?

See the patch in the attachment or on github -
https://github.com/zevlg/emacs/commit/c856324968e6f4955b1206e774abfdf36adc61f5

Thanks

PS: Please CC me, I'm not in list

-- 
lg

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diff --git a/src/image.c b/src/image.c
index 992b225..44659a6 100644
--- a/src/image.c
+++ b/src/image.c
@@ -536,6 +536,8 @@ static void x_laplace (struct frame *, struct image *);
 static void x_emboss (struct frame *, struct image *);
 static void x_build_heuristic_mask (struct frame *, struct image *,
                                     Lisp_Object);
+static void x_copy_image_mask (struct frame *, struct image *,
+                               Lisp_Object);
 #ifdef WINDOWSNT
 #define CACHE_IMAGE_TYPE(type, status) \
   do { Vlibrary_cache = Fcons (Fcons (type, status), Vlibrary_cache); } while (0)
@@ -1671,6 +1673,8 @@ postprocess_image (struct frame *f, struct image *img)
 	 `:mask (heuristic (R G B))'
 	 means build a mask from color (R G B) in the
 	 image.
+	 `:mask image-spec'
+	 means use mask from another image, their sizes
 	 `:mask nil'
 	 means remove a mask, if any.  */
 
@@ -1693,6 +1697,10 @@ postprocess_image (struct frame *f, struct image *img)
 	      else
 		x_build_heuristic_mask (f, img, XCDR (mask));
 	    }
+	  else if (valid_image_p (mask))
+	    {
+	      x_copy_image_mask (f, img, mask);
+	    }
 	  else if (NILP (mask) && found_p && img->mask)
 	    x_clear_image_1 (f, img, CLEAR_IMAGE_MASK);
 	}
@@ -5158,6 +5166,60 @@ x_build_heuristic_mask (struct frame *f, struct image *img, Lisp_Object how)
   image_unget_x_image_or_dc (img, 0, ximg, prev);
 }
 
+/* Copy mask from image specified by MASK_SPEC.
+
+   Image specified by MASK_SPEC should have mask, and both
+   images should match in size */
+
+static void
+x_copy_image_mask (struct frame *f, struct image *img, Lisp_Object mask_spec)
+{
+  ptrdiff_t mask_id;
+  struct image *mask;
+  int x, y;
+  XImagePtr mask_ximg;
+  XImagePtr src_mask_ximg;
+
+  eassert (valid_image_p (mask_spec));
+  mask_id = lookup_image (f, mask_spec);
+  mask = IMAGE_FROM_ID (f, mask_id);
+
+  if (! mask->mask)
+    {
+      image_error (":mask spec should be masked image `%s'", mask->spec);
+      return;
+    }
+
+  if (img->width != mask->width || img->height != mask->height)
+    {
+      image_error ("Image `%s' and its :mask `%s' does not match in size",
+		   img->spec, mask->spec);
+      return;
+    }
+
+  if (img->mask)
+    x_clear_image_1 (f, img, CLEAR_IMAGE_MASK);
+
+  /* Create an image and pixmap serving as mask.  */
+  if (! image_create_x_image_and_pixmap (f, img, img->width, img->height, 1,
+					 &mask_ximg, 1))
+    return;
+
+  src_mask_ximg = image_get_x_image (f, mask, 1);
+
+  for (y = 0; y < img->height; ++y)
+    for (x = 0; x < img->width; ++x)
+      XPutPixel (mask_ximg, x, y, XGetPixel (src_mask_ximg, x, y));
+
+  image_unget_x_image (mask, 1, src_mask_ximg);
+
+  /* Fill in the background_transparent field while we have the mask handy. */
+  image_background_transparent (img, f, mask_ximg);
+
+  /* Finally put mask_ximg into the image.  */
+  image_put_x_image (f, img, mask_ximg, 1);
+}
+
 \f
 /***********************************************************************
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