Merge pull request #4568 from ziplantil/ico-append-images

Add append_images support for ICO

Tests/test_file_ico.py

@@ -86,6 +86,20 @@ def test_only_save_relevant_sizes(tmp_path):
         assert im_saved.info["sizes"] == {(16, 16), (24, 24), (32, 32), (48, 48)}
 
 
+def test_save_append_images(tmp_path):
+    # append_images should be used for scaled down versions of the image
+    im = hopper("RGBA")
+    provided_im = Image.new("RGBA", (32, 32), (255, 0, 0))
+    outfile = str(tmp_path / "temp_saved_multi_icon.ico")
+    im.save(outfile, sizes=[(32, 32), (128, 128)], append_images=[provided_im])
+
+    with Image.open(outfile) as reread:
+        assert_image_equal(reread, hopper("RGBA"))
+
+        reread.size = (32, 32)
+        assert_image_equal(reread, provided_im)
+
+
 def test_unexpected_size():
     # This image has been manually hexedited to state that it is 16x32
     # while the image within is still 16x16

docs/handbook/image-file-formats.rst

@@ -127,8 +127,8 @@ following options are available::
     images in the list can be single or multiframe images.
     This is currently supported for GIF, PDF, PNG, TIFF, and WebP.
 
-    It is also supported for ICNS. If images are passed in of relevant sizes,
-    they will be used instead of scaling down the main image.
+    It is also supported for ICO and ICNS. If images are passed in of relevant
+    sizes, they will be used instead of scaling down the main image.
 
 **include_color_table**
     Whether or not to include local color table.
@@ -238,6 +238,15 @@ The :py:meth:`~PIL.Image.Image.save` method supports the following options:
     (64, 64), (128, 128), (256, 256)]``. Any sizes bigger than the original
     size or 256 will be ignored.
 
+The :py:meth:`~PIL.Image.Image.save` method can take the following keyword arguments:
+
+**append_images**
+    A list of images to replace the scaled down versions of the image.
+    The order of the images does not matter, as their use is determined by
+    the size of each image.
+
+    .. versionadded:: 8.1.0
+
 IM
 ^^
 

src/PIL/IcoImagePlugin.py

@@ -54,6 +54,7 @@ def _save(im, fp, filename):
     sizes = list(sizes)
     fp.write(struct.pack("<H", len(sizes)))  # idCount(2)
     offset = fp.tell() + len(sizes) * 16
+    provided_images = {im.size: im for im in im.encoderinfo.get("append_images", [])}
     for size in sizes:
         width, height = size
         # 0 means 256
@@ -65,9 +66,11 @@ def _save(im, fp, filename):
         fp.write(struct.pack("<H", 32))  # wBitCount(2)
 
         image_io = BytesIO()
-        # TODO: invent a more convenient method for proportional scalings
-        tmp = im.copy()
-        tmp.thumbnail(size, Image.LANCZOS, reducing_gap=None)
+        tmp = provided_images.get(size)
+        if not tmp:
+            # TODO: invent a more convenient method for proportional scalings
+            tmp = im.copy()
+            tmp.thumbnail(size, Image.LANCZOS, reducing_gap=None)
         tmp.save(image_io, "png")
         image_io.seek(0)
         image_bytes = image_io.read()