Working GbrImagePlugin for version 2 GBR (gimp brush) files

PIL/GbrImagePlugin.py

@@ -1,17 +1,28 @@
 #
 # The Python Imaging Library
-# $Id$
 #
 # load a GIMP brush file
 #
 # History:
 #       96-03-14 fl     Created
+#       16-01-08 es     Version 2
 #
 # Copyright (c) Secret Labs AB 1997.
 # Copyright (c) Fredrik Lundh 1996.
+# Copyright (c) Eric Soroos 2016.
 #
 # See the README file for information on usage and redistribution.
 #
+#
+# See https://github.com/GNOME/gimp/blob/master/devel-docs/gbr.txt for
+# format documentation.
+#
+# This code Interprets version 1 and 2 .gbr files.
+# Version 1 files are obsolete, and should not be used for new
+#   brushes.
+# Version 2 files are saved by GIMP v2.8 (at least)
+# Version 3 files have a format specifier of 18 for 16bit floats in
+#   the color depth field. This is currently unsupported by Pillow.
 
 from PIL import Image, ImageFile, _binary
 
@@ -19,7 +30,7 @@ i32 = _binary.i32be
 
 
 def _accept(prefix):
-    return len(prefix) >= 8 and i32(prefix) >= 20 and i32(prefix[4:8]) == 1
+    return len(prefix) >= 8 and i32(prefix[:4]) >= 20 and i32(prefix[4:8]) in (1,2)
 
 
 ##
@@ -31,41 +42,53 @@ class GbrImageFile(ImageFile.ImageFile):
     format_description = "GIMP brush file"
 
     def _open(self):
-
         header_size = i32(self.fp.read(4))
         version = i32(self.fp.read(4))
-        if header_size < 20 or version != 1:
+        if header_size < 20:
             raise SyntaxError("not a GIMP brush")
+        if version not in (1,2):
+            raise SyntaxError("Unsupported GIMP brush version: %s" %version)
 
         width = i32(self.fp.read(4))
         height = i32(self.fp.read(4))
         color_depth = i32(self.fp.read(4))
-        if width <= 0 or height <= 0 or color_depth != 1:
+        if width <= 0 or height <= 0: 
             raise SyntaxError("not a GIMP brush")
+        if color_depth not in (1,4):
+            raise SyntaxError("Unsupported GMP brush color depth: %s" %color_depth)
+        
+        if version == 1:
+            comment_length = header_size-20
+        else:
+            comment_length = header_size-28
+            magic_number = self.fp.read(4)
+            if magic_number != b'GIMP':
+                raise SyntaxError("not a GIMP brush, bad magic number")
+            self.info['spacing'] = i32(self.fp.read(4))
 
-        comment = self.fp.read(header_size - 20)[:-1]
+        comment = self.fp.read(comment_length)[:-1]
 
-        self.mode = "L"
+        if color_depth == 1:
+            self.mode = "L"
+        else:
+            self.mode = 'RGBA'
+            
         self.size = width, height
 
         self.info["comment"] = comment
 
-        # Since the brush is so small, we read the data immediately
-        self.data = self.fp.read(width * height)
+        # Image might not be small
+        Image._decompression_bomb_check(self.size)
+
+        # Data is an uncompressed block of w * h * bytes/pixel 
+        self._data_size = width * height * color_depth
 
     def load(self):
-
-        if not self.data:
-            return
-
-        # create an image out of the brush data block
         self.im = Image.core.new(self.mode, self.size)
-        self.im.frombytes(self.data)
-        self.data = b""
+        self.frombytes(self.fp.read(self._data_size))
 
 #
 # registry
 
 Image.register_open(GbrImageFile.format, GbrImageFile, _accept)
-
 Image.register_extension(GbrImageFile.format, ".gbr")

Tests/test_file_gbr.py

@@ -1,6 +1,6 @@
 from helper import unittest, PillowTestCase
 
-from PIL import GbrImagePlugin
+from PIL import Image, GbrImagePlugin
 
 
 class TestFileGbr(PillowTestCase):
@@ -12,6 +12,13 @@ class TestFileGbr(PillowTestCase):
                           lambda: GbrImagePlugin.GbrImageFile(invalid_file))
 
 
+    def test_gbr_file(self):
+        im = Image.open('Tests/images/gbr.gbr')
+
+        target = Image.open('Tests/images/gbr.png')
+
+        self.assert_image_equal(target, im)
+
 if __name__ == '__main__':
     unittest.main()