Add presubmit script to verify that scaled resources are correct dimensions.

ui/resources/resource_check/resource_scale_factors.py

Index: ui/resources/resource_check/resource_scale_factors.py
diff --git a/ui/resources/resource_check/resource_scale_factors.py b/ui/resources/resource_check/resource_scale_factors.py
new file mode 100644
index 0000000000000000000000000000000000000000..c3118de892989094d4af7daa52b8c97e3c8466c0
--- /dev/null
+++ b/ui/resources/resource_check/resource_scale_factors.py
@@ -0,0 +1,99 @@
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Presubmit script for Chromium browser resources.
+
+See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
+for more details about the presubmit API built into gcl/git cl, and see
+http://www.chromium.org/developers/web-development-style-guide for the rules
+we're checking against here.
+"""
+
+
+import os
+import struct
+
+
+class ResourceScaleFactors(object):
+  """Verifier of image dimensions for Chromium resources.
+
+  This class verifies the image dimensions of resources in the various
+  resource subdirectories.
+
+  Attributes:
+      paths: An array of tuples giving the folders to check and their
+          relevant scale factors. For example:
+
+          [(1, 'default_100_percent'), (2, 'default_200_percent')]
+  """
+
+  def __init__(self, input_api, output_api, paths):
+    """ Initializes ResourceScaleFactors with paths."""
+    self.input_api = input_api
+    self.output_api = output_api
+    self.paths = paths
+
+  def RunChecks(self):
+    """Verifies the scale factors of resources being added or modified.
+
+    Returns:
+        An array of presubmit errors if any images were detected not
+        having the correct dimensions.
+    """
+    def ImageSize(filename):
+      with open(filename, 'rb', buffering=0) as f:
+        data = f.read(24)
+      assert data[:8] == '\x89PNG\r\n\x1A\n' and data[12:16] == 'IHDR'
+      return struct.unpack('>ii', data[16:24])
+
+    # TODO(flackr): This should allow some flexibility for non-integer scale
+    # factors such as allowing any size between the floor and ceiling of
+    # base * scale.
+    def ExpectedSize(base_width, base_height, scale):
+      return round(base_width * scale), round(base_height * scale)
+
+    repository_path = self.input_api.os_path.relpath(
+        self.input_api.PresubmitLocalPath(),
+        self.input_api.change.RepositoryRoot())
+    results = []
+
+    # Check for affected files in any of the paths specified.
+    affected_files = self.input_api.AffectedFiles(include_deletes=False)
+    files = []
+    for f in affected_files:
+      for path_spec in self.paths:
+        path_root = self.input_api.os_path.join(
+            repository_path, path_spec[1])
+        if (f.LocalPath().endswith('.png') and
+            f.LocalPath().startswith(path_root)):
+          # Only save the relative path from the resource directory.
+          relative_path = self.input_api.os_path.relpath(f.LocalPath(),
+              path_root)
+          if relative_path not in files:
+            files.append(relative_path)
+
+    for f in files:
+      base_image = self.input_api.os_path.join(self.paths[0][1], f)
+      if not os.path.exists(base_image):
+        results.append(self.output_api.PresubmitError(
+            'Base image %s does not exist' % self.input_api.os_path.join(
+            repository_path, base_image)))
+        continue
+      base_width, base_height = ImageSize(base_image)
+      # Find all scaled versions of the base image and verify their sizes.
+      for i in range(1, len(self.paths)):
+        image_path = self.input_api.os_path.join(self.paths[i][1], f)
+        if not os.path.exists(image_path):
+          continue
+        # Ensure that each image for a particular scale factor is the
+        # correct scale of the base image.
+        exp_width, exp_height = ExpectedSize(base_width, base_height,
+            self.paths[i][0])
+        width, height = ImageSize(image_path)
+        if width != exp_width or height != exp_height:
+          results.append(self.output_api.PresubmitError(
+              'Image %s is %dx%d, expected to be %dx%d' % (
+              self.input_api.os_path.join(repository_path, image_path),
+              width, height, exp_width, exp_height)))
+    return results