XFA: Support PNG format in pdfium_test and add image diffing

Lays the groundwork for pixel-diffing tests in pdfium.

This is a port of chromium's tools/image_diff/image_diff_png.cc onto the
top of the fxcodec-provided version of libpng. pdfium_test is modified
to support the new format, and the tools/image_diff.cc image comparison
utility is provided, stripped of its base/ dependencies.

Unfortunately, this can't be back-ported to origin/main, since the
underlying PNG support isn't present inside pdfium.

BUG=https://code.google.com/p/pdfium/issues/detail?id=62
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/870203005

1 files changed, 34 insertions, 0 deletions

diff --git a/samples/image_diff_png.h b/samples/image_diff_png.h
new file mode 100644
index 0000000000..ea77e9a98f
--- /dev/null
+++ b/samples/image_diff_png.h
@@ -0,0 +1,34 @@
+// Copyright 2013 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.
+
+#ifndef TOOLS_IMAGEDIFF_IMAGE_DIFF_PNG_H_
+#define TOOLS_IMAGEDIFF_IMAGE_DIFF_PNG_H_
+
+#include <vector>
+
+namespace image_diff_png {
+
+// Decode a PNG into an RGBA pixel array.
+bool DecodePNG(const unsigned char* input, size_t input_size,
+               std::vector<unsigned char>* output,
+               int* width, int* height);
+
+// Encode an RGBA pixel array into a PNG.
+bool EncodeRGBAPNG(const unsigned char* input,
+                   int width,
+                   int height,
+                   int row_byte_width,
+                   std::vector<unsigned char>* output);
+
+// Encode an BGRA pixel array into a PNG.
+bool EncodeBGRAPNG(const unsigned char* input,
+                   int width,
+                   int height,
+                   int row_byte_width,
+                   bool discard_transparency,
+                   std::vector<unsigned char>* output);
+
+}  // namespace image_diff_png
+
+#endif  // TOOLS_IMAGEDIFF_IMAGE_DIFF_PNG_H_