Add an option on SkImageDecoder to skip writing 0s.

tools/skimage_main.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm_expectations.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 12 matching lines @@
 __SK_FORCE_IMAGE_DECODER_LINKING;
 
 DEFINE_string(config, "None", "Preferred config to decode into. [None|8888|565|A8]");
 DEFINE_string(createExpectationsPath, "", "Path to write JSON expectations.");
 DEFINE_string(mismatchPath, "", "Folder to write mismatched images to.");
 DEFINE_string2(readPath, r, "", "Folder(s) and files to decode images. Required.");
 DEFINE_string(readExpectationsPath, "", "Path to read JSON expectations from.");
 DEFINE_bool(reencode, true, "Reencode the images to test encoding.");
 DEFINE_bool(testSubsetDecoding, true, "Test decoding subsets of images.");
 DEFINE_string2(writePath, w, "",  "Write rendered images into this directory.");
+DEFINE_bool(skip, false, "Skip writing zeroes.");
 
 struct Format {
     SkImageEncoder::Type    fType;
     SkImageDecoder::Format  fFormat;
     const char*             fSuffix;
 };
 
 static const Format gFormats[] = {
     { SkImageEncoder::kBMP_Type, SkImageDecoder::kBMP_Format, ".bmp" },
     { SkImageEncoder::kGIF_Type, SkImageDecoder::kGIF_Format, ".gif" },
@@ skipping 333 matching lines @@
     }
 
     SkImageDecoder* codec = SkImageDecoder::Factory(&stream);
     if (NULL == codec) {
         gMissingCodecs.push_back().set(srcPath);
         return;
     }
 
     SkAutoTDelete<SkImageDecoder> ad(codec);
 
+    codec->setSkipWritingZeroes(FLAGS_skip);
     stream.rewind();
 
     // Create a string representing just the filename itself, for use in json expectations.
     SkString basename = SkOSPath::SkBasename(srcPath);
     const char* filename = basename.c_str();
 
     if (!codec->decode(&stream, &bitmap, gPrefConfig,
                        SkImageDecoder::kDecodePixels_Mode)) {
         if (expect_to_fail(filename)) {
             gSuccessfulDecodes.push_back().appendf(
@@ skipping 301 matching lines @@
     }
 
     return failed ? -1 : 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char * const argv[]) {
     return tool_main(argc, (char**) argv);
 }
 #endif