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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkBitmap.h"
#include "SkBitmapHasher.h"
#include "SkCityHash.h"
#include "SkEndian.h"
#include "SkImageEncoder.h"
#include "SkStream.h"
/**
* Write an integer value to a stream in little-endian order.
*/
static void write_int_to_buffer(uint32_t val, SkWStream* out) {
val = SkEndian_SwapLE32(val);
for (size_t byte = 0; byte < 4; ++byte) {
out->write8((uint8_t)(val & 0xff));
val = val >> 8;
}
}
/*static*/ bool SkBitmapHasher::ComputeDigestInternal(const SkBitmap& bitmap,
SkHashDigest *result) {
size_t pixelBufferSize = bitmap.width() * bitmap.height() * 4;
size_t totalBufferSize = pixelBufferSize + 2 * sizeof(uint32_t);
SkAutoMalloc bufferManager(totalBufferSize);
char *bufferStart = static_cast<char *>(bufferManager.get());
SkMemoryWStream out(bufferStart, totalBufferSize);
// start with the x/y dimensions
write_int_to_buffer(SkToU32(bitmap.width()), &out);
write_int_to_buffer(SkToU32(bitmap.height()), &out);
// add all the pixel data
SkAutoTDelete<SkImageEncoder> enc(CreateARGBImageEncoder());
if (!enc->encodeStream(&out, bitmap, SkImageEncoder::kDefaultQuality)) {
return false;
}
*result = SkCityHash::Compute64(bufferStart, totalBufferSize);
return true;
}
/*static*/ bool SkBitmapHasher::ComputeDigest(const SkBitmap& bitmap, SkHashDigest *result) {
if (ComputeDigestInternal(bitmap, result)) {
return true;
}
// Hmm, that didn't work. Maybe if we create a new
// kARGB_8888_Config version of the bitmap it will work better?
SkBitmap copyBitmap;
if (!bitmap.copyTo(©Bitmap, SkBitmap::kARGB_8888_Config)) {
return false;
}
return ComputeDigestInternal(copyBitmap, result);
}
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