michael@0: /*
michael@0:  * Copyright 2012 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #include "SkBitmap.h"
michael@0: #include "SkBitmapHasher.h"
michael@0: #include "SkEndian.h"
michael@0: #include "SkImageEncoder.h"
michael@0: 
michael@0: #include "SkMD5.h"
michael@0: 
michael@0: /**
michael@0:  * Write an int32 value to a stream in little-endian order.
michael@0:  */
michael@0: static void write_int32_to_buffer(uint32_t val, SkWStream* out) {
michael@0:     val = SkEndian_SwapLE32(val);
michael@0:     for (size_t byte = 0; byte < 4; ++byte) {
michael@0:         out->write8((uint8_t)(val & 0xff));
michael@0:         val = val >> 8;
michael@0:     }
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Return the first 8 bytes of a bytearray, encoded as a little-endian uint64.
michael@0:  */
michael@0: static inline uint64_t first_8_bytes_as_uint64(const uint8_t *bytearray) {
michael@0:     return SkEndian_SwapLE64(*(reinterpret_cast<const uint64_t *>(bytearray)));
michael@0: }
michael@0: 
michael@0: /*static*/ bool SkBitmapHasher::ComputeDigestInternal(const SkBitmap& bitmap, uint64_t *result) {
michael@0:     SkMD5 out;
michael@0: 
michael@0:     // start with the x/y dimensions
michael@0:     write_int32_to_buffer(SkToU32(bitmap.width()), &out);
michael@0:     write_int32_to_buffer(SkToU32(bitmap.height()), &out);
michael@0: 
michael@0:     // add all the pixel data
michael@0:     SkAutoTDelete<SkImageEncoder> enc(CreateARGBImageEncoder());
michael@0:     if (!enc->encodeStream(&out, bitmap, SkImageEncoder::kDefaultQuality)) {
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     SkMD5::Digest digest;
michael@0:     out.finish(digest);
michael@0:     *result = first_8_bytes_as_uint64(digest.data);
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: /*static*/ bool SkBitmapHasher::ComputeDigest(const SkBitmap& bitmap, uint64_t *result) {
michael@0:     if (ComputeDigestInternal(bitmap, result)) {
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     // Hmm, that didn't work. Maybe if we create a new
michael@0:     // kARGB_8888_Config version of the bitmap it will work better?
michael@0:     SkBitmap copyBitmap;
michael@0:     if (!bitmap.copyTo(&copyBitmap, kPMColor_SkColorType)) {
michael@0:         return false;
michael@0:     }
michael@0:     return ComputeDigestInternal(copyBitmap, result);
michael@0: }