1 /* 2 * Copyright 2012 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #include "SkBitmap.h" 9 #include "SkBitmapHasher.h" 10 #include "SkEndian.h" 11 #include "SkImageEncoder.h" 12 13 #include "SkMD5.h" 14 15 /** 16 * Write an int32 value to a stream in little-endian order. 17 */ 18 static void write_int32_to_buffer(uint32_t val, SkWStream* out) { 19 val = SkEndian_SwapLE32(val); 20 for (size_t byte = 0; byte < 4; ++byte) { 21 out->write8((uint8_t)(val & 0xff)); 22 val = val >> 8; 23 } 24 } 25 26 /** 27 * Return the first 8 bytes of a bytearray, encoded as a little-endian uint64. 28 */ 29 static inline uint64_t first_8_bytes_as_uint64(const uint8_t *bytearray) { 30 return SkEndian_SwapLE64(*(reinterpret_cast<const uint64_t *>(bytearray))); 31 } 32 33 /*static*/ bool SkBitmapHasher::ComputeDigestInternal(const SkBitmap& bitmap, uint64_t *result) { 34 SkMD5 out; 35 36 // start with the x/y dimensions 37 write_int32_to_buffer(SkToU32(bitmap.width()), &out); 38 write_int32_to_buffer(SkToU32(bitmap.height()), &out); 39 40 // add all the pixel data 41 SkAutoTDelete<SkImageEncoder> enc(CreateARGBImageEncoder()); 42 if (!enc->encodeStream(&out, bitmap, SkImageEncoder::kDefaultQuality)) { 43 return false; 44 } 45 46 SkMD5::Digest digest; 47 out.finish(digest); 48 *result = first_8_bytes_as_uint64(digest.data); 49 return true; 50 } 51 52 /*static*/ bool SkBitmapHasher::ComputeDigest(const SkBitmap& bitmap, uint64_t *result) { 53 if (ComputeDigestInternal(bitmap, result)) { 54 return true; 55 } 56 57 // Hmm, that didn't work. Maybe if we create a new 58 // version of the bitmap it will work better? 59 SkBitmap copyBitmap; 60 if (!bitmap.copyTo(©Bitmap, kN32_SkColorType)) { 61 return false; 62 } 63 return ComputeDigestInternal(copyBitmap, result); 64 } 65
