1
2 /*
3 * Copyright 2012 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9 #include "SkBitmap.h"
10 #include "SkBitmapChecksummer.h"
11 #include "SkBitmapTransformer.h"
12 #include "SkCityHash.h"
13 #include "SkEndian.h"
14
15 /**
16 * Write an integer value into a bytebuffer in little-endian order.
17 */
write_int_to_buffer(int val,char * buf)18 static void write_int_to_buffer(int val, char* buf) {
19 val = SkEndian_SwapLE32(val);
20 for (int byte=0; byte<4; byte++) {
21 *buf++ = (char)(val & 0xff);
22 val = val >> 8;
23 }
24 }
25
Compute64Internal(const SkBitmap & bitmap,const SkBitmapTransformer & transformer)26 /*static*/ uint64_t SkBitmapChecksummer::Compute64Internal(
27 const SkBitmap& bitmap, const SkBitmapTransformer& transformer) {
28 int pixelBufferSize = transformer.bytesNeededTotal();
29 int totalBufferSize = pixelBufferSize + 8; // leave room for x/y dimensions
30
31 SkAutoMalloc bufferManager(totalBufferSize);
32 char *bufferStart = static_cast<char *>(bufferManager.get());
33 char *bufPtr = bufferStart;
34 // start with the x/y dimensions
35 write_int_to_buffer(bitmap.width(), bufPtr);
36 bufPtr += 4;
37 write_int_to_buffer(bitmap.height(), bufPtr);
38 bufPtr += 4;
39
40 // add all the pixel data
41 if (!transformer.copyBitmapToPixelBuffer(bufPtr, pixelBufferSize)) {
42 return 0;
43 }
44 return SkCityHash::Compute64(bufferStart, totalBufferSize);
45 }
46
Compute64(const SkBitmap & bitmap)47 /*static*/ uint64_t SkBitmapChecksummer::Compute64(const SkBitmap& bitmap) {
48 const SkBitmapTransformer::PixelFormat kPixelFormat =
49 SkBitmapTransformer::kARGB_8888_Premul_PixelFormat;
50
51 // First, try to transform the existing bitmap.
52 const SkBitmapTransformer transformer =
53 SkBitmapTransformer(bitmap, kPixelFormat);
54 if (transformer.isValid(false)) {
55 return Compute64Internal(bitmap, transformer);
56 }
57
58 // Hmm, that didn't work. Maybe if we create a new
59 // kARGB_8888_Config version of the bitmap it will work better?
60 SkBitmap copyBitmap;
61 bitmap.copyTo(©Bitmap, SkBitmap::kARGB_8888_Config);
62 const SkBitmapTransformer copyTransformer =
63 SkBitmapTransformer(copyBitmap, kPixelFormat);
64 if (copyTransformer.isValid(true)) {
65 return Compute64Internal(copyBitmap, copyTransformer);
66 } else {
67 return 0;
68 }
69 }
70