SkImageDecoder_libbmp.cpp revision 2a2cc2057347553f07d933b021876ba5502e55cd 
1
2/*
3 * Copyright 2007 The Android Open Source Project
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
10#include "bmpdecoderhelper.h"
11#include "SkImageDecoder.h"
12#include "SkScaledBitmapSampler.h"
13#include "SkStream.h"
14#include "SkColorPriv.h"
15#include "SkTDArray.h"
16#include "SkTRegistry.h"
17
18class SkBMPImageDecoder : public SkImageDecoder {
19public:
20    SkBMPImageDecoder() {}
21
22    virtual Format getFormat() const {
23        return kBMP_Format;
24    }
25
26protected:
27    virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode mode);
28};
29
30///////////////////////////////////////////////////////////////////////////////
31DEFINE_DECODER_CREATOR(BMPImageDecoder);
32///////////////////////////////////////////////////////////////////////////////
33
34static SkImageDecoder* sk_libbmp_dfactory(SkStream* stream) {
35    static const char kBmpMagic[] = { 'B', 'M' };
36
37    size_t len = stream->getLength();
38    char buffer[sizeof(kBmpMagic)];
39
40    if (len > sizeof(kBmpMagic) &&
41            stream->read(buffer, sizeof(kBmpMagic)) == sizeof(kBmpMagic) &&
42            !memcmp(buffer, kBmpMagic, sizeof(kBmpMagic))) {
43        return SkNEW(SkBMPImageDecoder);
44    }
45    return NULL;
46}
47
48static SkTRegistry<SkImageDecoder*, SkStream*> gReg(sk_libbmp_dfactory);
49
50///////////////////////////////////////////////////////////////////////////////
51
52class SkBmpDecoderCallback : public image_codec::BmpDecoderCallback {
53public:
54    // we don't copy the bitmap, just remember the pointer
55    SkBmpDecoderCallback(bool justBounds) : fJustBounds(justBounds) {}
56
57    // override from BmpDecoderCallback
58    virtual uint8* SetSize(int width, int height) {
59        fWidth = width;
60        fHeight = height;
61        if (fJustBounds) {
62            return NULL;
63        }
64
65        fRGB.setCount(width * height * 3);  // 3 == r, g, b
66        return fRGB.begin();
67    }
68
69    int width() const { return fWidth; }
70    int height() const { return fHeight; }
71    uint8_t* rgb() const { return fRGB.begin(); }
72
73private:
74    SkTDArray<uint8_t> fRGB;
75    int fWidth;
76    int fHeight;
77    bool fJustBounds;
78};
79
80bool SkBMPImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
81
82    size_t length = stream->getLength();
83    SkAutoMalloc storage(length);
84
85    if (stream->read(storage.get(), length) != length) {
86        return false;
87    }
88
89    const bool justBounds = SkImageDecoder::kDecodeBounds_Mode == mode;
90    SkBmpDecoderCallback callback(justBounds);
91
92    // Now decode the BMP into callback's rgb() array [r,g,b, r,g,b, ...]
93    {
94        image_codec::BmpDecoderHelper helper;
95        const int max_pixels = 16383*16383; // max width*height
96        if (!helper.DecodeImage((const char*)storage.get(), length,
97                                max_pixels, &callback)) {
98            return false;
99        }
100    }
101
102    // we don't need this anymore, so free it now (before we try to allocate
103    // the bitmap's pixels) rather than waiting for its destructor
104    storage.free();
105
106    int width = callback.width();
107    int height = callback.height();
108    SkBitmap::Config config = this->getPrefConfig(k32Bit_SrcDepth, false);
109
110    // only accept prefConfig if it makes sense for us
111    if (SkBitmap::kARGB_4444_Config != config &&
112            SkBitmap::kRGB_565_Config != config) {
113        config = SkBitmap::kARGB_8888_Config;
114    }
115
116    SkScaledBitmapSampler sampler(width, height, getSampleSize());
117
118    bm->setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
119    bm->setIsOpaque(true);
120    if (justBounds) {
121        return true;
122    }
123
124    if (!this->allocPixelRef(bm, NULL)) {
125        return false;
126    }
127
128    SkAutoLockPixels alp(*bm);
129
130    if (!sampler.begin(bm, SkScaledBitmapSampler::kRGB, getDitherImage())) {
131        return false;
132    }
133
134    const int srcRowBytes = width * 3;
135    const int dstHeight = sampler.scaledHeight();
136    const uint8_t* srcRow = callback.rgb();
137
138    srcRow += sampler.srcY0() * srcRowBytes;
139    for (int y = 0; y < dstHeight; y++) {
140        sampler.next(srcRow);
141        srcRow += sampler.srcDY() * srcRowBytes;
142    }
143    return true;
144}
145