SkImageDecoder_libbmp.cpp revision 5dd45021c37e24cd2c8e91a0f1a1d28a77ad613c 
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 SK_OVERRIDE {
23        return kBMP_Format;
24    }
25
26protected:
27    virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode mode) SK_OVERRIDE;
28
29private:
30    typedef SkImageDecoder INHERITED;
31};
32
33///////////////////////////////////////////////////////////////////////////////
34DEFINE_DECODER_CREATOR(BMPImageDecoder);
35///////////////////////////////////////////////////////////////////////////////
36
37static SkImageDecoder* sk_libbmp_dfactory(SkStream* stream) {
38    static const char kBmpMagic[] = { 'B', 'M' };
39
40
41    char buffer[sizeof(kBmpMagic)];
42
43    if (stream->read(buffer, sizeof(kBmpMagic)) == sizeof(kBmpMagic) &&
44        !memcmp(buffer, kBmpMagic, sizeof(kBmpMagic))) {
45        return SkNEW(SkBMPImageDecoder);
46    }
47    return NULL;
48}
49
50static SkTRegistry<SkImageDecoder*, SkStream*> gReg(sk_libbmp_dfactory);
51
52///////////////////////////////////////////////////////////////////////////////
53
54class SkBmpDecoderCallback : public image_codec::BmpDecoderCallback {
55public:
56    // we don't copy the bitmap, just remember the pointer
57    SkBmpDecoderCallback(bool justBounds) : fJustBounds(justBounds) {}
58
59    // override from BmpDecoderCallback
60    virtual uint8* SetSize(int width, int height) {
61        fWidth = width;
62        fHeight = height;
63        if (fJustBounds) {
64            return NULL;
65        }
66
67        fRGB.setCount(width * height * 3);  // 3 == r, g, b
68        return fRGB.begin();
69    }
70
71    int width() const { return fWidth; }
72    int height() const { return fHeight; }
73    const uint8_t* rgb() const { return fRGB.begin(); }
74
75private:
76    SkTDArray<uint8_t> fRGB;
77    int fWidth;
78    int fHeight;
79    bool fJustBounds;
80};
81
82bool SkBMPImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
83
84    size_t length = stream->getLength();
85    SkAutoMalloc storage(length);
86
87    if (stream->read(storage.get(), length) != length) {
88        return false;
89    }
90
91    const bool justBounds = SkImageDecoder::kDecodeBounds_Mode == mode;
92    SkBmpDecoderCallback callback(justBounds);
93
94    // Now decode the BMP into callback's rgb() array [r,g,b, r,g,b, ...]
95    {
96        image_codec::BmpDecoderHelper helper;
97        const int max_pixels = 16383*16383; // max width*height
98        if (!helper.DecodeImage((const char*)storage.get(), length,
99                                max_pixels, &callback)) {
100            return false;
101        }
102    }
103
104    // we don't need this anymore, so free it now (before we try to allocate
105    // the bitmap's pixels) rather than waiting for its destructor
106    storage.free();
107
108    int width = callback.width();
109    int height = callback.height();
110    SkBitmap::Config config = this->getPrefConfig(k32Bit_SrcDepth, false);
111
112    // only accept prefConfig if it makes sense for us
113    if (SkBitmap::kARGB_4444_Config != config &&
114            SkBitmap::kRGB_565_Config != config) {
115        config = SkBitmap::kARGB_8888_Config;
116    }
117
118    SkScaledBitmapSampler sampler(width, height, getSampleSize());
119
120    if (justBounds) {
121        bm->setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
122        bm->setIsOpaque(true);
123        return true;
124    }
125    // No Bitmap reuse supported for this format
126    if (!bm->isNull()) {
127        return false;
128    }
129
130    bm->setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
131    bm->setIsOpaque(true);
132
133    if (!this->allocPixelRef(bm, NULL)) {
134        return false;
135    }
136
137    SkAutoLockPixels alp(*bm);
138
139    if (!sampler.begin(bm, SkScaledBitmapSampler::kRGB, getDitherImage())) {
140        return false;
141    }
142
143    const int srcRowBytes = width * 3;
144    const int dstHeight = sampler.scaledHeight();
145    const uint8_t* srcRow = callback.rgb();
146
147    srcRow += sampler.srcY0() * srcRowBytes;
148    for (int y = 0; y < dstHeight; y++) {
149        sampler.next(srcRow);
150        srcRow += sampler.srcDY() * srcRowBytes;
151    }
152    return true;
153}
154