C++ SkAutoMalloc::alloc方法代码示例

bool SkJPEGImageDecoder::onDecode(SkStream* stream, SkBitmap* bm,
                                  SkBitmap::Config prefConfig, Mode mode) {
#ifdef TIME_DECODE
    AutoTimeMillis atm("JPEG Decode");
#endif

    SkAutoMalloc  srcStorage;
    JPEGAutoClean autoClean;

    jpeg_decompress_struct  cinfo;
    sk_error_mgr            sk_err;
    sk_source_mgr           sk_stream(stream);

    cinfo.err = jpeg_std_error(&sk_err);
    sk_err.error_exit = sk_error_exit;

    // All objects need to be instantiated before this setjmp call so that
    // they will be cleaned up properly if an error occurs.
    if (setjmp(sk_err.fJmpBuf)) {
        return false;
    }

    jpeg_create_decompress(&cinfo);
    autoClean.set(&cinfo);

    //jpeg_stdio_src(&cinfo, file);
    cinfo.src = &sk_stream;

    jpeg_read_header(&cinfo, true);

    /*  Try to fulfill the requested sampleSize. Since jpeg can do it (when it
        can) much faster that we, just use their num/denom api to approximate
        the size.
    */
    int sampleSize = this->getSampleSize();

    cinfo.dct_method = JDCT_IFAST;
    cinfo.scale_num = 1;
    cinfo.scale_denom = sampleSize;

    /*  image_width and image_height are the original dimensions, available
        after jpeg_read_header(). To see the scaled dimensions, we have to call
        jpeg_start_decompress(), and then read output_width and output_height.
    */
    jpeg_start_decompress(&cinfo);

    /*  If we need to better match the request, we might examine the image and
        output dimensions, and determine if the downsampling jpeg provided is
        not sufficient. If so, we can recompute a modified sampleSize value to
        make up the difference.
        
        To skip this additional scaling, just set sampleSize = 1; below.
    */
    sampleSize = sampleSize * cinfo.output_width / cinfo.image_width;

    // check for supported formats
    bool isRGB; // as opposed to gray8
    if (3 == cinfo.num_components && JCS_RGB == cinfo.out_color_space) {
        isRGB = true;
    } else if (1 == cinfo.num_components &&
               JCS_GRAYSCALE == cinfo.out_color_space) {
        isRGB = false;  // could use Index8 config if we want...
    } else {
        SkDEBUGF(("SkJPEGImageDecoder: unsupported jpeg colorspace %d with %d components\n",
                    cinfo.jpeg_color_space, cinfo.num_components));
        return false;
    }
    
    SkBitmap::Config config = prefConfig;
    // if no user preference, see what the device recommends
    if (config == SkBitmap::kNo_Config)
        config = SkImageDecoder::GetDeviceConfig();

    // only these make sense for jpegs
    if (config != SkBitmap::kARGB_8888_Config &&
            config != SkBitmap::kARGB_4444_Config &&
            config != SkBitmap::kRGB_565_Config) {
        config = SkBitmap::kARGB_8888_Config;
    }

    // should we allow the Chooser (if present) to pick a config for us???
    if (!this->chooseFromOneChoice(config, cinfo.output_width,
                                   cinfo.output_height)) {
        return false;
    }

    SkScaledBitmapSampler sampler(cinfo.output_width, cinfo.output_height,
                                  sampleSize);
    
    bm->setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
    // jpegs are always opauqe (i.e. have no per-pixel alpha)
    bm->setIsOpaque(true);

    if (SkImageDecoder::kDecodeBounds_Mode == mode) {
        return true;
    }
    if (!this->allocPixelRef(bm, NULL)) {
        return false;
    }

//.........这里部分代码省略.........