CGImageRef YYCGImageCreateWithWebPData()

in iOS/WAStickersThirdParty/YYImageCoder.m [1314:1436]
101 lines of code
32 McCabe index (conditional complexity)

CGImageRef YYCGImageCreateWithWebPData(CFDataRef webpData,
                                       BOOL decodeForDisplay,
                                       BOOL useThreads,
                                       BOOL bypassFiltering,
                                       BOOL noFancyUpsampling) {
    /*
     Call WebPDecode() on a multi-frame webp data will get an error (VP8_STATUS_UNSUPPORTED_FEATURE).
     Use WebPDemuxer to unpack it first.
     */
    WebPData data = {0};
    WebPDemuxer *demuxer = NULL;
    
    int frameCount = 0, canvasWidth = 0, canvasHeight = 0;
    WebPIterator iter = {0};
    BOOL iterInited = NO;
    const uint8_t *payload = NULL;
    size_t payloadSize = 0;
    WebPDecoderConfig config = {0};
    
    BOOL hasAlpha = NO;
    size_t bitsPerComponent = 0, bitsPerPixel = 0, bytesPerRow = 0, destLength = 0;
    CGBitmapInfo bitmapInfo = 0;
    WEBP_CSP_MODE colorspace = 0;
    void *destBytes = NULL;
    CGDataProviderRef provider = NULL;
    CGImageRef imageRef = NULL;
    
    if (!webpData || CFDataGetLength(webpData) == 0) return NULL;
    data.bytes = CFDataGetBytePtr(webpData);
    data.size = CFDataGetLength(webpData);
    demuxer = WebPDemux(&data);
    if (!demuxer) goto fail;
    
    frameCount = WebPDemuxGetI(demuxer, WEBP_FF_FRAME_COUNT);
    if (frameCount == 0) {
        goto fail;
        
    } else if (frameCount == 1) { // single-frame
        payload = data.bytes;
        payloadSize = data.size;
        if (!WebPInitDecoderConfig(&config)) goto fail;
        if (WebPGetFeatures(payload , payloadSize, &config.input) != VP8_STATUS_OK) goto fail;
        canvasWidth = config.input.width;
        canvasHeight = config.input.height;
        
    } else { // multi-frame
        canvasWidth = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_WIDTH);
        canvasHeight = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_HEIGHT);
        if (canvasWidth < 1 || canvasHeight < 1) goto fail;
        
        if (!WebPDemuxGetFrame(demuxer, 1, &iter)) goto fail;
        iterInited = YES;
        
        if (iter.width > canvasWidth || iter.height > canvasHeight) goto fail;
        payload = iter.fragment.bytes;
        payloadSize = iter.fragment.size;
        
        if (!WebPInitDecoderConfig(&config)) goto fail;
        if (WebPGetFeatures(payload , payloadSize, &config.input) != VP8_STATUS_OK) goto fail;
    }
    if (payload == NULL || payloadSize == 0) goto fail;
    
    hasAlpha = config.input.has_alpha;
    bitsPerComponent = 8;
    bitsPerPixel = 32;
    bytesPerRow = YYImageByteAlign(bitsPerPixel / 8 * canvasWidth, 32);
    destLength = bytesPerRow * canvasHeight;
    if (decodeForDisplay) {
        bitmapInfo = kCGBitmapByteOrder32Host;
        bitmapInfo |= hasAlpha ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaNoneSkipFirst;
        colorspace = MODE_bgrA; // small endian
    } else {
        bitmapInfo = kCGBitmapByteOrderDefault;
        bitmapInfo |= hasAlpha ? kCGImageAlphaLast : kCGImageAlphaNoneSkipLast;
        colorspace = MODE_RGBA;
    }
    destBytes = calloc(1, destLength);
    if (!destBytes) goto fail;
    
    config.options.use_threads = useThreads; //speed up 23%
    config.options.bypass_filtering = bypassFiltering; //speed up 11%, cause some banding
    config.options.no_fancy_upsampling = noFancyUpsampling; //speed down 16%, lose some details
    config.output.colorspace = colorspace;
    config.output.is_external_memory = 1;
    config.output.u.RGBA.rgba = destBytes;
    config.output.u.RGBA.stride = (int)bytesPerRow;
    config.output.u.RGBA.size = destLength;
    
    VP8StatusCode result = WebPDecode(payload, payloadSize, &config);
    if ((result != VP8_STATUS_OK) && (result != VP8_STATUS_NOT_ENOUGH_DATA)) goto fail;
    
    if (iter.x_offset != 0 || iter.y_offset != 0) {
        void *tmp = calloc(1, destLength);
        if (tmp) {
            vImage_Buffer src = {destBytes, canvasHeight, canvasWidth, bytesPerRow};
            vImage_Buffer dest = {tmp, canvasHeight, canvasWidth, bytesPerRow};
            vImage_CGAffineTransform transform = {1, 0, 0, 1, iter.x_offset, -iter.y_offset};
            uint8_t backColor[4] = {0};
            vImageAffineWarpCG_ARGB8888(&src, &dest, NULL, &transform, backColor, kvImageBackgroundColorFill);
            memcpy(destBytes, tmp, destLength);
            free(tmp);
        }
    }
    
    provider = CGDataProviderCreateWithData(destBytes, destBytes, destLength, YYCGDataProviderReleaseDataCallback);
    if (!provider) goto fail;
    destBytes = NULL; // hold by provider
    
    imageRef = CGImageCreate(canvasWidth, canvasHeight, bitsPerComponent, bitsPerPixel, bytesPerRow, YYCGColorSpaceGetDeviceRGB(), bitmapInfo, provider, NULL, false, kCGRenderingIntentDefault);
    
    CFRelease(provider);
    if (iterInited) WebPDemuxReleaseIterator(&iter);
    WebPDemuxDelete(demuxer);
    
    return imageRef;
    
fail:
    if (destBytes) free(destBytes);
    if (provider) CFRelease(provider);
    if (iterInited) WebPDemuxReleaseIterator(&iter);
    if (demuxer) WebPDemuxDelete(demuxer);
    return NULL;
}