static BOOL YYCGImageDecodeToBitmapBufferWith32BitFormat()

in iOS/WAStickersThirdParty/YYImageCoder.m [754:866]
98 lines of code
29 McCabe index (conditional complexity)

static BOOL YYCGImageDecodeToBitmapBufferWith32BitFormat(CGImageRef srcImage, vImage_Buffer *dest, CGBitmapInfo bitmapInfo) {
    if (!srcImage || !dest) return NO;
    size_t width = CGImageGetWidth(srcImage);
    size_t height = CGImageGetHeight(srcImage);
    if (width == 0 || height == 0) return NO;
    
    BOOL hasAlpha = NO;
    BOOL alphaFirst = NO;
    BOOL alphaPremultiplied = NO;
    BOOL byteOrderNormal = NO;
    
    switch (bitmapInfo & kCGBitmapAlphaInfoMask) {
        case kCGImageAlphaPremultipliedLast: {
            hasAlpha = YES;
            alphaPremultiplied = YES;
        } break;
        case kCGImageAlphaPremultipliedFirst: {
            hasAlpha = YES;
            alphaPremultiplied = YES;
            alphaFirst = YES;
        } break;
        case kCGImageAlphaLast: {
            hasAlpha = YES;
        } break;
        case kCGImageAlphaFirst: {
            hasAlpha = YES;
            alphaFirst = YES;
        } break;
        case kCGImageAlphaNoneSkipLast: {
        } break;
        case kCGImageAlphaNoneSkipFirst: {
            alphaFirst = YES;
        } break;
        default: {
            return NO;
        } break;
    }
    
    switch (bitmapInfo & kCGBitmapByteOrderMask) {
        case kCGBitmapByteOrderDefault: {
            byteOrderNormal = YES;
        } break;
        case kCGBitmapByteOrder32Little: {
        } break;
        case kCGBitmapByteOrder32Big: {
            byteOrderNormal = YES;
        } break;
        default: {
            return NO;
        } break;
    }
    
    /*
     Try convert with vImageConvert_AnyToAny() (avaliable since iOS 7.0).
     If fail, try decode with CGContextDrawImage().
     CGBitmapContext use a premultiplied alpha format, unpremultiply may lose precision.
     */
    vImage_CGImageFormat destFormat = {0};
    destFormat.bitsPerComponent = 8;
    destFormat.bitsPerPixel = 32;
    destFormat.colorSpace = YYCGColorSpaceGetDeviceRGB();
    destFormat.bitmapInfo = bitmapInfo;
    dest->data = NULL;
    if (YYCGImageDecodeToBitmapBufferWithAnyFormat(srcImage, dest, &destFormat)) return YES;
    
    CGBitmapInfo contextBitmapInfo = bitmapInfo & kCGBitmapByteOrderMask;
    if (!hasAlpha || alphaPremultiplied) {
        contextBitmapInfo |= (bitmapInfo & kCGBitmapAlphaInfoMask);
    } else {
        contextBitmapInfo |= alphaFirst ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaPremultipliedLast;
    }
    CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, 0, YYCGColorSpaceGetDeviceRGB(), contextBitmapInfo);
    if (!context) goto fail;
    
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), srcImage); // decode and convert
    size_t bytesPerRow = CGBitmapContextGetBytesPerRow(context);
    size_t length = height * bytesPerRow;
    void *data = CGBitmapContextGetData(context);
    if (length == 0 || !data) goto fail;
    
    dest->data = malloc(length);
    dest->width = width;
    dest->height = height;
    dest->rowBytes = bytesPerRow;
    if (!dest->data) goto fail;
    
    if (hasAlpha && !alphaPremultiplied) {
        vImage_Buffer tmpSrc = {0};
        tmpSrc.data = data;
        tmpSrc.width = width;
        tmpSrc.height = height;
        tmpSrc.rowBytes = bytesPerRow;
        vImage_Error error;
        if (alphaFirst && byteOrderNormal) {
            error = vImageUnpremultiplyData_ARGB8888(&tmpSrc, dest, kvImageNoFlags);
        } else {
            error = vImageUnpremultiplyData_RGBA8888(&tmpSrc, dest, kvImageNoFlags);
        }
        if (error != kvImageNoError) goto fail;
    } else {
        memcpy(dest->data, data, length);
    }
    
    CFRelease(context);
    return YES;
    
fail:
    if (context) CFRelease(context);
    if (dest->data) free(dest->data);
    dest->data = NULL;
    return NO;
    return NO;
}