webp解码Mac、iOS兼容

CGBitmapInfo 在Mac与iOS平台需要区分初始化，不然会解码失败。

+ (nullable UIImage *)sd_rawWebpImageWithData:(WebPData)webpData {
    WebPDecoderConfig config;
    if (!WebPInitDecoderConfig(&config)) {
        return nil;
    }
    
    if (WebPGetFeatures(webpData.bytes, webpData.size, &config.input) != VP8_STATUS_OK) {
        return nil;
    }
    
    if ([[UIDevice currentDevice].systemVersion floatValue] >=12.0) {
        //ios 12中系统api不再兼容24bpp,8bpc的组合，这里让webp无论是否存在alpha通道都输出4个components
        config.output.colorspace = MODE_rgbA;
    } else {
        config.output.colorspace = config.input.has_alpha ? MODE_rgbA : MODE_RGB;
    }
    
    config.options.use_threads = 1;
    
    // Decode the WebP image data into a RGBA value array.
    if (WebPDecode(webpData.bytes, webpData.size, &config) != VP8_STATUS_OK) {
        return nil;
    }
    
    int width = config.input.width;
    int height = config.input.height;
    if (config.options.use_scaling) {
        width = config.options.scaled_width;
        height = config.options.scaled_height;
    }
    
    // Construct a UIImage from the decoded RGBA value array.
    CGDataProviderRef provider =
    CGDataProviderCreateWithData(NULL, config.output.u.RGBA.rgba, config.output.u.RGBA.size, FreeImageData);
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    
// 这里需要注意，Mac与iOS端 CGBitmapInfo 需要分别处理
#if TARGET_OS_MACCATALYST
    CGBitmapInfo bitmapInfo;
    // `CGBitmapContextCreate` does not support RGB888 on iOS. Where `CGImageCreate` supports.
    if (!config.input.has_alpha) {
        // RGB888
        bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaNone;
    } else {
        // RGBA8888
        bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast;
    }
#else
    
    CGBitmapInfo bitmapInfo = config.input.has_alpha ? kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast : kCGBitmapByteOrder32Big | kCGImageAlphaNoneSkipLast;
#endif
    
    size_t components = config.input.has_alpha ? 4 : 3;
    if ([[UIDevice currentDevice].systemVersion floatValue] >=12.0) {
        //同上修改,ios 12中使用MODE_rgbA, components数量与has_alpha无关，均为4
        components = 4;
    }
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
    CGImageRef imageRef = CGImageCreate(width, height, 8, components * 8, components * width, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
    
    CGColorSpaceRelease(colorSpaceRef);
    CGDataProviderRelease(provider);
    
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    
    CGImageRelease(imageRef);
    
    return image;
}