iOS设置图片不可用 置灰效果的实现

-(UIImage *)unableImage:(UIImage*)originImage{

    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *superImage = [CIImage imageWithCGImage:originImage.CGImage];
    CIFilter *lighten = [CIFilter filterWithName:@"CIColorControls"];
    [lighten setValue:superImage forKey:kCIInputImageKey];
//    // 修改亮度   -1---1   数越大越亮
    [lighten setValue:@(0) forKey:@"inputBrightness"];
    
    // 修改饱和度  0---2
    [lighten setValue:@(0) forKey:@"inputSaturation"];
    
//    // 修改对比度  0---4
    [lighten setValue:@(0.5) forKey:@"inputContrast"];
    CIImage *result = [lighten valueForKey:kCIOutputImageKey];
    CGImageRef cgImage = [context createCGImage:result fromRect:[superImage extent]];
    // 得到修改后的图片
    UIImage *newImage =  [UIImage imageWithCGImage:cgImage];
    // 释放对象
    CGImageRelease(cgImage);
    return newImage;
}