iOS开发之UIImage黑白处理

//通过修改图片饱和度将图片变为黑白（镂空位置不影响）

- (UIImage*) convertImageToGreyScale:(UIImage*) image

{

    CIImage *beginImage = [CIImage imageWithCGImage:image.CGImage];

    CIFilter * filter = [CIFilter filterWithName:@"CIColorControls"];

    [filter setValue:beginImage forKey:kCIInputImageKey];

    //饱和度 0---2 默认为1

    [filter setValue:[NSNumber numberWithFloat:0] forKey:@"inputSaturation"];

    // 得到过滤后的图片

    CIImage *outputImage = [filter outputImage];

    // 转换图片, 创建基于GPU的CIContext对象

    CIContext *context = [CIContext contextWithOptions: nil];

    CGImageRef cgimg = [context createCGImage:outputImage fromRect:[outputImage extent]];

    UIImage *newImg = [UIImage imageWithCGImage:cgimg];

    // 释放C对象

    CGImageRelease(cgimg);

    return newImg;

}

//将图片变为黑边反转（镂空部位为黑色）

- (UIImage*) convertImageToGreyScale:(UIImage*) image {

　　CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height);

　　CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

　　CGContextRef context = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, 0, colorSpace, kCGImageAlphaNone);

　　CGContextDrawImage(context, imageRect, [image CGImage]);

　　CGImageRef imageRef = CGBitmapContextCreateImage(context);

　　UIImage *newImage = [UIImage imageWithCGImage:imageRef];

　　CGColorSpaceRelease(colorSpace); CGContextRelease(context);

　　CFRelease(imageRef);

　　return newImage;

}