两种方法:
第一种 :直接调用方法​

- (UIImage*)grayscale:(UIImage*)anImage type:(int)type {
    
    CGImageRef imageRef = anImage.CGImage;
    
    size_t width  = CGImageGetWidth(imageRef);
    size_t height = CGImageGetHeight(imageRef);
    
    size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);
    size_t bitsPerPixel = CGImageGetBitsPerPixel(imageRef);
    
    size_t bytesPerRow = CGImageGetBytesPerRow(imageRef);
    
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(imageRef);
    
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    
    
    bool shouldInterpolate = CGImageGetShouldInterpolate(imageRef);
    
    CGColorRenderingIntent intent = CGImageGetRenderingIntent(imageRef);
    
    CGDataProviderRef dataProvider = CGImageGetDataProvider(imageRef);
    
    CFDataRef data = CGDataProviderCopyData(dataProvider);
    
    UInt8 *buffer = (UInt8*)CFDataGetBytePtr(data);
    
    NSUInteger  x, y;
    for (y = 0; y < height; y++) {
        for (x = 0; x < width; x++) {
            UInt8 *tmp;
            tmp = buffer + y * bytesPerRow + x * 4;
            
            UInt8 red,green,blue;
            red = *(tmp + 0);
            green = *(tmp + 1);
            blue = *(tmp + 2);
            
            UInt8 brightness;
            switch (type) {
                   
                case1:
                    brightness = (77 * red + 28 * green + 151 * blue) / 256;
                    *(tmp + 0) = brightness;
                    *(tmp + 1) = brightness;
                    *(tmp + 2) = brightness;
                    break;
                   
                case2:
                    *(tmp + 0) = red;
                    *(tmp + 1) = green * 0.7;
                    *(tmp + 2) = blue * 0.4;
                    break;
                case3:
                    *(tmp + 0) = 255 - red;
                    *(tmp + 1) = 255 - green;
                    *(tmp + 2) = 255 - blue;
                    break;
                default:
                    *(tmp + 0) = red;
                    *(tmp + 1) = green;
                    *(tmp + 2) = blue;
                    break;
            }
        }
    }
    
    
    CFDataRef effectedData = CFDataCreate(NULL, buffer, CFDataGetLength(data));
    
    CGDataProviderRef effectedDataProvider =CGDataProviderCreateWithCFData(effectedData);
    
    CGImageRef effectedCgImage = CGImageCreate(
                                               width, height,
                                               bitsPerComponent, bitsPerPixel, bytesPerRow,
                                               colorSpace, bitmapInfo, effectedDataProvider,
                                               NULL, shouldInterpolate, intent);
    
    UIImage *effectedImage = [[UIImagealloc] initWithCGImage:effectedCgImage];
    
    CGImageRelease(effectedCgImage);
    
    CFRelease(effectedDataProvider);
    
    CFRelease(effectedData);
    
    CFRelease(data);
    
    return effectedImage;
    
}

第二种 写一个UIimage的分类

在.h文件中添加方法:

- (UIImage *) imageWithTintColor:(UIColor *)tintColor;
- (UIImage *) imageWithGradientTintColor:(UIColor *)tintColor;

在.m文件中

- (UIImage *) imageWithTintColor:(UIColor *)tintColor
{
    return [selfimageWithTintColor:tintColorblendMode:kCGBlendModeDestinationIn];
}
- (UIImage *) imageWithGradientTintColor:(UIColor *)tintColor
{
    return [selfimageWithTintColor:tintColor blendMode:kCGBlendModeOverlay];
}
- (UIImage *) imageWithTintColor:(UIColor *)tintColor blendMode:(CGBlendMode)blendMode
{
    //We want to keep alpha, set opaque to NO; Use 0.0f for scale to use the scale factor of the device’s main screen.
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0f);
    [tintColor setFill];
    CGRect bounds = CGRectMake(0, 0, self.size.width, self.size.height);
    UIRectFill(bounds);
    
    //Draw the tinted image in context
    [selfdrawInRect:bounds blendMode:blendMode alpha:1.0f];
    
    UIImage *tintedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return tintedImage;
}