处理图片颜色
- (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) {
                case 1:
                    brightness = (77 * red + 28 * green + 151 * blue) / 256;
                    *(tmp + 0) = brightness;
                    *(tmp + 1) = brightness;
                    *(tmp + 2) = brightness;
                    break;
                case 2:
                    *(tmp + 0) = red;
                    *(tmp + 1) = green * 0.7;
                    *(tmp + 2) = blue * 0.4;
                    break;
                case 3:
                    *(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 = [[UIImage alloc] initWithCGImage:effectedCgImage];
    CGImageRelease(effectedCgImage);
    CFRelease(effectedDataProvider);
    CFRelease(effectedData);
    CFRelease(data);
    return effectedImage;
}