返回图像的灰度模式

gistfile1.m

+ (UIImage *) grayscaleImage: (UIImage *) image
{
    CGSize size = image.size;
    CGRect rect = CGRectMake(0.0f, 0.0f, image.size.width,
        image.size.height);
    // Create a mono/gray color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate(nil, size.width,
        size.height, 8, 0, colorSpace, kCGImageAlphaNone);
    CGColorSpaceRelease(colorSpace);
    // Draw the image into the grayscale context
    CGContextDrawImage(context, rect, [image CGImage]);
    CGImageRef grayscale = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    // Recover the image
    UIImage *img = [UIImage imageWithCGImage:grayscale];
    CFRelease(grayscale);
    return img;
}