Imagen a Grayscale

gistfile1.m

+ (UIImage *)convertImageToGrayScale:(UIImage *)img
{
    // Create image rectangle with current image width/height
    CGRect imageRect = CGRectMake(0, 0, img.size.width, img.size.height);
    
    // Grayscale color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    
    // Create bitmap content with current image size and grayscale colorspace
    CGContextRef context = CGBitmapContextCreate(nil, img.size.width, img.size.height, 8, 0, colorSpace, kCGImageAlphaNone);
    
    // Draw image into current context, with specified rectangle
    // using previously defined context (with grayscale colorspace)
    CGContextDrawImage(context, imageRect, [img CGImage]);
    
    // Create bitmap image info from pixel data in current context
    CGImageRef imageRef = CGBitmapContextCreateImage(context);
    
    // Create a new UIImage object  
    UIImage *newImage = [UIImage imageWithCGImage:imageRef];
    
    // Release colorspace, context and bitmap information
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    if (imageRef)
        CFRelease(imageRef);
    
    // Return the new grayscale image
    return newImage;
}