user3422862 user3422862 - 1 year ago 127
Objective-C Question

Apply Black and White Filter to UIImage

I need to apply black and white filter on UIImage. I Have a view when there appear a photo taked by the user. But i don't have any ideas for transform the colors of image.

- (void)viewDidLoad {
[super viewDidLoad];
self.navigationItem.title = NSLocalizedString(@"#Paint!", nil);
imageView.image = image;

Answer Source
- (UIImage *)convertImageToGrayScale:(UIImage *)image {

    // Create image rectangle with current image width/height
    CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height);

    // Grayscale color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

    // Create bitmap content with current image size and grayscale colorspace
    CGContextRef context = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, 0, colorSpace, kCGImageAlphaNone);

    // Draw image into current context, with specified rectangle
    // using previously defined context (with grayscale colorspace)
    CGContextDrawImage(context, imageRect, [image 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

    // Return the new grayscale image
    return newImage; }