CODEWITHSUNDEEP
iosquartz-core
Martin
Martin

Reputation: 12215

Quartz core : Changing whole layer pixels color

I'm developping an app that paint on layers. Here's a sample code which show the way I paint.

UIImageView * currentLayer = // getting the right layer...
UIGraphicsBeginImageContext(currentLayer.frame.size);
[currentLayer.image drawInRect:currentLayer.bounds];
// Painting...
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
currentLayer.image = img;
UIGraphicsEndImageContext();

So I have an image (1024x768) which have two kinds of pixels:
- painted ones (same colour for each)
- transparent ones

What is the best way to change the color of the whole layer opaque pixels, knowing that all pixels have the same color?

Do I have to redraw each opaque pixel one by one?

EDIT :

as David Rönnqvist suggested, is tryed by masking a filled image with my layer.

The layer which I want to change color is self.image :

// Creating image full of color
CGRect imRect = self.bounds;
UIGraphicsBeginImageContext(imRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [color CGColor]);
CGContextFillRect(context, imRect);
UIImage * fill = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// masking the image
CGImageRef maskRef = [self.image CGImage];
CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                    CGImageGetHeight(maskRef),
                                    CGImageGetBitsPerComponent(maskRef),
                                    CGImageGetBitsPerPixel(maskRef),
                                    CGImageGetBytesPerRow(maskRef),
                                    CGImageGetDataProvider(maskRef), NULL, false);

CGImageRef masked = CGImageCreateWithMask([fill CGImage], mask);
self.image = [UIImage imageWithCGImage:masked];

Almost ! It masks the exact oposite of my layer: only alpha pixels are painted...

Any idea ?

Upvotes: 0

Views: 872

Answers (1)

Martin
Martin

Reputation: 12215

It was very simple, in fact.

UIImage has a method : drawInRect which only draws opaque pixels.

Here's the code (called from an UIImageView):

CGRect rect = self.bounds;
UIGraphicsBeginImageContext(rect.size);
[self.image drawInRect:rect];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetBlendMode(context, kCGBlendModeSourceIn);
CGContextSetFillColorWithColor(context, newColor.CGColor);
CGContextFillRect(context, rect);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Many thanks to iPhone - How do you color an image?

Upvotes: 1

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