iOS: Change black color in UIImage to another color

Question

I have an image with white border and black color filled inside it. I want to just change the black color to another color at runtime. The user will select the color at runtime in HSB format. How can I do that? I tried CGImageCreateWithMaskingColors by taking const float colorMasking[4]={255, 255, 255, 255}; but I am getting a nil CGImageRef everytime. Please help.

- (UIImage*) maskBlackInImage :(UIImage*) image color:(UIColor*)color
{
    const CGFloat colorMasking[4] = { 222, 255, 222, 255 };
    CGImageRef imageRef = CGImageCreateWithMaskingColors(image.CGImage, colorMasking);
    UIImage* imageB = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return imageB;

}

I am attaching the image of bulb - Bulb with Black color filled, white border and transparent background

Update:

I was able to fill black color with another color after using the code in the accepted answer. But, I could see a little bit of color on white border. The image doesn't look that sharp. Attaching the output:

Output - black filled with color

score 9 · Accepted Answer · edited Sep 18 '15 at 13:39

9

Create a category of UIImage class and add the following method

- (UIImage *)imageTintedWithColor:(UIColor *)color
{
     UIImage *image;
     if (color) {
        // Construct new image the same size as this one.
        UIGraphicsBeginImageContextWithOptions([self size], NO, 0.0); // 0.0 for scale means "scale for device's main screen".
        CGRect rect = CGRectZero;
        rect.size = [self size];

        // tint the image
        [self drawInRect:rect];
        [color set];
        UIRectFillUsingBlendMode(rect, kCGBlendModeScreen);

        // restore alpha channel
        [self drawInRect:rect blendMode:kCGBlendModeDestinationIn alpha:1.0f];

        image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    return image;
}

edited Sep 18 '15 at 13:39

eugen

85
2
6

answered Sep 30 '14 at 07:51

abhishekkharwar

3,529
2
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31

This code is changing the color of my white border only. The black fill remains as it is. I just want to change the black fill to other color. – Pria Sep 30 '14 at 08:01
Recreate your image may be there is some problem. You can open it in preview and resave it. – abhishekkharwar Sep 30 '14 at 08:10
2

That blend mode is the wrong one. Try changing kCGBlendModeMultiply to kCGBlendModeScreen. I think that will do it. – Christian Fox Sep 30 '14 at 08:19
Worked.. Changed the Blend Mode. Thanks @KristianFox :) – Pria Sep 30 '14 at 08:23
@abhishekkharwar - I will change the Blend mode in your code and accept the answer – Pria Sep 30 '14 at 08:24
I can still see a little color outside my white border also. Is there a way to get rid of that also? – Pria Sep 30 '14 at 08:26
Thanks @Pria, Can you please attach a screenshot hows is it looking? – abhishekkharwar Sep 30 '14 at 10:04
@abhishekkharwar - Have added the screenshot in the question. Plz check. – Pria Sep 30 '14 at 10:58
Is it possible to allow `color` be a colour with alpha that's not 1? – Liau Jian Jie Sep 10 '15 at 03:55
@LiauJianJie Yes that's possible try this [[UIColor greenColor] colorWithAlphaComponent:0.5f]; – abhishekkharwar Sep 10 '15 at 05:12
@abhishekkharwar i meant to say that is there a way to modify your snippet so that the black fill can be replaced by a translucent colour? – Liau Jian Jie Sep 10 '15 at 05:19
@LiauJianJie not sure did you try to change alpha value in [self drawInRect:rect blendMode:kCGBlendModeDestinationIn alpha:1.0f]; ? – abhishekkharwar Sep 10 '15 at 05:28
@abhishekkharwar yea i did, it just changes the alpha of the entire drawing. – Liau Jian Jie Sep 10 '15 at 07:57

iOS: Change black color in UIImage to another color

1 Answers1