Merge two UIImages

Question

I have imageA (taken from the users iPhone camera) and imageB, an image with a silly boarder (for eg) with plenty of transparent alpha space.

What I would like to to do is to merge these two images, laying imageB over imageA, and then saving them as imageC for other work.

Is there a way to do this?

Cheers

I've got this so far

-(void)merge
{
    CGSize size = CGSizeMake(320, 480);
    UIGraphicsBeginImageContext(size);

    CGPoint thumbPoint = CGPointMake(0,0);
    UIImage *imageA = imageView.image;
    [imageA drawAtPoint:thumbPoint];

    UIImage* starred = [UIImage imageNamed:@"imageB.png"];

    CGPoint starredPoint = CGPointMake(0, 0);
    [starred drawAtPoint:starredPoint];

    UIImage *imageC = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    imageView.image = imageC;
}

I can't see/dont know what I'm doing wrong here

Love the simplicity on this one. – Eric Brotto Aug 21 '12 at 11:11 — Eric Brotto, Aug 21 '12 at 11:11

score 3 · Answer 1 · answered Jul 03 '12 at 12:43

3

Note that for retina support you should use: UIGraphicsBeginImageContextWithOptions(size, YES, 0); // 0 means let iOS deal with scale for you

answered Jul 03 '12 at 12:43

Geva

820
6
14

score 3 · Accepted Answer · answered Dec 07 '10 at 08:09

3

That code looks correct (though I would recommend converting it to use a created CGBitmapContext for thread-safety), but is imageB supposed to be a JPEG? JPEGs don't support transparency, so, in order for the blending to work, it should really be a PNG.

answered Dec 07 '10 at 08:09

Justin Spahr-Summers

16,893
2
61
79

was mean to be a png, no difference though. – Sam Jarman Dec 07 '10 at 08:30
ah it was the location of the code that did it - turns out imageView.image was nil. – Sam Jarman Dec 07 '10 at 22:56

Merge two UIImages

2 Answers2

Linked