Resizing an image with stretchableImageWithLeftCapWidth

Question

I\'m trying to resize an image using stretchableImageWithLeftCapWidth: it works on the simulator, but on the device, vertical green bars appears.

I\'ve tried to use

Answer 1

I've spent 5 hours debugging this last night, disabling PNG compression in xcode didn't do anything for me.

For anyone else meeting vertical, green, bars/lines/artifacts with stretchableImageWithLeftCapWidth (in UIImage API) - this post is for you.

I have a 21x30 for a custom barbutton background that I want to widen, but got the same green stripes as the OP. I found a PNG created with photoshop and that worked fine - mine are made with Gimp. Anyway, stripping ALL chunks from the files (except the three essential ones) made no difference. Neither did disabling PNG compression.

What did work for me was this:

1. Add ONE empty line above my image (which is now 21x31).
2. Set topCapHeight:0 when creating the scaled image.
3. When I use my scaled image, I draw into a CGContext, which is later used to make an UIImage. I use this to draw: [image drawInRect:CGRectMake(0,-2,width,32)];

This makes the problem go away (for me).

I assume that the bug/issue has to do with not scaling vertically when drawing, so I force scaling of the first source image line (into two lines), which are draw outside my composition.

I hope this helps someone save 5 hours.

/Krisb