how to use [UIImage resizableImageWithCapInsets:]

Question

I'd like to stretch a image with size 170x50 and show it in an image view with size 240x140. The original image looks like:

I want to keep the four corners and only stretch the center part. I use the following code:

    UIImage *originalImg = [UIImage imageNamed:@"ImageNamed"];
    UIImage *resizeImg = [originalImg resizableImageWithCapInsets:UIEdgeInsetsMake(20 ,10, 10, 10)];
    self.originalImgV.image = originalImg;
    self.resizedImgV.image = resizeImg;

Both originalImgV and resizedImgV are set to "aspect fill". I run it on the simulater, and the result is :

What I can't understand is: the resizedImgV has 2 arrows! Could any one tell me why and how can I use it correctly? Thanks

Answer 1

Your issue is with the values you pass to UIEdgeInsetsMake. The values are top, left, bottom, right. Due to the arrow in the top left, you need to make sure your left value is big enough to go from the left edge of the image to just to the right of the arrow.

Given the image you posted, you want something like:

 UIEdgeInsetsMake(12, 32, 4, 4)

BTW - the image should only be left + right + 1 pixels wide and top + bottom + 1 pixels tall. So your image doesn't need to be nearly as big as it is.