Question

I am looking for a way to, in Objective-C, create a PNG from several smaller PNGs based on how the user sets things up. Is this possible using existing Apple classes, or do I need to use a 3rd party library? If 3rd party code is needed, can anyone recommend a good library? The simpler the better – simple filters (such as darkening/lightening the image) would be nice but not required.

Here is some pseudo-code, to give you a better idea of what I am looking for:

image = [myImageLibrary imageWithHeight:1024 width:768];
[image addImage:@"background.png" atX:0 andY:0 withRotation:0];
[image addImage:@"image2.png" atX:100 andY:200 withRotation:90];
[image saveAtLocation:@"output.png"];

At output.png we see image2.png placed on top of background.png and rotated 90 degrees

P.S. – I am sorry if this seems to be a duplicate of another question, I just have not found an answer that works for what I am trying to do.

Answer 1

Have you read the “Creating and Drawing Images” section of the Drawing and Printing Guide for iOS and the UIImage Class Reference docs?

What you’re after is perfectly possible – with a well built class you could pretty much use that pseudo code as-is.

As a starter for ten, you could:

1. Create your own graphics context via UIGraphicsBeginImageContext.
2. Draw into that via the drawAtPoint: method of the UIImage class
3. Save the resultant image data out via UIGraphicsGetImageFromCurrentImageContext.

In terms of steps 1 and 3, see the UIKit Function Reference for more info. Additionally, the imageWithCGImage:scale:orientation: method of the UIImage class may prove useful for performing transformations, etc. as a part of step 2.