UIImage Resize without quality loss

Question

I am looking for an external library (or a method using Apple frameworks that does not destroy quality) that will allow me to scale images.

I tried this “simple image processing library”, but it works only for black and white - I don’t know how to make it work for color images. ( http://code.google.com/p/simple-iphone-image-processing/ )

I tried Core Graphics, UIKit, the "trevor" method ( http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/ ), which makes EXTREMELY blurry images, and in fact, I don’t know what else I can do - I can’t continue to program my application without getting at least half-decent image scaling. I think interpolation is required to get decent results.

Given the recent advances in iOS, I really hope someone can help me. This is not a problem that only I encounter, many other people have the same problem, so if someone can solve it here, I’m sure that if it would be appreciated by a very wide audience!

Many thanks

Answer 1

My answer:

OK - the one who actually answered my question and then deleted their answer, I really don't know why.

Here are three different approaches:

• Using the Trevor Category approach - I think it's awful to keep it sharp. This is more useful if you are trying to prevent jagged lines from appearing.
• Using support for iOS5 Core Image and the AffineTransform filter - the more advanced CILanczosScaleTransform is not available in iOS (as far as I know). Actually, pretty bad results.
• Using the MGImageUtilities category - this seems to give excellent results while decreasing. ( https://github.com/mattgemmell/MGImageUtilities )

Here is a screenshot of four images. ENLARGE IT !: http://i.stack.imgur.com/M3DVE.jpg Left → Right: original, alarm, kernel image, MGIU.

Surprisingly, the picture on the right edge has about sixty times less memory use than the image on the left. Almost the same quality. On a small screen - always resize large images!