UIImage resize with hard edges

Question

I need a method for resizing UIImage like in photoshop with "nearest neighbour" resampling. I was looking for some, but everything I found was about CoreGraphics thicks to improve bicubic resampling quality. I have pixel-style design in my app, and a lot of stuff I create by pixel and then enlarge it with x5 multiplier (and it takes a lot of time, so I even close to writing a script for Photoshop). For example:

>

But I really don't need this like result of resampling:

Maybe anyone will show me the right way.

Answer 1

When you draw your image into a graphics context, you can set the graphics context's interpolation quality to "none", like this (e.g. in a view's drawRect method):

CGContextRef c = UIGraphicsGetCurrentContext();
CGContextSetInterpolationQuality(c, kCGInterpolationNone);
UIImage *image = [UIImage imageNamed:@"pixels.png"];
[image drawInRect:self.bounds];

If you need the result as a UIImage (e.g. to assign it to a built-in UI control), you could do this with UIGraphicsBeginImageContext (you'll find lots of examples for that).

An alternative would be to set the magnificationFilter property of an image view's layer:

pixelatedImageView.layer.magnificationFilter = kCAFilterNearest;

This is probably faster and more memory-efficient, because you don't need to redraw the image.