SKTexture Regular Rect Coordinates Subtexture

Use regular CGRect coordinates to get subtextures from SKTexture in Sprite Kit code. This was made using Objective C categories.

Why this?

I was playing a bit with SKTexture and the method

+ (SKTexture *)textureWithRect:(CGRect)rect inTexture:(SKTexture *)texture

and I did not get the results as I expected. Then I went to see details about that method in the documentation and there was this part about the "rect" argument:

A rectangle in the unit coordinate space that specifies the portion of the texture to use.

So as you see, you need to use unit coordinate space coordinates. In most of methods that I used CGRect I used regular CGRect, example: (30, 20, 100, 300). That is why I made this SKTexture category. There are two methods added to SKTexture.

Methods

I added two methods to SKTexture using Objective C categories

First method returns CGRect in unit coordinates from CGRect in regular coordinates

+ (CGRect)unitRectFromRegularRect:(CGRect)rect inTexture:(SKTexture *)texture;

Second method returns SKTexture subtexture from texture using regular CGRect

+ (SKTexture *)textureWithRegularRect:(CGRect)rect inTexture:(SKTexture *)texture;

Examples

If you have some texture with dimensions 100x50 and you want to get subtexture from (10,20) with width of 40 and height of 30, you should call it like this:

CGRect regularRect = CGRectMake(10, 20, 40, 30);
//your SKTexture is loaded to "yourTexture" variable
SKTexture *subTexture = [SKTexture textureWithRegularRect:regularRect inTexture:yourTexture];

And this code will calculate your regular CGRect to unit coordinate space and return you the correct subtexture.

Method Arguments

You can pass CGRect of any values. If any of width or height is negative you will get back CGRect (0,0,0,0) or subtexture with that CGRect. If you have negative x or y in CGRect, values will be translated to 0 and width or height will also be changed. For example:

CGRect regularRect = CGRectMake(-10, 20, 50, 30);
//your SKTexture is loaded to "yourTexture" variable
SKTexture *subTexture = [SKTexture textureWithRegularRect:regularRect inTexture:yourTexture];

is the same as:

CGRect regularRect = CGRectMake(0, 20, 40, 30);
//your SKTexture is loaded to "yourTexture" variable
SKTexture *subTexture = [SKTexture textureWithRegularRect:regularRect inTexture:yourTexture];

You

I hope this will help you as well as it did to me :)