Code Snippet: Size RawImage to Parent, keep aspect ratio.

Here's a handy little script I came up with, so you can tell any RawImage to fill it's parent's Rect, while maintaining the aspect ratio of the src texture. It also supports %-based padding, and images that have been rotated by 90 degree increments.

Code (csharp):

1.  
2. static class CanvasExtensions {
3.     public static Vector2 SizeToParent(this RawImage image, float padding = 0) {
4.         var parent = image.transform.parent.GetComponent<RectTransform>();
5.         var imageTransform = image.GetComponent<RectTransform>();
6.         if (!parent) { return imageTransform.sizeDelta; } //if we don't have a parent, just return our current width;
7.         padding = 1 - padding;
8.         float w = 0, h = 0;
9.         float ratio = image.texture.width / (float)image.texture.height;
10.         var bounds = new Rect(0, 0, parent.rect.width, parent.rect.height);
11.         if (Mathf.RoundToInt(imageTransform.eulerAngles.z) % 180 == 90) {
12.               //Invert the bounds if the image is rotated
13.               bounds.size = new Vector2(bounds.height, bounds.width);
14.         }
15.         //Size by height first
16.         h = bounds.height * padding;
17.         w = h * ratio;
18.         if (w > bounds.width * padding) { //If it doesn't fit, fallback to width;
19.             w = bounds.width * padding;
20.             h = w / ratio;
21.         }
22.         imageTransform.sizeDelta = new Vector2(w, h);
23.         return imageTransform.sizeDelta;
24.     }
25. }
26.  

Usage:

Code (csharp):

1. rawImage.SizeToParent();

This is mostly useful for when you're loading a bunch of external images into a container, w/ random aspect ratios, and want them to fill the available space, without losing aspect ratio. The Image control is has a similar API, but requires you create a new Sprite() everytime you swap textures, which is a major performance drain.

 

Thank you for sharing, this saved me some time ;-)
I did make some adjustments, enjoy !

Code (CSharp):

1.    
2. public static Vector2 SizeToParent(this RawImage image, float padding = 0) {
3.         float w = 0, h = 0;
4.         var parent = image.GetComponentInParent<RectTransform>();
5.         var imageTransform = image.GetComponent<RectTransform>();
6.  
7.         // check if there is something to do
8.         if (image.texture != null) {
9.             if (!parent) { return imageTransform.sizeDelta; } //if we don't have a parent, just return our current width;
10.             padding = 1 - padding;
11.             float ratio = image.texture.width / (float)image.texture.height;
12.             var bounds = new Rect(0, 0, parent.rect.width, parent.rect.height);
13.             if (Mathf.RoundToInt(imageTransform.eulerAngles.z) % 180 == 90) {
14.                 //Invert the bounds if the image is rotated
15.                 bounds.size = new Vector2(bounds.height, bounds.width);
16.             }
17.             //Size by height first
18.             h = bounds.height * padding;
19.             w = h * ratio;
20.             if (w > bounds.width * padding) { //If it doesn't fit, fallback to width;
21.                 w = bounds.width * padding;
22.                 h = w / ratio;
23.             }
24.         }
25.         imageTransform.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, w);
26.         imageTransform.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, h);
27.         return imageTransform.sizeDelta;
28.     }
29.  

 

Have tried this in various ways but I keep getting null reference on line: 4?

 

var parent = image.transform.parent.GetComponentInParent<RectTransform>();

Is the raw Image parented to an object with a recttransform?

 

DOH!!!! had script attached to wrong GO....!

 

works like a charm, Thanks!

 

Hey, thanks for this code. Its very useful, however, I think I found a bug.

GetComponentInParent() returns a component on this game object or its parents. So, in my case it was returning the RectTransform of the image itself instead of the parent rect. Super annoying. Here's the documentation:
https://docs.unity3d.com/ScriptReference/GameObject.GetComponentInParent.html

A fix - change line 3 to...

Code (CSharp):

1. var parent = image.transform.parent.GetComponent<RectTransform>();

 

I really appreciate it!!! Works flawlessly

 

Fixed. Better late than never

 

make sure ur RawImage RectTransform is not Stretched in the Editor.

 

This was so helpful thankyou!

 

I attached the component "Aspect Ratio Fitter" to the "Raw Image", and set "Width Controls Height" or "Height controls Width" according to the aspect ratio you want (depending if the raw image is expected to stretch horizontally or vertically). Worked for me, its definitely easier, though I dont know if more efficient. Just in case it might help someone, or to maybe look into it.

 

didn't work for video.
but maybe for images it should work