What is best way to add transparent padding all around my sprites?

Questions & Answers
1

The shader I am working on requires that my sprites have a transparent padding all around them that corresponds to the largest dimension of the sprite.

ie.: If my sprite is 64px high by 32px wide, I need to add a 64px padding all around it

I was hoping to figure out a way to avoid having to add that padding ourselves within our image editing software.

Is there a way to do this inside a shader? I guess it could also be done within a C# script attached to our sprites but the idea here would be to NOT modify the source images.

Thank you for reading.

3

public Texture2D oldpic;
public Texture2D newpic;
int padsize;
int i;
int i2;
Color c;

	void Start () {
	

				// in the inpector click on your texture and go to the import setting. 
				// change the texture type to advanced and enable read/write for your texture

		padsize = 64;
		i = padsize * 2;
		//make a new empty texture 		a bit bigger than your first
		newpic = new Texture2D (oldpic.height + i, oldpic.width + i);


		//make a loop to paint our new image clear
		i = newpic.height;
        while (i>0) {i--;
			i2=newpic.width;
			while(i2>0){i2--;
				newpic.SetPixel(i2,i,Color.clear);
			}
				}
		newpic.Apply ();

		// copy all the pixels from the first texture into the middle of the new one!!

	
		i = oldpic.height;
		while (i>0) {i--;
			i2=oldpic.width;
			while(i2>0){i2--;
				c=oldpic.GetPixel(i2,i);
				newpic.SetPixel(i2+padsize,i+padsize,c);
			}
		}
		newpic.Apply ();


	}
2

use the following approach when samping the texture by the quad:

0.1 uv is 0%

0.9 uv is 100%

For example

vec2 respecifiedUV = (currentUV) / (0.8) + 0.1;
respecifiedUV = clamp(currentUV(currentUV, 0, 1);

if(respecifiedUV < vec2(0)  || respecifiedUV > vec2(1)){
make transparent
}
else {
sample texture with respecifiedUV
}

Anything below 0.1 either on x or y should be vec4(0,0,0,0) aka fully transparent color. Use switch() and mix() to avoid branching via if-else (they are very hard for GPUs)

However, if you want to have border “eat-up” edges of your image, then just skip “respecifying uvs” part, and just use if-else or switch and mix