Save png with text overlay

most would simply pay for an assett for something like this. but if you wanted to actually start coding something simple like this yourself you could put images of all the letters in the alphabet into an array and paste them onto your image.

here is a super simple working example to get you started:

     //drag and drop images of letters a through z into this first array in the inspector!!!
     //import setting of your images must have read/write eneabled for this to work
     //set texture type to advanced to show this setting
     public Texture2D[] AlphabetImages = new Texture2D[26];
     public string AZ = "abcdefghijklmnopqrstuvwxyz";
 
 
     //here is an example function that returns a texture with a string stamped on the bottom
     public Texture2D AddLetters(string say,Texture2D orig){
         say = say.ToLower ();
         Color clear = AlphabetImages [0].GetPixel (0, 0);
         int cur = 0;
         int push = 0;
         int i = 0;
         while (cur<say.Length) {
             i = AZ.IndexOf(say.Substring(cur,1));
             if(i>-1){
             int x = 0;
             while(x<AlphabetImages[i].width){
                 int y = 0;
                 while(y<AlphabetImages[i].height){
                     Color c = AlphabetImages[i].GetPixel(x,y);
                     if(c!=clear){orig.SetPixel(x+push,y,c);}
                     y++;}x++;}
                 push+=AlphabetImages[i].width;}
             cur++;}
         orig.Apply ();  return orig;}

 

if you have questions let me know!

I used a much easier way to do that, but it need to wait for one frame, and hold one layer.

1. create a RenderTexture

2. put it to a camera with its own layer

3. put all share content in front of this camera and set them to correct layer

4. if you have 2d elements, put it to a Canvas, set the render mode as "Screen space camera" or "world space"

5. i remember you can't call functions to force rendering ui. so your script need to use IEnumerator to wait one frame

6. create a Texture2D in your script, call ReadPixels to convert the RenderTexture's content to this Texture2D

7. share this Texture2D

EDIT for the sharing feature, you need to buy third part plugin. It saves you lots of time. There are lots of programming, testing, bug fixing if you want to make a share feature from sketch. I am using this one:

https://www.assetstore.unity3d.com/en/?stay#!/content/15066

A simple way might be to create a canvas or sprite with the image from file and a UI text or TextMeshPro text over it. Then save a screenshot using ScreenCapture.CaptureScreenshot() and crop/scale the png captured as appropriate.

Sure the image appears on the screen for a moment but this might not be a bad thing? It could be an framed image with a post to FB button under it.