How to create billboard version of a tree?

I've modified the first c# codes and is currently working with Unity 5.5.0f3. My changes are commented with //**. Important: For this to work you must not have any skybox. Go to Window>>Lighting>>Scene>>Skybox and set it to none!

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Script_Billboard_Create : MonoBehaviour {
 
     /*
 Make a billboard out of an object in the scene
 The camera will auto-place to get the best view of the object so no need for camera adjustment
 
 To use - place an object in an empty scene with just camera and any lighting you want.
 Add this script to your scene camera and link to the object you want to render.
 Press play and you will get a snapshot of the object (looking down the +Z-axis at it) saved out to billboard.png in your project folder
 Any pixels colored the same as the camera background color will be transparent
 */
 
     
     public GameObject objectToRender;
     public int imageWidth = 128;
     public int imageHeight = 128;
     //**bool to only conver once
     private bool grab = false;
 
     void Start()
     {
         CameraSetup();
     }
 
     void OnPostRender()
     {
         if (!grab) { ConvertToImage(); grab = true; }
     }
 
     //**split into two methods
     void CameraSetup()
     {
         //grab the main camera and mess with it for rendering the object - make sure orthographic
         Camera cam = Camera.main;
         cam.orthographic = true;
 
         //render to screen rect area equal to out image size
         float rw = imageWidth;
         rw /= Screen.width;
         float rh = imageHeight;
         rh /= Screen.height;
         cam.rect = new Rect(0, 0, rw, rh);
         //**manually set the background color
         cam.backgroundColor = new Vector4(0,0,0,0);
 
         //grab size of object to render - place/size camera to fit
         Bounds bb = objectToRender.GetComponent<Renderer>().bounds;
 
         //place camera looking at centre of object - and backwards down the z-axis from it
         cam.transform.position = bb.center;
         cam.transform.position.Set(cam.transform.position.x, cam.transform.position.y, -1.0f + (bb.min.z * 2.0f));
         //make clip planes fairly optimal and enclose whole mesh
         cam.nearClipPlane = 0.5f;
         cam.farClipPlane = -cam.transform.position.z + 10.0f + bb.max.z;
         //set camera size to just cover entire mesh
         cam.orthographicSize = 1.01f * Mathf.Max((bb.max.y - bb.min.y) / 2.0f, (bb.max.x - bb.min.x) / 2.0f);
         cam.transform.position.Set(cam.transform.position.x, cam.orthographicSize * 0.05f, cam.transform.position.y);
     }
 
     void ConvertToImage()
     {
         var tex = new Texture2D(imageWidth, imageHeight);
         // Read screen contents into the texture
         tex.ReadPixels(new Rect(0, 0, imageWidth, imageHeight), 0, 0);
         tex.Apply();
 
         //turn all pixels == background-color to transparent
         Camera cam = Camera.main;
         Color bCol = cam.backgroundColor;
         Color alpha = new Vector4(0,0,0,0);
         alpha.a = 0.0f;
         for (int y = 0; y < imageHeight; y++)
         {
             for (int x = 0; x < imageWidth; x++)
             {
                 Color c = tex.GetPixel(x, y);
                 //**check for difference
                 if (c.r != bCol.r)
                     tex.SetPixel(x, y, new Vector4(c.r, c.g, c.b, 1));
             }
         }
         tex.Apply();
         
         // Encode texture into PNG
         byte[] bytes = tex.EncodeToPNG();
         Destroy(tex);
 
         //**path is in Assets, you must refresh Unity to see the file (can be done by clicking away then click on Unity window again, etc)
         System.IO.File.WriteAllBytes(Application.dataPath + "/billboard.png", bytes);
     }
 }

Interesting script, but not working for me in Unity 5 or 4.6 neither. The .js version found in another thread works... but with plain textures only (alpha is discarded, which makes it useless when you apply this to meshes using transparent textures.

But I found a workaround : change this single line as below :

if (c.r == bCol.r || c.a != 1)

(Last be sure to set up a camera looking in world z axis, and you'll find your png at the very root of your project folder)

 #pragma strict
 
 /* 
 Make a billboard out of an object in the scene 
 The camera will auto-place to get the best view of the object so no need for camera adjustment 
 
 To use - place an object in an empty scene with just camera and any lighting you want. 
 Add this script to your scene camera and link to the object you want to render. 
 Press play and you will get a snapshot of the object (looking down the +Z-axis at it) saved out to billboard.png in your project folder 
 Any pixels colored the same as the camera background color will be transparent 
 */ 
 
 var objectToRender : GameObject; 
 var imageWidth : int = 128; 
 var imageHeight : int = 128; 
 
 function Start() 
 { 
     if (!objectToRender) return; 
 
     //grab the main camera and mess with it for rendering the object - make sure orthographic 
     var cam : Camera = Camera.main; 
     cam.orthographic = true; 
      
     //render to screen rect area equal to out image size 
     var rw : float = imageWidth; rw /= Screen.width; 
     var rh : float = imageHeight; rh /= Screen.height; 
     cam.rect = Rect(0,0,rw,rh); 
      
     //grab size of object to render - place/size camera to fit 
     var bb : Bounds = objectToRender.GetComponent(Renderer).bounds; 
      
         //place camera looking at centre of object - and backwards down the z-axis from it 
     cam.transform.position = bb.center; 
     cam.transform.position.z = -1.0 + (bb.min.z * 2.0); 
         //make clip planes fairly optimal and enclose whole mesh 
     cam.nearClipPlane = 0.5; 
     cam.farClipPlane = -cam.transform.position.z + 10.0 + bb.max.z; 
         //set camera size to just cover entire mesh 
     cam.orthographicSize = 1.01 * Mathf.Max( (bb.max.y - bb.min.y)/2.0, (bb.max.x - bb.min.x)/2.0); 
     cam.transform.position.y += cam.orthographicSize * 0.05; 
 
     //render 
     yield new WaitForEndOfFrame(); 
      
     var tex = new Texture2D( imageWidth, imageHeight, TextureFormat.ARGB32, false ); 
     // Read screen contents into the texture 
     tex.ReadPixels( Rect(0, 0, imageWidth, imageHeight), 0, 0 ); 
     tex.Apply(); 
 
     //turn all pixels == background-color to transparent 
     var bCol : Color = cam.backgroundColor; 
     var alpha = bCol; 
     alpha.a = 0.0; 
     for(var y : int = 0; y < imageHeight; y++) 
     { 
         for(var x : int = 0; x < imageWidth; x++) 
         { 
             var c : Color = tex.GetPixel(x,y); 
             // if (c.r == bCol.r)
             if (c.r == bCol.r || c.a != 1) 
                 tex.SetPixel(x,y,alpha); 
         } 
     } 
     tex.Apply(); 
 
     // Encode texture into PNG 
     var bytes = tex.EncodeToPNG(); 
     Destroy( tex ); 
     System.IO.File.WriteAllBytes(Application.dataPath + "/../billboard.png", bytes);
     Debug.Log("tex saved!"); 
 }