Generate a gradient texture from editor script

Hi does somebody know how to generate a gradient PNG from a editor script? Whats the formula behind it?

I've looked around but nothing worked :/

This generates a texture using UnityEngine; using System.Collections; using UnityEditor; using System.IO;

 public class GenGradient : EditorWindow {
     public Color fromm;
     public Color too;
     public float tt;
     [MenuItem ("Window/Gen Texture")]
     // Use this for initialization
     static void Init(){
         GenGradient window = (GenGradient)EditorWindow.GetWindow(typeof(GenGradient));
         window.maxSize = new Vector2(300,200);
     }
     void OnGUI(){
         if(GUILayout.Button("Gen")){
             GenTexture();
         }
         fromm = EditorGUILayout.ColorField(fromm);
         too = EditorGUILayout.ColorField(too);
         tt = EditorGUILayout.Slider(tt,0,100);
     }
     void GenTexture(){
         Texture2D texture = new Texture2D(64,64,TextureFormat.RGB24,false);
         Color[] colors = new Color[texture.width];
         for(int i = 0; i < texture.width; i++){
             //for(int y = 0; y <texture.height; y++){
                 colors[i].r = (i/225)*1000;//Linear((i/64)*100);
                 Debug.Log("Value"+(i/225f)*1000f);//Linear((i/64)*100));
                 texture.SetPixel(i,1,colors[i]);
             //}
         }
         texture.Apply();
         var bytes = texture.EncodeToPNG();
         File.WriteAllBytes("Assets/gui/swag.png",bytes);
         //AssetDatabase.CreateAsset(bytes,"Assets/hi.png");
         //AssetDatabase.CreateAsset(bytes,"Assets/grad.png");
         AssetDatabase.Refresh();
     }
     public float Linear (float per) {
         return fromm.r * per + too.r * (1-per);
     }
 }