How To draw Line by DrawTexture method?

I used this Script to draw lines but I can see nothing on the screen and there are no issues appeared:

     function Line (tex : Texture2D, x0 : int, y0 : int, x1 : int, y1 : int, col : Color) {
 var dy = y1-y0;
 var dx = x1-x0;
 
 if (dy < 0) {dy = -dy; var stepy = -1;}
 else {stepy = 1;}
 if (dx < 0) {dx = -dx; var stepx = -1;}
 else {stepx = 1;}
 dy <<= 1;
 dx <<= 1;
 
 tex.SetPixel(x0, y0, col);
 if (dx > dy) {
     var fraction = dy - (dx >> 1);
     while (x0 != x1) {
         if (fraction >= 0) {
             y0 += stepy;
             fraction -= dx;
         }
         x0 += stepx;
         fraction += dy;
         tex.SetPixel(x0, y0, col);
     }
 }
 else {
     fraction = dx - (dy >> 1);
     while (y0 != y1) {
         if (fraction >= 0) {
             x0 += stepx;
             fraction -= dy;
         }
         y0 += stepy;
         fraction += dx;
         tex.SetPixel(x0, y0, col);
     }
 }
     }

and this is the function call

     function Start () {
     var tex = new Texture2D (128, 128, TextureFormat.Alpha8, false);
     GetComponent.<Renderer>().material.mainTexture = tex;
         for (var i = 0; i < lines; i++)
             {
     Line(tex, Random.Range(0, texSize), 
     Random.Range(0, texSize), 
     Random.Range(0, texSize),
     Random.Range(0, texSize),
         Color(Random.Range(0.25, 1.0), 
         Random.Range(0.25, 1.0), 
         Random.Range(0.25, 1.0)) );
         }
 tex.Apply();
 GetComponent.<Renderer>().material.mainTexture = tex;
 }