Unityでお絵かき

UniPainter.cs

using UnityEngine;
using System;

public class UniPainter : MonoBehaviour {
    Texture2D texture;
  string color_str = "000000";

	void Start () {
		texture=guiTexture.texture as Texture2D;
		if (texture == null) {
			texture = new Texture2D(256,256);
			guiTexture.texture = texture;
		}
	}
	void OnGUI () {
		color_str= GUI.TextField(new Rect(0,0,100,20),color_str);
	}
	
	bool write = false;
	Vector3 beforeMousePos;
	void Update () {
		if (write) {
			Vector3 v=Input.mousePosition;
			lineTo(beforeMousePos, v, getColor());
			beforeMousePos = v;
			texture.Apply();
		}
	}
	
	public Color getColor() {
		try {
			float r = Convert.ToInt32(color_str.Substring(0, 2), 16);
			float g = Convert.ToInt32(color_str.Substring(2, 2), 16);
			float b = Convert.ToInt32(color_str.Substring(4, 2), 16);
			return new Color(r, g, b);
		} catch (Exception e) {
			return Color.black;	
		}
	}
	
	public void lineTo(Vector3 start, Vector3 end, Color color){
		float x = start.x, y = start.y;
		// color of pixels
		Color[] wcolor = {color};
		
		if (Mathf.Abs(start.x-end.x) >= Mathf.Abs(start.y-end.y)) {
				float dy = end.x == start.x ? 0 : (end.y-start.y) / (end.x-start.x);
				float dx = start.x < end.x ? 1 : -1;
			//draw line loop
				while (x >= 0 && x < texture.width && y >= 0 && y < texture.height) {
					try {
						texture.SetPixels((int)x,(int)y,1,1,wcolor);
						x+=dx;
						y+=dx*dy;
						if (start.x <= end.x && x >= end.x ||
							start.x >= end.x && x <= end.x) {
							break;	
						}
					} catch (Exception e) {
						Debug.LogException(e);
						break;
					}
				}
			} else if (Mathf.Abs(start.x-end.x) < Mathf.Abs(start.y-end.y)) {
				float dx = start.y == end.y ? 0 : (end.x-start.x) / (end.y-start.y);
				float dy = start.y < end.y?1:-1;
				while (x >= 0 && x < texture.width && y >= 0 && y < texture.height) {
					try {
						texture.SetPixels((int)x,(int)y,1,1,wcolor);
						x+=dx*dy;
						y+=dy;
						if (start.y <= end.y && y >= end.y ||
							start.y >= end.y && y <= end.y) {
							break;	
						}
					} catch (Exception e) {
						Debug.LogException(e);
						break;
					}
				}
			}
	}
	
	void OnMouseDown(){
		beforeMousePos = Input.mousePosition;
		write=true;
	}
	void OnMouseUp(){
		write=false;
	}
}