unity 框选自由截屏

using UnityEngine;
using System.Collections;
using System.IO;

public class draw : MonoBehaviour {
public Color rColor = Color.green;
private Vector3 start = Vector3.zero;
private Vector3 end = Vector3.zero;
private Material rMat = null;
private bool drawFlag = false;
private Rect rect;
private Texture2D cutImage;
// Use this for initialization
void Start () {
rMat =  new Material( "Shader \"Lines/Colored Blended\" {" +
"SubShader { Pass { " +
"    Blend SrcAlpha OneMinusSrcAlpha " +
"    ZWrite Off Cull Off Fog { Mode Off } " +
"    BindChannels {" +
"      Bind \"vertex\", vertex Bind \"color\", color }" +
"} } }" );//生成画线的材质
rMat.hideFlags = HideFlags.HideAndDontSave;
rMat.shader.hideFlags = HideFlags.HideAndDontSave;
}

// Update is called once per frame
void Update () {
if(Input.GetMouseButtonDown(0)){
drawFlag = true;//如果鼠标左键按下 设置开始画线标志
start = Input.mousePosition;//记录按下位置
end = Input.mousePosition;//鼠标当前位置
}else if (Input.GetMouseButtonUp(0)){
drawFlag = false;//如果鼠标左键放开 结束画线

}
if (Input.GetKeyDown (KeyCode.P)) {
StartCoroutine(CutImage());
}
}
//绘制框选
void OnPostRender() {//画线这种操作推荐在OnPostRender（）里进行 而不是直接放在Update，所以需要标志来开启
if(drawFlag){
end = Input.mousePosition;//鼠标当前位置
}
GL.PushMatrix();//保存摄像机变换矩阵

if (! rMat)
return;

rMat.SetPass( 0 );
GL.LoadPixelMatrix();//设置用屏幕坐标绘图
GL.Begin(GL.QUADS);
GL.Color( new Color(rColor.r,rColor.g,rColor.b,0.1f) );//设置颜色和透明度，方框内部透明
GL.Vertex3( start.x,start.y,0);
GL.Vertex3( end.x,start.y,0);
GL.Vertex3( end.x,end.y,0 );
GL.Vertex3( start.x,end.y,0 );
GL.End();
GL.Begin(GL.LINES);
GL.Color(rColor);//设置方框的边框颜色 边框不透明
GL.Vertex3( start.x,start.y,0);
GL.Vertex3( end.x,start.y,0);
GL.Vertex3( end.x,start.y,0);
GL.Vertex3( end.x,end.y,0 );
GL.Vertex3( end.x,end.y,0 );
GL.Vertex3( start.x,end.y,0 );
GL.Vertex3( start.x,end.y,0 );
GL.Vertex3(start.x,start.y,0);
GL.End();
GL.PopMatrix();//恢复摄像机投影矩阵

}

IEnumerator CutImage()
{

string date = System.DateTime.Now.ToString("yyyyMMddHHmmss");
//图片大小
cutImage = new Texture2D((int)(end.x - start.x), (int)(start.y - end.y), TextureFormat.RGB24, true);

//坐标左下角为0
rect = new Rect((int)start.x, Screen.height - (int)(Screen.height - end.y), (int)(end.x - start.x), (int)(start.y - end.y));

yield return new WaitForEndOfFrame();
cutImage.ReadPixels(rect, 0, 0, true);

cutImage.Apply();
yield return cutImage;
byte[] byt = cutImage.EncodeToPNG();
//保存截图
File.WriteAllBytes(Application.streamingAssetsPath + "/CutImage" +date + ".png", byt);

}

}

<span style="white-space:pre">			</span>GL.LoadPixelMatrix();//设置用屏幕坐标绘图
GL.Begin(GL.QUADS);
GL.Color( new Color(rColor.r,rColor.g,rColor.b,0.1f) );//设置颜色和透明度，方框内部透明
GL.Vertex3( start.x,start.y,0);
GL.Vertex3( end.x,start.y,0);
GL.Vertex3( end.x,end.y,0 );
GL.Vertex3( start.x,end.y,0 );
GL.End();