Application.CaptureScreenshot  

static function CaptureScreenshot (filename : String, superSize : int = 0) : void

Description

Captures a screenshot at path filename as a PNG file.

If the file exists already, it will be overwritten. This function does nothing if used from inside the web player.

When superSize parameter is larger than 1, a larger resolution screenshot will be produced. For example, passing 4 will make the screenshot be 4x4 larger than it normally would. This is useful to produce screenshots for printing.

function OnMouseDown() {
    Application.CaptureScreenshot("Screenshot.png");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnMouseDown() {
        Application.CaptureScreenshot("Screenshot.png");
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnMouseDown():
        Application.CaptureScreenshot('Screenshot.png')