Screenshooter.cs

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

// Attach this script to a camera.
public class Screenshooter : MonoBehaviour {

	int imgNumber;
	public int upscale = 2;

	void Start () {
		// Get the last screenshot number.
	 	if (File.Exists(@"E:\screenshot.txt")){
	 		string text = System.IO.File.ReadAllText(@"E:\screenshot.txt");
	 		imgNumber = int.Parse(text);
	 	}
		else{
			imgNumber = 0;
		}
	}

	void LateUpdate () {
		takeScreenshot ();
	}

	void takeScreenshot(){
		if (Input.GetKeyDown (KeyCode.K)) {
			imgNumber++;
			string path = @"Assets/Screenshots/screenshot" + imgNumber + ".png";
			Application.CaptureScreenshot (path, upscale);
			Debug.Log ("Screenshot " + imgNumber.ToString() + " taken");

			// Write to the text file.
			System.IO.File.WriteAllText (@"E:\screenshot.txt", imgNumber.ToString());
		}
	}
}