ScreenshotHelper.cs

using UnityEditor;
using UnityEngine;

/// <summary>
/// Made by Rodrigo Diaz
/// http://www.rodrigos.work
/// This code is licensed under MIT license
/// 
/// Make sure to add this class under a folder named "Editor" in the Unity Project
/// 
/// Instructions: Either go to Edit/Screencapture or press alt-c to take the screenshot.
/// It only works if you have the Game window open in the editor.
/// 
/// </summary>
public class ScreenshotHelper
{
	private static string path;

	[MenuItem("Edit/Screencapture &c")]
	public static void Screencapture()
	{
		if (Camera.main) {
			if (string.IsNullOrEmpty(path)) {
				path = EditorUtility.SaveFilePanel("Save png", path, "screenshot.png", "png");
			}

			if (path.Length != 0) {
				ScreenCapture.CaptureScreenshot(path);
			}
		} else {
			EditorUtility.DisplayDialog("No Camera in the scene", "Camera not found in the scene, please add one", "OK");
		}
	}

	[MenuItem("Edit/Screencapture save as ^&c")]
	public static void ScreenShotSaveAs()
	{
		path = null;
		Screencapture();
	}
}