Export RenderTexture to a file

RenderTextureUtils.cs

using System;
using UnityEditor;
using UnityEngine;

public static class RenderTextureUtils {
	public static TextureFormat DEFAULT_TEXTURE_FORMAT = TextureFormat.RGBA64;
	public static String DEFAULT_FILE_FORMAT = "png";
	
	/// <summary>
	/// Export a RenderTexture asset to a file
	/// </summary>
	/// <param name="renderTexture">The RenderTexture asset to export</param>
	/// <param name="filePath">The path the file should be located when saved</param>
	/// <exception cref="ArgumentException"></exception>
	public static void ExportRenderTexture(RenderTexture renderTexture, String filePath) {
		if (renderTexture == null) {
			throw new ArgumentException("RenderTexture value is null");
		}
		
		if (filePath == "") {
			throw new ArgumentException("FilePath value is non-valid, empty string");
		}
		
		// infer the file format from the file extension
		String fileExtension = filePath.Substring(filePath.LastIndexOf('.') + 1).ToLower();

		// transfer image from rendertexture to regular texture
		Texture2D texture = new Texture2D(renderTexture.width, renderTexture.height, DEFAULT_TEXTURE_FORMAT, false);
		
		RenderTexture.active = renderTexture;
		texture.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
		texture.Apply();

		// write texture to file
		byte[] imageBytes;
		
		switch (fileExtension) {
			case "png":
				imageBytes = texture.EncodeToPNG();
				break;
			case "jpg":
				imageBytes = texture.EncodeToJPG();
				break;
			case "exr":
				imageBytes = texture.EncodeToEXR();
				break;
			case "tga":
				imageBytes = texture.EncodeToTGA();
				break;
			default:
				throw new ArgumentException($"Invalid file extension: {fileExtension}");
		}
		
		System.IO.File.WriteAllBytes(filePath, imageBytes);
	}
	
#if UNITY_EDITOR
	
	public static String DEFAULT_FILE_NAME = "RenderTexture";
	
	[MenuItem("Assets/RenderTexture/Export currently selected")]
	private static void ExportRenderTexture() {
		RenderTexture renderTexture = Selection.activeObject as RenderTexture;
		
		String filePath = EditorUtility.SaveFilePanel(
			"Export RenderTexture", 
			"", renderTexture?.name ?? DEFAULT_FILE_NAME, 
			DEFAULT_FILE_FORMAT);
		
		ExportRenderTexture(renderTexture, filePath);
	}
	
#endif
}