RenderTextureExtensions.cs

using UnityEngine;
using System.IO;
using System;

public static class RenderTextureExtensions
{

	private static DefaultDictionary<RenderTexture, Texture2D> _cachedTextures = new DefaultDictionary<RenderTexture, Texture2D>();


	public static Texture2D GetTexture(this RenderTexture renderTexture)
	{
		var tex = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.ARGB32, false);
		_cachedTextures[renderTexture] = tex;
		var prevRenderTexture = RenderTexture.active;
		RenderTexture.active = renderTexture;
		tex.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
		tex.Apply();
		RenderTexture.active = prevRenderTexture;
		return tex;
	}

	public static Texture2D GetTextureRGBA32(this RenderTexture renderTexture)
	{
		var tex = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.RGBA32, false);
		_cachedTextures[renderTexture] = tex;
		var prevRenderTexture = RenderTexture.active;
		RenderTexture.active = renderTexture;
		tex.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
		tex.Apply();
		RenderTexture.active = prevRenderTexture;
		return tex;
	}

	public static Texture2D GetTextureWithoutAlpha(this RenderTexture renderTexture)
	{
		var tex = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.RGB24, false);
		_cachedTextures[renderTexture] = tex;
		RenderTexture.active = renderTexture;
		tex.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
		tex.Apply();
		return tex;
	}

	public static void SaveAs(this RenderTexture renderTexture, string fileName)
	{

		if (renderTexture.format != RenderTextureFormat.ARGB32) throw new ArgumentException("The format for the render texture must be ARGB32.");

		// convert to a texture
		Texture2D tex = _cachedTextures[renderTexture];
		if (tex == null) tex = renderTexture.GetTexture();
		else
		{
			var prevRenderTexture = RenderTexture.active;
			RenderTexture.active = renderTexture;
			tex.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
			tex.Apply();
			RenderTexture.active = prevRenderTexture;
		}

		// save the texture
		tex.SaveAs(fileName);
		//GameObject.Destroy(tex);
	}

	public static byte[] EncodeAsImage(this Texture2D tex, string fileName)
	{
		byte[] bytes = null;
		if (fileName.ToLower().EndsWith("png")) bytes = tex.EncodeToPNG();
		else if (fileName.ToLower().EndsWith("jpg") || fileName.ToLower().EndsWith("jpeg")) bytes = tex.EncodeToJPG(90);
		else throw new ArgumentException("File DisplayName with extension " + fileName + " not supported. Please use png or jpg.");
		return bytes;
	}

	public static void SaveAs(this Texture2D tex, string fileName)
	{
		var bytes = EncodeAsImage(tex, fileName);
		string dir = Path.GetDirectoryName(fileName);
		if (!string.IsNullOrEmpty(dir) && !Directory.Exists(dir)) PathExt.EnsureDirectory(dir);
		File.WriteAllBytes(fileName, bytes);
	}

	public static void SaveAsWithMaximumFileSize(this Texture2D tex, string fileName, int maxFileSizeInBytes, int startQuality = 95)
	{
		byte[] bytes = null;
		if (fileName.ToLower().EndsWith("png"))
		{
			bytes = tex.EncodeToPNG();
			if (bytes.Length > maxFileSizeInBytes) throw new ArgumentException($"Cannot compress the texture into a PNG of size {maxFileSizeInBytes}, compressed size is {bytes.Length}.");
		}
		else if (fileName.ToLower().EndsWith("jpg") || fileName.ToLower().EndsWith("jpeg"))
		{
			int quality = startQuality;
			while (quality > 0)
			{
				bytes = tex.EncodeToJPG(quality);
				if (bytes.Length <= maxFileSizeInBytes) break;
				else quality -= 5;
			}
			if (quality == 0) throw new ArgumentException($"Failed to compress image to JPEG: even the lowest quality setting compresses to {bytes.Length}, which is more than the required {maxFileSizeInBytes}.");
		}
		else throw new ArgumentException("File DisplayName with extension " + fileName + " not supported. Please use png or jpg.");
		string dir = Path.GetDirectoryName(fileName);
		if (!string.IsNullOrEmpty(dir) && !Directory.Exists(dir)) PathExt.EnsureDirectory(dir);
		File.WriteAllBytes(fileName, bytes);
	}
}