Unity: Adds a context menu option to RenderTextures that allows saving them to a file.

RenderTextureToFile.cs

public static class RenderTextureToFile
{
    	[UnityEditor.MenuItem("CONTEXT/RenderTexture/To Texture")]
	static void SaveRenderTextureToTexture(UnityEditor.MenuCommand command)
	{
		var rt = (RenderTexture)command.context;
		if (rt == null)
			return;

		// Ask for a save path.
		var path = UnityEditor.EditorUtility.SaveFilePanel("Save RenderTexture...", Application.dataPath, rt.name, "png");

		// Escape if user clicked cancel.
		if (path == "")
			return;

		// Set RenderTexture to one that will be read.
		RenderTexture.active = rt;

		// Create Texture2D of same size.
		// NOTE: If the TextureFormat of the Texture2D and the RenderTextureFormat of the RenderTexture aren't compatible, there will be an error. ARGB32 works for most cases though.
		var tex = new Texture2D(rt.width, rt.height, TextureFormat.ARGB32, false);
		tex.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0);
		tex.Apply();

		// Set to null so the RenderTexture won't accidentally be drawn to somewhere else.
		RenderTexture.active = null;

		// Encode to PNG.
		var bytes = tex.EncodeToPNG();

		// Write to file.
		System.IO.File.WriteAllBytes(path, bytes);
	}
}