I can use shaders/effects to render 3D objects, but I now want to use them to edit textures only. i.e. I want to create a shader which will take a texture as an input, apply an effect to it (for example, monochrome, blur, etc...) and will then output the final result as another texture. Are there any good tutorials on how to use shaders like this?
I should also say that I'm not looking to render the texture to the screen, I just want to apply an effect to it so that I can then sample it in my main shader.