This is a simple "whitepoint" correction plugin. It's ideal for images which have a slight color tint, and which contains some pixels which should be neutral grey. I wrote this plugin as my mobile camera usually ends up taking images with poor color balance, and I wanted a simple tool to correct it. I'm publishing it in case anyone else finds it useful. Usage: Select the Color Picker tool. Use the Color Picker to select a Primary Color which should be neutral grey.