Canvasthing

Canvasthing is an artist assistant app for working from reference images. It helps you plan a physical canvas by locking in your exact dimensions. You can add custom grids to map out the scale, generate a clean sketch outline to trace, or simplify complex details into basic color blocks so it's easier to paint. It also has a color inspector for mixing paint by eye. It's entirely free, has no ads, and doesn't require an account, just use it in your browser or install it.