Make sure to allow Scratch to use your camera first. Press space to take a picture, and hold still for several minutes. The pictures are not saved to anywhere. No one besides you can see it. Right-click the canvas and select "Save image as..." to save your image.
For faster version: https://turbowarp.org/409977690?stuck Instant pixels version: https://scratch.mit.edu/projects/424751563/ Unshared by accident. This project has been out for almost a year now. Shared 6/5/20 Unshared/Reshared 5/21/20 This was based off of my image processing project. Credit to @griffpatch for the square-drawing code, and credit to @DadOfMrLog for the color detection code.