1.7. Image Arithmetic in AstroImageJ

AstroImageJ can do basic arithmetic with images: add, subtract, multiply, and divide them. To do arithmetic, go to the Process menu, and select either Image Calculator or Image/stack calculator (which you select depends on whether there is the toolbar or an image is on top).

Warning

Always have AstroImageJ display the result in a new window; you want to be sure to avoid accidentally overwriting or modifying the original data.

Let’s try a couple things to make sure you understand what the image calculator does.

Todo

1. Imagine subtracting an image from itself. What should the result be? Use AstroImageJ to subtract an image from itself. Does the result match your expectaion?
2. Imagine dividing an image by itself. What should the result be? Use AstroImageJ to divide an image by itself. Does the result match your expectation.