Analyze earthworms courses?

Dear community,
I have a picture with earthworms gears. i need the right macros to get this picture in 3 diffrent picture resolutions.After that i want to measure the earthworm gear sizes. It is my first contact with this program.i can handle the part with the measurements.
I would be very grateful for help.
with

What do you mean by “get this picture in 3 different resolutions”?

i mean three different picture resolution.
first picture with a half resolution of the original .
second picture with a quartel resolution of the original.
the last picture with a eighth resolution of the original.
thanks for the response.