GIMP Pixel Problem

[Larb]

The type of file you save your image as has an effect on what information it stores and what quality the end result is.

It sounds like you are working on an image, then saving it as a .jpg file. This is a "flat" compressed image file suitable for viewing on the web. The compression process results in a loss of quality - specifically the transitional area between colours and edges. It goes all weird close up (it is sometimes referred to as "jpg artifacting").

Basically you shouldn't use .jpg for a work-in-progress image.

If you are working between MS Paint and GIMP then I suggest saving your work-in-progress image as a TIFF file (.tif) or a bitmap (.bmp). You'll have the option to do that when you go to "save as". Only save your final ready image as a jpg if you intend to upload it somewhere. And keep a backup of your work-in-progress version so you always have a higher quality original should you ever need it.

Also! I'd suggest digging up some beginner GIMP tutorials on youtube or the web or wherever. I don't know what ones to recommend as I use photoshop myself but they will be really useful for getting to grips with the basics and it's stuff you'll pick up much quicker than you might think. Perhaps someone else can suggest some good ones.