That's pointless, especially for a computer programmer or other engineer.
Using a spreadsheet like editing interface isn't a good solution to image processing with absolute control. Images are generally not edited pixel for pixel independently, which is what that abstraction would suggest. Messing with abstraction levels is a very bad practice in software. Not even the ordinary anti-aliased drawing tool works at the pixel level since the anti-aliasing usually implies altering several pixels adjacent to the dot (Note an anti-aliased dots need not to be located on a pixel dead center, they can be meaningfully placed at an arbitrary intermediate point between them).
To perform processing not already implemented in the relevant software a programmer can write an ad-hoc non interactive program that does what its required for the image and then finishes. Then, the actual editing process consists of the editing of the ad-hoc program or its parameters rather than interaction with a running copy of a generic image manipulation program through a graphical user interface. Note the ad-hoc program need not to be stand alone; it may be a script for a generic image manipulation program.
The GIMP is scriptable in
Scheme for instance.
For instance, the user may wish to apply a median filter where pixel values are weighted according to a Gaussian curve in the space domain. He may write a computer program to do so, with a CLI that accepts σ as the parameter which reads the input image from stdin in PPM format and writes it to stdout in PPM format as well. The equivalent to sliding a "σ" or "Radius" slider in a fully fledged editor having this feature would correspond to running the program with a different argument and visualizing the result.
This practice is nothing new by the way. Simple image manipulation programs can be a good way to experience computer programming. I think that knowing at least the basics of computer programming is very enriching for the intellect. Computer programming requires, and hence develops a way of thinking a class a part of what's used on almost everything else besides mathematics, to which related. Hence, if you have interest in computer programming/computer science, digital image processing, and related mathematics I encourage you to write custom software like the aforesaid; it will be an entertaining and enriching experience.
Regards.