In Winter of 2024 I was looking for a project to do and had a simple problem I wanted to solve. (A problem that is probably solved in photoshop like apps) I ended up deciding to start on a basic version of my own MS Paint. The feature I wanted though, was the ability to use the paint bucket, but instead of a flood fill, it would convert any pixel of the current color to the new color within the whole image. I primarily wanted this to take things like qr codes and quickly change the colors without breaking them. I could also have my paint bucket have transparent or empty as the color and paint bucket fill could do it for me!
So I put together a program that loads an image from disk, and displays it on the screen and allows you to edit it with a brush tool as well as paint bucket. I added the few random features I wanted, and then messed around with things like visual fill so I could watch the paint bucket flood fill things like mazes. After I got these basics running, I had this brilliant idea to make it so that whenever I opened any png on my computer it would go to my build instead... when you have never changed a default program to something you are currently developing, windows has this problem of caching programs in the list even if you delete them entirely. At one point my open with window had like 10 versions of cocoimage in it and none of them worked! Eventually I got it all figured out and have this fun gui app that I can use for basic MS paint operations, and similar pixel color swaps. I set it to be the default for bitmaps, so I still use it fairly often as my screenshot hotkey defaults to bitmap.
Even though I put it together fairly quickly, it has been super reliable. I just checked and the "installed" version of it on my computer was a release build that has a date of 12/19/2024 and I use it multiple times a week and it has never once failed me or crashed!