Bitmap Coloring layer version 2, with preview for scanned drawings

[davidlamhauge]

I have made some changes based on the response I've got so far, so here is version 2 of the bitmap coloring feature.
A new video can be seen here.
I look forward to hear comments and suggestions for improvements.

[davidlamhauge]

I have updated this feature so it is more logical and user friendly.

1. I have removed the process of making scanned drawings transparent, from the coloring window. The 'Pegbar alignment' entry in 'Edit' is now called 'Prepare scanned drawings', with two menu entries: 'Pegbar alignment' and 'Add transparency to paper'.
   In the 'Add transparency to paper', you get a preview window, so you can see how the drawing will look when transparency is added.
2. The coloring process is more informative, and should hopefully give the user a good experience.

I have removed the WIP. This is ready for review.

[davidlamhauge]

Her is a 10 minute video, where I show how three scanned drawings end up like three beautiful colored animation frames. New changes are shown.
https://youtu.be/6C4AUjyueYE

[Jose-Moreno]

Her is a 10 minute video, where I show how three scanned drawings end up like three beautiful colored animation frames. New changes are shown.
https://youtu.be/6C4AUjyueYE

Nice job! 🎉 This is certainly a great step forwards as many exciting opportunities will open just by adding the current feature.

Once this is reviewed and merged I'm hoping other contributors will be interested in bringing back and expanding the color layer "bleed" feature for the fill tool. I'm sure such tool will synergize well with this coloring feature, allowing the user to color selected target layers automatically by using a a specific layer as an alpha mask reference, such as a lineart layer would be very interesting 👍

Similarly if and when we manage to also get back the fill expand feature the old Pencil used to have, people will be able to color depending on their preferred workflow: either with separate layers like the current implementation or on the same layer without halo artifacts as seen in opentoonz or retas paintman.

Another path of future improvement that will hopefully come once this PR is merged is the automatization of the blending feature, particularly when using the fill tool on color traced drawings to fill highlight and shadow areas directly (i.e color traces).

Either way thank you for opening so many potential doors for enhancement! Once again great job 🙌 😄

[davidlamhauge]

Thanks @Jose-Moreno. Yes, the feature has been improved, and is maybe more logical now, where you prepare your drawings first, and then use the coloring feature.

Your old wish for the color bleed and expand feature is not forgotten. The last week I've had many debug sessions with CandyFace, and one thing we talked about (while waiting for compilation) was this feature. If you look at the drawings used in my video, these drawings could easily have been colored with the bleed/expand coloring. My coloring is mainly necessary if you have shadows, highligths and the like.