Thanks to https://godotshaders.com/shader/color-manipulator/
The shader has more options than just brightness and contrast though, but I didn't know how else to name the effect. "Adjust Brightness/Contrast" makes it immediately obvious as to what the effect is about.
This will allow us to implement shearing more easily. Also, for the non-SmearRotxel shaders, normalize their pivot in GDScript, before passing it to the script. Should probably be faster this way
Pixelize makes the image pixelated, and Palettize maps the color of the input to the nearest color in the selected palette. Useful for limiting color in pixel art and for artistic effects.
* Basic logic for layer effects
* Add an FX button and the ability to add effects, no way to remove or change properties of effects yet
* Basic and ugly UI for adding and removing effects, no property changing yet
* Swap effects
* Fix preload shader paths
* Change parameters for layer effects
* Change gradient parameter in layer effect shaders, and other fixes
* Use CollapsibleContainers for the shader properties
* Set the correct gradient interpolation mode and color space in the UI
* Make effects of group layers apply to children
* Change `apply_fx` to `apply_effects`, formatting, some extra doc comments
* Apply effects to other canvases, when merging layers and when exporting
* Display humanized names of the shader unifrms
* Some UI improvements to the LayerEffectsSettings
* Add an Enabled button in the layer effects window, and change checkboxes to checkbuttons
* Change BaseLayer.apply_effects() to take a cel as a parameter instead
* Make layer effect buttons be affected by the modulate icon color
* Add option in the View menu whether layer effects are displayed in the canvas or not
* Rename `apply_effects()` to `display_effects()`
* Add translation strings
* Add nearest filter to the gradient map
* Don't change Main.tscn
* Fix more translations
* Change the default cursor shape of the generated UI elements of the layer effects
* Add undo/redo and effect application (apply effect destructively)
There are some errors due to the usage of anonymous lambda methods in undo/redo, but it seems to be working well regardless.
* Make layer effect application work on all cels
