This helps in previewing how each spritesheet frame will look when it will be imported in Pixelorama. Note that this does not work well with non-square images at the moment.
More specifically, moved scale, crop, invert, desaturate and generate outline code to DrawingAlgos.gd. I am a little worried of DrawingAlgos.gd getting too big though.
Instead of setting the main arrow as a custom cursor every time the cursor gets inside the viewport, set the viewport's default cursor to be the cross, and change the cross's image once in Global.gd
https://github.com/godotengine/godot/issues/31124 has now been fixed in Godot 3.2.2-rc1, so we can use Image.blend_rect() instead of a custom method. This makes exporting large images and drawing with large brush sizes a lot faster.
Once Godot 3.2.2 stable is released, the custom blend_rect method will be completely removed.
The "Open" option will handle importing of .pxo files and image files from now on. The "ImportSprites" file dialog node and script are scheduled to be deleted too. Importing spritesheets option will return soon. Next thing I'm going to work on is a preview window that will appear when importing image files.
The structure of the .pxo files is now consisted of a JSON-structured metadata part, where all the data that can be stored as text are, and a binary part, that contain all the actual image data for each cel and project brush.
This makes it easier for users to understand the .pxo structure, easier to add more changes without having to check versions for backwards compatibility, easier to be opened by third-party apps and it allows us to make an "Export JSON metadata" option, that will export just the metadata in JSON format, without the binary image data.
It's backwards compatible and .pxo files from as far as v0.5 are still supported.
If the current project is empty (only 1 layer and frame, no tags and the image has no content - is invisible) and the user is opening a project, then the opened project will not open a new tab of its own, and will use the currently opened one instead.
Importing a non-palette json file no longer crashes the app. Enabled autowrap for a label in EditPalettePopup because some translated text were pushing the boundaries of the dialog window.
