This patch is adding some code in order to extract a drawing as curves from an image.
The algorithm is basically the following:
- reduce the dimensions
- make it gray
- apply a bilateral filter in order to add some blurryness while keeping the edges
- compute the histogram
- guess what's the background color which should contain a large majority of the pixels
- make a binary image
- extract the contours in using the Suzuki algorithm
- apply the Douglas-Peucker algorithm in order to reduce the number of points
The algorithm is improvable but it should work pretty well if there's a clear difference between
the background and the drawing.
In a v2 we could use a ML model in order to improve the extraction.
There's few changes related to the UI in order to make the tool usable, but they're very basic
for the moment.
This patch fixes a bug that caused incorrect curve shapes when an endpoint lies beyond the page boundaries. It adds a check for the endpoint's position, and if it is outside the page, the point is excluded from the shape's coordinates.
- it's now possible to start a drawing with a pen and use fingers to zoom
or scroll without interacting with the current drawing;
- it's now possible to draw with a finger and them zoom with two fingers.
When a user deletes any number of annotations, they are notified of the action
by a popup message with an undo button. Besides that, this change reuses the
existing messageBar CSS class from the new alt-text dialog as much as possible.
This patch makes a clear separation between the way to draw and the editing stuff.
It adds a class DrawEditor which should be extended in order to create new drawing tools.
As an example, the ink tool has been rewritten in order to use it.
