GPencil: New operator to convert strokes to perimeter.

This operator converts any stroke of gpencil with a center line into a stroke with the perimeter.

It's possible to assign the active material, keep current or create a new material for all perimeters.

The conversion is only done for strokes with a material using `Stroke`. Only `Fill` strokes are not converted.

Known issues: As the perimter has not boolean implementation, some perimeters can be overlaped. This could be solved in the future when a new 2D boolean library will be developed.

Reviewed By: mendio, pepeland, frogstomp

Differential Revision: https://developer.blender.org/D15664

release/scripts/startup/bl_ui/space_view3d.py

@@ -5178,6 +5178,9 @@ class VIEW3D_MT_edit_gpencil_stroke(Menu):
         layout.separator()
         layout.operator("gpencil.reset_transform_fill", text="Reset Fill Transform")
 
+        layout.separator()
+        layout.operator("gpencil.stroke_outline", text="Outline")
+
 
 class VIEW3D_MT_edit_gpencil_point(Menu):
     bl_label = "Point"