Adding ability to add or remove points from existing polygon when lef…

…t-clicking while holding down the SHIFT-key.

labelme/widgets/canvas.py

@@ -376,6 +376,19 @@ def mouseReleaseEvent(self, ev):
  self.repaint()
  elif ev.button() == QtCore.Qt.LeftButton and self.selectedShapes:
  self.overrideCursor(CURSOR_GRAB)
+ if (
+ self.editing()
+ and int(ev.modifiers()) == QtCore.Qt.ShiftModifier
+ ):
+ # Add point to line if: left-click + SHIFT on a line segment
+ self.addPointToEdge()
+ elif ev.button() == QtCore.Qt.LeftButton and self.selectedVertex():
+ if (
+ self.editing()
+ and int(ev.modifiers()) == QtCore.Qt.ShiftModifier
+ ):
+ # Delete point if: left-click + SHIFT on a point
+ self.removeSelectedPoint()
 
  if self.movingShape and self.hShape:
  index = self.shapes.index(self.hShape)