Is there a way to add a label item that is connected to a handle of a lineROI

[Luka Drmic]

As the title suggests. Is there a way to add a LabelItem() that is connected  to a Handle() of a lineRoi(). Meaning it follows the handle if the handle is moved.

Thanks.

[Patrick]

Hi,

This isn't very flexible (you'll need to update the list of handles if any are added/removed) but should be a start:

#!/usr/bin/env python3

from PyQt5 import QtWidgets
import pyqtgraph as pg

class TestPlot(pg.GraphicsLayoutWidget):

    def __init__(self):
        super().__init__()

        self.plot = self.addPlot()
        self.roi = pg.LineSegmentROI(positions=[(0.25, 0.25), (0.75, 0.75)])
        self.plot.addItem(self.roi, ignoreBounds=True)
        self.plot.disableAutoRange()
        self.roi.sigRegionChanged.connect(self._roi_changed)

        self.roi_labels = [ pg.TextItem(text='label', anchor=(0.5, 1.0)) for _ in self.roi.getHandles() ]
        for label in self.roi_labels:
            self.plot.addItem(label)
        self._roi_changed()

    def _roi_changed(self):
        for h_i, handle in enumerate(self.roi.getHandles()):
            handle_pos = self.roi.pos() + handle.pos()
            self.roi_labels[h_i].setPos(handle_pos)
            self.roi_labels[h_i].setText("{}, {}".format(round(handle_pos[0], 2), round(handle_pos[1], 2)))

def main():
    import sys
    app = QtWidgets.QApplication(sys.argv)
    mainwindow = TestPlot()
    mainwindow.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Patrick

[Luka Drmic]

I went with something similair.

self.label_a = pg.TextItem("[A]", color=(255, 255, 255))
self.label_a.setAnchor((0, 1))
self.label_a.setParentItem(line_segmet_roi)
self.label_a.setPos(x0, y0)
self.label_b = pg.TextItem("[B]", color=(255, 255, 255))
self.label_b.setAnchor((0, 0))
self.label_a.setParentItem(line_segmet_roi)
self.label_b.setPos(x1, y1)

def update_point_label_positions(self):
    point1 = self.line_segment_roi["ROI"].getSceneHandlePositions(0)
    _, scene_coords = point1
    coords_a = self.line_segment_roi["ROI"].mapSceneToParent(scene_coords)
    point2 = self.line_segment_roi["ROI"].getSceneHandlePositions(1)
    _, scene_coords = point2
    coords_b = self.line_segment_roi["ROI"].mapSceneToParent(scene_coords)

    self.label_a.setPos(coords_a.x(), coords_a.y())
    self.label_b.setPos(coords_b.x(), coords_b.y())

Thx for your reply. Luka.