I am having trouble with the coordinates used to create a RectROI centered
on the position of a mouse click.
For example if I have an image displayed:
import pyqtgraph as pg
import numpy as np
pw = pg.PlotWidget()
img = pg.ImageItem(np.random.normal(size=(400,400)))
pw.addItem(img)
then I can get us position of a user click by hooking into
img.sigMouseClicked
img.sigMouseClicked.connect(drawRect)
def drawRect(pos):
# img coordinates
imc = img.mapFromScene(pos)
width = 10
height = 10
rect = pg.RectROI(pos=, size=(width, height))
pw.addItem(rect)
I am unsure of how to format the position of the rectangle such that the
center is the coordinates of the mouse click (in image coordinates). The
documentation suggests that the pos argument should be the coordinates of
the lower left corner of the rectangle. However, do these coordinates need
to be given in the scene coordinate system rather than the image coordinate
system?
Would the correct transformation be as follows?
pg.RectROI(pos=img.mapToScene(imc.x() - width/2, imc.y() + height/2),
size=(width, height))
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