Plots disappeared when update image

[Ellito]

I have multiple items displayed on the pyqtgraph plotWidget, an image and some lines. When I update the image, the line are also removed and not displayed. Could someone advise a way to update the image without removing the lines (I do not want to redraw the line again since it will delay the real-time display)?

Example:

import numpy as np 

import pyqtgraph as pq 

img = np.random.rand(100,100) 

itemShow = pg.ImageItem(img.T) 

imgItem = imWidget.addItem(itemShow) 

penL = pg.mkPen('r') 

lineItem = imWidget.addLine(x=100, pen=penL)

After I updating the imgItem , the line is disappeared at the window.

[Patrick]

Hi,

I'm assuming that you need to ensure the "z-order" of the items is correct (the lines need to be in front of the image). Either insert the image first, then the line plot (and then only update the plot with setData). Or specifically change the z-order with the

setZValue(...) method of the GraphicsItems. This functionality is inherited from the Qt QGraphicsItem https://doc.qt.io/qt-5/qgraphicsitem.html#setZValue which is why it's hard to find...

Patrick