Export to SVG with opacity on items

[ElpadoCan]

It would be very nice if the opacities of the items were respected when exporting to SVG.

Opacities are set with setOpacity method of the ImageItem (which very conveniently works with any other item).

Here is a minimal example where the resulting image is grey (black blended with white). However, the saved SVG is two images, one black and one white and the opacity of the white image is 100% (instead of 50% that was set in the code).

import numpy as np

import pyqtgraph as pg
from pyqtgraph.Qt import QtCore

app = pg.mkQApp("Blend images example")

## Create window with GraphicsView widget
w = pg.GraphicsView()
w.show()
w.resize(800,800)
w.setWindowTitle('Two images blended with opacity')

view = pg.ViewBox()
w.setCentralItem(view)

## lock the aspect ratio
view.setAspectLocked(True)

## Create image item
img1 = pg.ImageItem(np.zeros((200,200)))
img1.setLevels([0, 1])
view.addItem(img1)

## Create image item
img2 = pg.ImageItem(np.ones((200,200)))
img2.setLevels([0, 1])
view.addItem(img2)
img2.setOpacity(0.5)

## Set initial view bounds
view.setRange(QtCore.QRectF(0, 0, 200, 200))

if __name__ == '__main__':
    pg.exec()

Displayed image in the app:

Saved SVG: