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import numpy as np
import pyqtgraph as pg
def test_qimage_writethrough():
w, h = 256, 256
backstore = np.ones((h, w), dtype=np.uint8)
ptr0 = backstore.ctypes.data
fmt = pg.Qt.QtGui.QImage.Format.Format_Grayscale8
qimg = pg.functions.ndarray_to_qimage(backstore, fmt)
def get_pointer(obj):
if hasattr(obj, 'setsize'):
return int(obj)
else:
return np.frombuffer(obj, dtype=np.uint8).ctypes.data
# test that QImage is using the provided buffer (i.e. zero-copy)
ptr1 = get_pointer(qimg.constBits())
assert ptr0 == ptr1
# test that QImage is not const (i.e. no COW)
# if QImage is const, then bits() returns a copy
ptr2 = get_pointer(qimg.bits())
assert ptr1 == ptr2
# test that data gets written through to provided buffer
qimg.fill(0)
assert np.all(backstore == 0)
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