PyQt QImage cna't copy, crash without error code

[darrenleeleelee1]

I want to show on a QImage and translate to QPixmap, but when I want to manipulate(copy, scaled, or construct by QPixmap) qimage then the process will crash.But If I copy to a small rectangle like(2048, 2048) It was not crash any more.

This arr is numpy ndarray, shape:(3408, 2235) dtype:uint16, maximum value is 65535 and minimum is 0.

I wonder why the process will crash without error code.

How can I fix it?

from PyQt5 import QtCore, QtGui, QtWidgets
from pydicom import dcmread
import numpy as np
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(2048, 2048)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.photo = QtWidgets.QLabel(self.centralwidget)
        self.photo.setGeometry(QtCore.QRect(0, 0, 2048, 2048))
        self.photo.setText("")
        ds = dcmread('./5F329172_20170623_CR_2_1_1')
        arr = ds.pixel_array
        print("ndarray shape: ", arr.shape, " dtype: ", arr.dtype)
        print("ndarray max: ", np.max(arr), " min: ", np.min(arr))
        qimage = QtGui.QImage(arr, arr.shape[1], arr.shape[0], QtGui.QImage.Format_Grayscale16)
        qimage = qimage.copy()
        # qimage = qimage.copy(QtCore.QRect(0, 0, 2048, 2048)) this will not crash
        pixmap = QtGui.QPixmap.fromImage(qimage)
        self.photo.setPixmap(pixmap)
        self.photo.setScaledContents(True)
        self.photo.setObjectName("photo")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)


    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
     

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

dicom data: 5F329172_20170623_CR_2_1_1

[KroMignon]

@darrenleeleelee1 said in PyQt QImage cna't copy, crash without error code:

sorry, I read through the QImage API, but I don;t get why I need to add this.

Then you don't read carefully ;)
The point is when you only specify width and height: The width and height must be specified in pixels, data must be 32-bit aligned, and each scanline of data in the image must also be 32-bit aligned.

To avoid this, you can use width, height and scanline length in bytes, which is pixel_per_line x pixel_size:

• pixel_per_line is arr.shape[1]
• pixel_size is uint16 which are 2 bytes

==> scanline_size = arr.shape[1]*2

After I add this it seems can work.

Great

[jsulm]

@darrenleeleelee1 said in PyQt QImage cna't copy, crash without error code:

I wonder why the process will crash without error code.

Did you use debugger to see where exactly it is crashing?
You should also check https://doc.qt.io/qt-5/qpixmap.html#isNull and https://doc.qt.io/qt-5/qimage.html#isNull before using the QImage/QPixmap.

[darrenleeleelee1]

@jsulm I used debugger, it will process to qimage = qimage.copy() this command,then just crash without any error code.And I try to use qimage.isNull() it return False.

[J.Hilk]

@darrenleeleelee1 out of curiosity, does it also crash, if you try to not copy it into itself but a different variable?

[darrenleeleelee1]

@J-Hilk said in PyQt QImage cna't copy, crash without error code:

curiosity

Yes,it also crash.

[JonB]

@darrenleeleelee1 said in PyQt QImage cna't copy, crash without error code:

    qimage = qimage.copy()
    # qimage = qimage.copy(QtCore.QRect(0, 0, 2048, 2048)) this will not crash

So do you want to tell us what qImage.width() & qImage.height() of the image actually are?

[jsulm]

@darrenleeleelee1 Did you check whether the image is a null image as I already suggested?

[JonB]

@jsulm
He claims

And I try to use qimage.isNull() it return False.

assuming this check is done in the right place.

[jsulm]

@JonB I need to read more carefully sometimes :-)

[darrenleeleelee1]

@JonB
and it return 2235 3408
@J-Hilk I copy to tmp and it still crash.

[JonB]

@darrenleeleelee1
Then OOI how does

qimage = qimage.copy(QtCore.QRect(0, 0, 2235, 3408))

behave?

[darrenleeleelee1]

@JonB It won't crash!But when I change to

qimage.copy(0, 0, qimage.width(), qimage.height()) 

then it crash.Even I give to other variable first it still not work

wt = qimage.width()
ht = qimage.height()
qimage = qimage.copy(0, 0, wt, ht)

[J.Hilk]

@darrenleeleelee1 what about
qimage = qimage.copy(QtCore.QRect())

[darrenleeleelee1]

@J-Hilk I try it.But also crash.

[KroMignon]

@darrenleeleelee1 said in PyQt QImage cna't copy, crash without error code:

qimage.copy(0, 0, qimage.width(), qimage.height())

then it crash

It looks very strange to me, because when looking for QImage::copy(int x, int y, int w, int h), I found:

   inline QImage copy(int x, int y, int w, int h) const
        { return copy(QRect(x, y, w, h)); }

What if when you change your code to:

qimage = QtGui.QImage(arr, arr.shape[1], arr.shape[0], QtGui.QImage.Format_Grayscale16)
qimageCopy = qimage.copy()

Does this also crash?

[JonB]

@darrenleeleelee1 said in PyQt QImage cna't copy, crash without error code:

@JonB It won't crash!But when I change to
qimage.copy(0, 0, qimage.width(), qimage.height())

then it crash.Even I give to other variable first it still not work
wt = qimage.width()
ht = qimage.height()
qimage = qimage.copy(0, 0, wt, ht)

This all implies that the source qimage you start with is the issue.

Start by looking at exactly what your arr = ds.pixel_array holds/returns. The QImage() constructor you use states "it must remain valid". That looks to me like the danger area. I think when you copy a portion of the image Qt takes a copy of its own. But probably not when you copy the whole thing. For example, are you able to do a Python copy() on it so you have your own separate copy, which you then use for the image? And btw, if you have any threading involved anywhere, please say so......

[darrenleeleelee1]

@JonB Sorry I am not really get what did you mean.And I think I don't have any threading.(I think..)

[JonB]

@darrenleeleelee1
I have no idea what is behind your

        ds = dcmread('./5F329172_20170623_CR_2_1_1')
        arr = ds.pixel_array

It's some external library stuff. (And btw I have no idea whether arr.shape[1], arr.shape[0] is the right thing to use. Don't bother to explain, just make sure it's correct for whatever this ds stuff is.)

Try this:

import copy
...
        arr = copy.copy(ds.pixel_array)
# or even:
#        arr = copy.deepcopy(ds.pixel_array)

before you proceed to qimage = QtGui.QImage(arr, ...). Any better, crash-wise?

[darrenleeleelee1]

@JonB
I add deepcopy,and it also crash. I add some arr attribute for you.

[KroMignon]

@darrenleeleelee1 I think you should change your code to:

qimage = QtGui.QImage(arr.data, arr.shape[1], arr.shape[0], QtGui.QImage.Format_Grayscale16)