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)