PyQt QImage cna't copy, crash without error code

[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)

[darrenleeleelee1]

@KroMignon I change but still crash...What is the different between arr and arr.data?

[KroMignon]

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

What is the different between arr and arr.data?

arr is an instance of numpy.ndarray type, according to your code!
And arr.data is the data buffer according to numpy documentation ==> https://numpy.org/doc/stable/reference/generated/numpy.ndarray.html

I think it would be great if you first explain what you want to do.
Perhaps you should take a look at this python script which converts numpy.ndatarray to QImage and vice versa:
https://kogs-www.informatik.uni-hamburg.de/~meine/software/vigraqt/qimage2ndarray.py

[darrenleeleelee1]

@KroMignon I saw this before, but I don't know how to apply to uint16.

[KroMignon]

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

I saw this before, but I don't know how to apply to uint16.

Which version of Qt-Libs are you using?
Format_Grayscale16 is only support starting from Qt 5.13 (cf. QImage.Format)

Because of this note from documentation:

Constructs an image with the given width , height and format , that uses an existing memory buffer, data . 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.

Perhaps you should specify the number of bytes per line, like this:

qimage = QtGui.QImage(arr.data, arr.shape[1], arr.shape[0], arr.shape[1]*2, QtGui.QImage.Format_Grayscale16)

[darrenleeleelee1]

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

arr.shape[1]*2

sorry, I read through the QImage API, but I don;t get why I need to add this.
After I add this it seems can work.

[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

[darrenleeleelee1]

@KroMignon @J-Hilk @JonB @jsulm thanks all u guys!