Resource path for non-qt functions
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@Engelard
I have explained, I don't know how to explain it any clearer.If you ship a resource, it isn't an external file, you can't pass it to OpenCV anything.
A resource is addressed via
:/...path. That is not a real file. The only thing that can open it isQFile.Use that to open its content for read. Read its whole content, writing that to a real, external file. [EDIT @SimonSchroeder shows later on that you can simply use
QFile::copy()to do this in one line.] Pass the path of that extracted file to your external OpenCV.If you don't understand this, you can't use a resource file for your purpose of passing it to OpenCV. In that case give up on resources and supply the file as an external file, not a resource.
wrote on 11 Aug 2020, 23:03 last edited by@JonB said in Resource path for non-qt functions:
Read its whole content, writing that to a real, external file.
you mean - make a copy of that file from resources? Even if i'll do that, i should create folder for that .jpg file, so it would'nt be messy, and then i should delete that copy when my program is about to be closed. Am i right?
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wrote on 11 Aug 2020, 23:54 last edited by
Problem "resolved". From this topic i understand that i can't acces .res files of my qt app, it's okay. But then i found that i'm not able to simply use relative path's in my app for some strange qt reason.
So i found such wonderful static function - QString QCoreApplication::applicationDirPath(); which returns directory of running app, then simply add desired "relative" path QString and here we go!
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wrote on 11 Aug 2020, 23:55 last edited by Bonnie 8 Dec 2020, 00:06
What OpenCV functions are you planning to use with the image files?
If you only use cv::imread you can try to replace that with QFile + cv::imdecode or create a cv::Mat directly from a QImage. -
What OpenCV functions are you planning to use with the image files?
If you only use cv::imread you can try to replace that with QFile + cv::imdecode or create a cv::Mat directly from a QImage.wrote on 12 Aug 2020, 00:08 last edited by Engelard 8 Dec 2020, 00:20@Bonnie said in Resource path for non-qt functions:
or create a cv::Mat directly from a QImage.
Tnx. I just started with OpenCV, by now need exactly Mat creation. Which one is better for performance? From QFile or from QImage?
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wrote on 12 Aug 2020, 00:35 last edited by
Bonnie, you just saved the day. Because of your hint i found this golden
answerwork of art: https://stackoverflow.com/a/33923407 Everything tested and well explained, conversion from QFile as he mentioned 10 times faster then from QImage. -
Problem "resolved". From this topic i understand that i can't acces .res files of my qt app, it's okay. But then i found that i'm not able to simply use relative path's in my app for some strange qt reason.
So i found such wonderful static function - QString QCoreApplication::applicationDirPath(); which returns directory of running app, then simply add desired "relative" path QString and here we go!
wrote on 12 Aug 2020, 07:35 last edited by@Engelard said in Resource path for non-qt functions:
So i found such wonderful static function -
QString QCoreApplication::applicationDirPath();which returns directory of running app, then simply add desired "relative" path QString and here we go!Which is why I wrote to you earlier on:
When you open files at runtime you would be best making a full path to them. If you plan to pass this path to an external program, you may be advised to pass the full path. There are Qt methods to provide strings for the path, e.g. https://doc.qt.io/qt-5/qcoreapplication.html#applicationDirPath.
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@Engelard said in Resource path for non-qt functions:
So i found such wonderful static function -
QString QCoreApplication::applicationDirPath();which returns directory of running app, then simply add desired "relative" path QString and here we go!Which is why I wrote to you earlier on:
When you open files at runtime you would be best making a full path to them. If you plan to pass this path to an external program, you may be advised to pass the full path. There are Qt methods to provide strings for the path, e.g. https://doc.qt.io/qt-5/qcoreapplication.html#applicationDirPath.
wrote on 12 Aug 2020, 12:53 last edited by@JonB said in Resource path for non-qt functions:
Which is why I wrote to you earlier on:
Yeah, back then i did'nt give it serious attention, was thinking that using relative path's it is the only right way for program to use it's own files.
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@JonB said in Resource path for non-qt functions:
Which is why I wrote to you earlier on:
Yeah, back then i did'nt give it serious attention, was thinking that using relative path's it is the only right way for program to use it's own files.
wrote on 12 Aug 2020, 12:54 last edited by JonB 8 Dec 2020, 12:57@Engelard said in Resource path for non-qt functions:
Yeah, back then i did'nt give it serious attention
Yeah, that's nice to hear ;-) I'll bear it mind for my future replies to you :D :D [<-- For the avoidance of any misinterpretations: winks/smileys!]
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wrote on 13 Aug 2020, 07:09 last edited by
@Engelard One thing to consider – as you have mentioned that OpenCV might also be writing (to) files – is that if you distribute your app and people install it properly they might not be able to write into the applications folder. Usually, these folders are only writeable for administrators/root. Have a look at https://doc.qt.io/qt-5/qstandardpaths.html to figure out where to put which kind of files. Furthermore, there is
QTemporaryDirandQTemporaryFileif the data is supposed to only exist until you close your software.BTW: If you provide something inside your resources and need to have a copy inside the real filesystem, a simple
QFile::copy(":files/lego.jpg", "/some/tmp/path/files/lego.jpg")is sufficient. You don't need to open the file and read it in. (Though your solution you found on StackOverflow is also valid.)
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