How To Spend QImage To Opencv?

qazaq408

Now I need to Operat picture in program.
win7 + Qt5.7+ vs2013 +opencv3.1

   I choose opencv to operat picture,the picture is coming another progran and his format is QImage, I need give the QImage to openCV's funtion ,but openCV's funtion can't read this format(QImage);
 I have to save QImage to local file ,then opencv's funtion read the local file ,like this

QString pixPath = tr("F:/pix/1.png");
testPix.save(pixPath); //testPix is a QImage
IplImage* sImg = cvLoadImage(pixPath.toStdString().c_str(),1); //use opencv funtion

but the is a problem,i need save QImage to local disk and read out again,this will impact the speed of the program,can I spend QImage to opencv's funtion dirctly?

jsulm

@qazaq408 For sure not directly. I don't know the OpenCV API. First you need to check OpenCV documentation and see what you can pass to it. Is there something like loadFromData(char*) (this is just an example)?

J.Hilk

@qazaq408
I stumbled across this git-project a while a go. It should solve your issue.

SGaist

Hi,

Before anything else, why do you need to pass a QImage to OpenCV ? Can't you use OpenCV directly ? What's the source of the image ?

Pablo J. Rogina

@qazaq408 if you really need to pass a Qt image to OpenCV you may want to do something like this:

QImage preview;
...
auto image = cv::Mat(preview.height(),
    preview.width(),
    CV_8UC4,
    const_cast<uchar*>(preview.bits()),
    preview.bytesPerLine());

The project mentioned in @J-Hilk post could also help you understand the process. Pay attention to the QImage's format (i.e. QImage::Format_RGB32, QImage::Format_ARGB32, etc.)

And also as @SGaist told you, think if it's completely necessary to do such image conversion (Qt <-> OpenCV). You may end up doiing all the image related work in OpenCV alone (i.e. reading, manipulating and saving an image file) within a Qt application.