[Qt-interest] Get raw data from QImage

[Cole, Derek]

Sorry - accidentallly sent last mail.

As I was saying, I want to get the raw data back out of a section of the QGraphicsItem, so I used code like this:

    QPixmap fullPmap = topItem->pixmap();
    fullPmap = fullPmap.copy(isec.toRect());
    QImage chip = fullPmap.toImage();


so I know that chip has the right section in it, because I can use "display code" like I just posted with chip as the image instead of qi, and it works.

However, I need to get the raw data back from chip, so that I can send it off to another 3rd party library that is expecting a single unsigned char *

In my case, as you can see from the way I created the image in the display code below, I just want to send it a single band, since it has been displayed as grayscale anyway.

I tried to use chip.bits() but that is giving me some data that is unusable, apparently, or I am using it wrong.

So what is the proper way to do this?


________________________________
From: Cole, Derek
Sent: Wednesday, April 27, 2011 7:33 PM
To: qt-interest at qt.nokia.com
Subject: Get raw data from QImage

Hello,

I have populated a QGraphicsPixmapItem with an image using code similar to the following:

    QImage *qi = new QImage(imwidth, imheight, QImage::Format_RGB32);
        for (int i = 0 ; i < imheight ; i++)
        {
             for (int j = 0 ; j < imwidth ; j++)
             {
                    qi->setPixel(j,i,qRgb(imageData[i*imwidth+j],imageData[i*imwidth+j],imageData[i*imwidth+j]));

             }
         }

    QPixmap p(QPixmap::fromImage(*qi,Qt::AutoColor));
    if(scene.items().contains(item)){
        scene.removeItem(item);
        item->~QGraphicsItem();
    }
    item = new ImagePixmapItem(p);
    scene.addItem(item);

Now I want to get the data back from one of those QGraphicsItems and I am using some code like this to get the QImage of a particular part of the image:



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