Writing a QRGB.name() to a file, then reading it back out

Pollarm

Hello,

I am attempting to take a QImage, and pass the values of all of its pixels to a file, so that I can read it out again later to reconstruct the same image. I'm feeding the QRGB names to a file with:

    QDataStream out(&qFile);
    qFile.open(QIODevice::WriteOnly);
    for (int i = 0; i < img.height(); ++i) {
        for (int j = 0; j < img.width(); ++j) {
            if(img.valid(i, j)){
                QString str = img.pixelColor(i,j).name();
                out << str;
            }
        }

    }
    qFile.close();

But I have been unable to retrieve the QRGB.name() values from the file in a way that I can pass them into a QRGB and construct the color. QImage::setPixelColor always comes back with an invalid color reponse. Any tips, help, or suggestions on this would be greatly appreciated, thanks!

mrjj

Hi
Are you using
https://doc.qt.io/qt-5/qcolor.html#setNamedColor
when you read it in again ?

Also you could save directly the QColor

out << img.pixelColor(i,j);

JonB

@Pollarm said in Writing a QRGB.name() to a file, then reading it back out:

I am attempting to take a QImage, and pass the values of all of its pixels to a file, so that I can read it out again later to reconstruct the same image. I'm feeding the QRGB names to a file

Are you doing this because you wish to, for some reason/exercise? Saving the values of every pixel in an image, one at a time, as a string name, is not a usual format for saving in... :)

SGaist

Hi,

QImage::save is likely going to be a simpler solution.

Pollarm

@JonB The project I'm working keeps multiple images at the same time (drawing one on top of the other), and for the functionality of saving/loading a project in progress I was attempting the angle of encoding the pixels into a file to be read back from later to reconstruct the base image and the one in progress. We decided on encoding for size of the save file reasons. Is there a better way to do this that I didn't think of? Thanks :)

mrjj

@Pollarm
Hi
https://doc.qt.io/qt-5/qdatastream.html
can be used to directly save QImage to a file.
So you can construct a "project image" by
simply streaming the different images to the same file
and the opposite direction will also be easy.
Depending on how you have the images stored ( like QVector)
you can also stream the whole list back and forths directly.

Pollarm

@mrjj Thanks! That was so much simpler, and worked like a dream. I think I tried using QDataStream right at the outset of this undertaking, but apparently I was using it incorrectly because I could never get it to construct the image properly!