How to save a QPixmap Object to a file?

Question

I'm having trouble reading and writing QByteArray data to a file.

My goal is to save QPixmap data into a QByteArray and save that QByteArray to a file (with the ability to read this QByteArray back from the file and into a QPixmap). I want to use following code from the QPixmap documentation:

     QPixmap pixmap(<image path>);  
     QByteArray bytes;
     QBuffer buffer(&bytes);
     buffer.open(QIODevice::WriteOnly);
     pixmap.save(&buffer, "PNG"); // writes pixmap into bytes in PNG format

After writing the buffer to a file, I want to be able to retrieve the QByteArray and load it back into a QPixmap using the QPixmap::loadFromData() function.

Please let me know if any further clarification is needed (I'm open to alternative approaches as well, I just need to be able to read and write the QPixmap to a file! :) );

Frisket

Answer 1

That seemed like a really long way to go about doing it (but your comment better explains):

For writing:

QFile file("yourFile.png");
file.open(QIODevice::WriteOnly);
pixmap.save(&file, "PNG");

For reading:

QPixmap pixmap;
pixmap.load("yourFile.png");

QBuffer is great when you need a QIODevice and want to keep it in memory, but if you're actually going out to disk, then it's an unnecessary middle step.

EDIT:

To write pixmaps, and other things, to a single file I'd recommend that you use QDataStream.

For writing:

QFile file("outfile.dat");
file.open(QIODevice::WriteOnly);
QDataStream out(&file);
out << QString("almost any qt value object")
    << yourQPixMap << yourQList /* << etc. */;

Then, you can do similarly for reading:

QFile file("infile.dat");
file.open(QIODevice::ReadOnly);
QDataStream in(&file);
in >> firstQString >> yourQPixmap >> yourList /* >> etc. */;

You'll need to make sure that you read in the same objects as you wrote them out. In order to save yourself future compatibility headaches, set the QDataStream version explicitly.

Saidel

This solution is great but I need to be able to save multiple image data along with text to a single file. For example, my file would contain picture 1 title, picture 1 info... etc <Associated QPixmap data> picture 2 title, picture 2 info... etc <Associated QPixmap data> Any suggestions? – Frisket