Get the size of jpg file of QImage file before saving it.

samdol

Hi,

I could get the target QImage from source QImage by the following snippet.

    QByteArray ba;
    QBuffer buffer(&ba);
    buffer.open(QIODevice::WriteOnly);
    QImageWriter writer;
    writer.setDevice(&buffer);
    writer.setFormat("jpg");
    writer.setQuality(88);
    writer.write(image_source);
    image_target.loadFromData(ba);

Is there any way which tells me how much kilo byte this jpg file would take up even before I save it to disk?
I tried to use buffer.data.size(), but it seems give me the size before jpg compression.

SGaist

Hi,

No, because it depends on what your image contains.

By the way, why are you using such a complicated way to copy data from image_source to image_target ?