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 ?