QPixmap QImage

QPixmap   QImage

void ScrollBox::setThumbnail(QPixmap img)
{
    QPixmap bkPixmap  = img.fromImage(img.toImage().scaled(size(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
    QPalette palette;
    palette.setBrush(backgroundRole(), bkPixmap);
    setPalette(palette);

    // Qt3
    //setPaletteBackgroundPixmap(img.fromImage(img.toImage().scaled(size(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation)));
}

void ICQPicture::setPict(QImage &img)
{
    if (img.isNull()){
        lblPict->setText(i18n("Picture is not available"));
        return;
    }
    QPixmap pict;
    pict.fromImage(img);
    lblPict->setPixmap(pict);
    lblPict->setMinimumSize(pict.size());
}

// experimental
QPixmap PrintLayout::convertPixmapToGrayscale(QPixmap pixmap) const
{
    QImage image = pixmap.toImage();
    int gray, width = pixmap.width(), height = pixmap.height();
    for (int i = 0; i < width; i++) {
        for (int j = 0; j < height; j++) {
            gray = qGray(image.pixel(i, j));
            image.setPixel(i, j, qRgb(gray, gray, gray));
        }
    }
    return pixmap.fromImage(image);
}

来自：https://cpp.hotexamples.com/zh/examples/-/QPixmap/fromImage/cpp-qpixmap-fromimage-method-examples.html

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