Help with printing



  • Hi
    Please explain somebody how to print image with the 100% scale.
    For example this code:
    @
    QPixemap pxm = .... //load image from file
    QPrinter printer;
    QPainter painter;
    painter.begin(&printer);
    double xscale = printer.pageRect().width()/double(pxm.width());
    double yscale = printer.pageRect().height()/double(pxm.height());
    double scale = qMin(xscale, yscale);
    painter.scale(scale, scale);
    painter.drawPixmap(0,0, pxm)
    @

    Up-scale image (fit to page) to the page and this result isn't 100% image size.
    If I remove this line:
    @painter.scale(scale, scale);@

    The image will down-scale and this also isn't 100% image size.

    I understand that printer operate in QPrinter::DevicePixel space and this is (usually) a much more than screen space.
    My question is how to calculate relation between QPrinter::DevicePixel and Pixels for calculate correct scale coefficients.
    Thanks.



  • My current solution is:

    @
    QPainter painter;
    painter.begin(&m_current_printer);

    const QPixmap& pxm = ///...pixmap from file

    double prnDPI = m_current_printer.resolution();

    //ANYBODY can explain me why 72 DOI is default dpi for the most popular image editors?
    double inch_w = pxm.width() / 72.;
    double inch_h = pxm.height() / 72.;

    double img_w_pix = inch_w * prnDPI;
    double img_h_pix = inch_h * prnDPI;

    QRectF rc(0,0, img_w_pix, img_h_pix);
    painter.drawPixmap(rc, pxm, QRectF(0,0, pxm.width(),pxm.height()));
    @


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