What are the units of QPdfDocument::pageSize?

mnbv

QPdfDocument (5.15.2) seems to not be fully documented yet.

What are the units of the size returned by pageSize()?

It appears to be some reasonable pixel-like units except I'm not sure what it's assuming the document's DPI to be. Also I've only tested on a limited set of PDF's all generated from the same source, so I'm not sure how normal my observations are, especially given it's a QSizeF rather than a QSize (which raises the possibility of e.g. other non-pixel units in other as-of-yet unencountered contexts).

Ultimately what I'd like to do is get the page size in physical units (e.g. inches) then determine a rendered output size in pixels given a user-specified DPI.

mnbv

I broke down and asked on SO, where user Mike dug into the source (which I guess I should've done).

Long story short, the size returned by pageSize() is in points, and a little further research confirmed it uses the DTP definition where 72 points = 1 inch. The results I'm seeing agree with that scaling.

#include <QCoreApplication>
#include <QDebug>
#include <QtNetwork>
#include <QtPdf>

int main (int argc, char *argv[]) {

    QCoreApplication app(argc, argv);

    QUrl url("http://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf");
    QNetworkAccessManager internet;
    QNetworkReply *reply = internet.get(QNetworkRequest(url));

    QObject::connect(reply, &QNetworkReply::finished, [reply] () {
        QPdfDocument pdf;
        pdf.load(reply);
        qDebug() << reply->url() << ":";
        for (int k = 0; k < pdf.pageCount(); ++ k)
            qDebug() << k << pdf.pageSize(k) << pdf.pageSize(k) / 72.0f;
        QCoreApplication::exit();
    });

    return app.exec();

}

Outputs:

QUrl("http://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf") :
0 QSizeF(595, 842) QSizeF(8.26389, 11.6944)

jsulm

@mnbv What Qt version do you use? I can't find anything like size() or pageSize() in https://doc-snapshots.qt.io/qt5-5.15/qpdfdocument-members.html

mnbv

@jsulm said in What are the units of QPdfDocument::pageSize?:

@mnbv What Qt version do you use? I can't find anything like size() or pageSize() in https://doc-snapshots.qt.io/qt5-5.15/qpdfdocument-members.html

@mnbv said in What are the units of QPdfDocument::pageSize?:

QPdfDocument (5.15.2) seems to not be fully documented yet.

mnbv

I broke down and asked on SO, where user Mike dug into the source (which I guess I should've done).

Long story short, the size returned by pageSize() is in points, and a little further research confirmed it uses the DTP definition where 72 points = 1 inch. The results I'm seeing agree with that scaling.

#include <QCoreApplication>
#include <QDebug>
#include <QtNetwork>
#include <QtPdf>

int main (int argc, char *argv[]) {

    QCoreApplication app(argc, argv);

    QUrl url("http://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf");
    QNetworkAccessManager internet;
    QNetworkReply *reply = internet.get(QNetworkRequest(url));

    QObject::connect(reply, &QNetworkReply::finished, [reply] () {
        QPdfDocument pdf;
        pdf.load(reply);
        qDebug() << reply->url() << ":";
        for (int k = 0; k < pdf.pageCount(); ++ k)
            qDebug() << k << pdf.pageSize(k) << pdf.pageSize(k) / 72.0f;
        QCoreApplication::exit();
    });

    return app.exec();

}

Outputs:

QUrl("http://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf") :
0 QSizeF(595, 842) QSizeF(8.26389, 11.6944)