Details
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Bug
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Resolution: Done
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P3: Somewhat important
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6.3.0 RC
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None
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Windows 11
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Windows
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165bc962e8 (qt/qtwebengine/dev) d379ee8735 (qt/qtwebengine/6.2) d379ee8735 (qt/tqtc-qtwebengine/6.2) 165bc962e8 (qt/tqtc-qtwebengine/dev) 165bc962e8 (qt/qtwebengine/6.4) 165bc962e8 (qt/tqtc-qtwebengine/6.4) c22aa3deb8 (qt/qtwebengine/6.3)
Description
I've been experimenting with the Qt Pdf module to render some pdf files. However, some pdf files are very slowly processed. For example running this code:
int main(int argc, char *argv[]) { QPdfDocument pdfDocument; pdfDocument.load("test3.pdf"); QElapsedTimer timer; timer.start(); auto image = pdfDocument.render(0, QSize(1000, 1000)); image.save("testimage.png"); qDebug () << QString("PDF RENDERED IN %1 ms").arg(timer.elapsed()); }
Against this pdf filetest3.pdf
Unable to embed resource: test3.pdf of type application/pdf
shows that the rendering time for the first page to a 1000x1000 QImage is around 2000ms.
Investigating this further, I decided to use pdfium directly and the following code:
int main(int argc, char *argv[]) { // initialise pdfium and ... FPDF_DOCUMENT doc = FPDF_LoadDocument("test3.pdf", NULL); QElapsedTimer timer; timer.start(); if(!doc){ qCritical() << "Cannot render page for invalid document"; } FPDF_PAGE pdfPage = FPDF_LoadPage(doc, 0); if(!pdfPage){ qCritical() << "Cannot render page because failed to load"; } QImage result(QSize(1000, 1000), QImage::Format_ARGB32); result.fill(Qt::transparent); FPDF_BITMAP bitmap = FPDFBitmap_CreateEx(result.width(), result.height(), FPDFBitmap_BGRA, result.bits(), result.bytesPerLine()); FPDF_RenderPageBitmap(bitmap, pdfPage, 0, 0, result.width(), result.height(), 0, 0); FPDF_ClosePage(pdfPage); result.save("testimage.png"); qDebug () << QString("PDF RENDERED IN %1 ms").arg(timer.elapsed()); }
gives a render time of less than 500ms, which is very strange as the code is pretty much the same as Qt Pdf module [here](https://github.com/qt/qtwebengine/blob/dev/src/pdf/qpdfdocument.cpp#L753). I've also tested the [multipage example](https://github.com/qt/qtwebengine/tree/dev/examples/pdf/multipage) included in the source of QtWebengine and enabling qt.pdf.document=true logs shows similarly high render times.
