On Tue, 22 Sep 2020 at 16:36, Andrea Giudiceandrea <[email protected]> wrote: > > Nyall Dawson wrote > > Actually it's a bit more complex than this, because regardless of the > > DPI specified for the page, the width/height have to be specified in > > size in inches * 72! (i.e. there's a hardcoded 72 dpi assumption > > somewhere). > > Hi, > I don't know how composition.xml works, but if you wonder why in PDF page > the width/height have to be specified in "size in inches * 72" you will find > a hint in PDF 32000-1:2008 [1] especially at paragraphs 7.7.3.3 Page > Objects, Table 30 and 8.3 Coordinate Systems. > > "The length of a unit along both the x and y axes is set by the UserUnit > entry (PDF 1.6) in the page dictionary (see Table 30). If that entry is not > present or supported, the default value of 1⁄72 inch is used. This > coordinate system is called default user space" > > "Note 2: The default for the size of the unit in default user space (1⁄72 > inch) is approximately the same as a point, a unit widely used in the > printing industry. It is not exactly the same, however; there is no > universal definition of a point." > > "UserUnit: A positive number that shall give the size of default user space > units, in multiples of 1⁄72 inch. The range of supported values shall be > implementation-dependent. Default value: 1.0 (user space unit is 1⁄72 > inch)." > > See also [2] and [3].
Thanks Andrea! So then my question would be why the PDFs attached to https://github.com/qgis/QGIS/issues/33465 are showing incorrect page sizes in Acrobat Reader, when it appears as though GDAL is correctly generating them! Have you any ideas why this could be occurring? Nyall > > Hope this will help. > > Best regards. > > Andrea Giudiceandrea > > > [1] > https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/PDF32000_2008.pdf > [2] https://stackoverflow.com/a/21164534/8779560 > [3] https://github.com/qgis/QGIS/issues/33465#issuecomment-644566633 > > > > -- > Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html > _______________________________________________ > gdal-dev mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
