Re: [libreoffice-users] Writer's A4 page pixel dimensions

Dave Koelmeyer wrote:
> Hi All,
>
> I'm creating full A4-sized page background images in GIMP to insert into
> A4-format Writer documents. I've noticed that when these images are
> added to Writer and anchored to page, things are not perfectly flush as
> I would expect.
>
> After a bit of tinkering I believe this is because Writer doesn't treat
> an A4-format page as having exactly 2480x3508 pixel dimensions (at 300 DPI).
>
> For example, my GIMP working files use the A4 300 DPI preset, which is
> 2480x3508 pixels. If I create a new blank Writer document using A4 page
> size, then export this blank document as a PNG and set the export DPI
> setting to 300, Writer instead displays this as 2481x3507 pixels. I see
> similar ever-so-slightly different results when attempting to import an
> A4 PDF exported from Writer into GIMP at 300 DPI, again off by a matter
> of pixels.
>
> Everything I've read points to 2480x3508 definitely being the dimensions
> for A4 (e.g. http://www.a4papersize.org/a4-paper-size-in-pixels.php).
> Can someone please help me understand why there is a difference in Writer?

Probably differences in rounding. An A4 page isn't exactly 2480 x 3508 
pixels at 300 dpi. A4 is 210mm x 297mm.
  210mm / 25.4mm/in * 300dpi ~= 2480.3 pixels
  297mm / 25.4mm/in * 300dpi ~= 3507.9 pixels
Rounding that to 2481 x 3507 does seem a bit odd, but it looks like 
there may be some intermediate rounding in the calculation:
  210mm / 25.4mm/in ~=  8.27in;  8.27in * 300dpi = 2481 pixels
  297mm / 25.4mm/in ~= 11.69in; 11.69in * 300dpi = 3507 pixels

How are you determining the pixel sizes that LibreOffice is using for 
your image anyway? Image sizes are specified in terms of the printed 
size (mm, inches, etc.) rather than in pixels. Unless your display is 
300dpi, the image on screen will be scaled anyway.

If you're finding that the size in the image properties can't be set to 
210mm x 297mm because of the slight difference in pixel aspect ratio, 
you could try unticking the "keep ratio" box so that the size can be set 
to 210mm x 297mm.

If you've got LibreOffice set to work in inches, you might setting it to 
cm or mm when using ISO paper sizes avoids the intermediate rounding. 
Tools > Options > LibreOffice Writer > General > Measurement unit.

Mark.


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