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I'm using Libre Office Draw 7.6 on Windows 10 Pro.

When I use LOD to open a pdf and then export a bmp file measuring 4500 x 3600 ppi, for some reason the ppi resolution decreases to 1800 x 1440.

How can I make sure that LOD's ppi settings for exporting as a bmp work properly?

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  • Yes, I know PDFs don't use PPIs as such, because it depends how big you print them. But if you print them at the assigned size (as I will, which for this doc is a width of 15in) then PPI is literal. The original PDF used 4500. When you export from LOD as a BMP you can modify either the nominal physical dimensions in e.g. cm or the resolution in PPI. When I do the latter to 300 ppi then I'm only getting a width of 1800px. Zoom and it's clear the resolution has degraded.
    – tell
    Commented Nov 10, 2023 at 11:07

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I dont think you are likely to achieve a good outcome using Office based applications. this applies to Ms office just as much to Libre Office or most others I have worked with.

PDF conversions by non compliant PDF rendering systems (and that includes some major players such as Firefox or Google docs and HTML renderings) will assume a screen resolution of 96dpi or 72dpi for import so even if you export at 300 the result will be "fuzzy".

to put that into perspective I generated a pixel perfect 4500x3600 image and used LOD import where it is imported as if 96 dpi (it would not matter and be just the same even if using some other Well known graphics apps).

The image on the left is the original. and for comparison I exported the BMP at 4500x3600 by upscale 3.125 (300/96) and deliberatly used that for a new PDF to make a comparison on the right.

I used as many equivalents as possible to ensure the round trip was closest and what happens is here.

enter image description here

Noticeably there is often a pixel shift such that part of the left edge is not present in the right hand copy (minor issue to loose 1 pixel width, but for a grid or graticule can be critical)

More importantly the size gets bloated by the anti-alias effects.

Most importantly the true resolution of artwork is lost.

By comparison an image based graphics app at similar zoom will usually see it like this enter image description here

But retain Pixels as per one by one placements. enter image description here

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