I used Apple Numbers (a Spreadsheet app with styling options) to create a UX flowchart of various user interfaces of an app.
Apple Numbers has a PDF export option.
The problem is that even though some border lines in the table have been set to "none" in the export you nevertheless get small visible hairlines, see this cutout:
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Before creating a flyover video over the graphics.
My basic idea is:
So step 1, I already figured out, by these two possibilities:
convert -density 600 source.pdf export.png
But for step 2 there are so many possibilities:
resample <DPI>
or -filter <FilterName> -resize 25%
or -scale 12.5%
(when from 1200 to 150)
Please tell me by which methods (resample, resize, scale) and which of the interpolation algorithms or filters I shall use to achieve my goal of eliminating the hairlines by dissolving them into their neighboring pixels, with the rest (normal 1px lines, rendered text and symbols, etc) remaining as crisp as possible.
convert -density XXX flowchart.pdf flowchart-ImageMagick-XXX.png
a) convert -median 3x3 -resize 50% flowchart-ApplePreview-300.png flowchart-150-from-ApplePreview-300-median-3x3.png
thanks to the hint from @ChristophRackwitz
b) convert -filter Box -resize 25% flowchart-ImageMagick-600.png flowchart-150-from-ImageMagick-600-resize-box.png
Both variants are somehow good enough for my KenBurns / Dolly cam ride over them. Still I wished that there'd be an algorithm that keeps cripness but still eliminates 1px lines in very high DPI bitmaps. But I guess this is a Jack of all trades only in my phantasy.
time convert -filter Box -resize 25% 1@600.png 1@150-from-600.png
# PNG @ 39700 × 28066: 135.57s user 396.99s system 109% cpu 8:08.08 total
time convert -median 3x3 -resize 50% 2@300.png 2@150-from-300-median3x3.png
# PNG @ 19850 × 14033: 311.48s user 9.42s system 536% cpu 59.76 total
time convert -median 3x3 -resize 50% 3@300.png 3@150-from-300-median3x3.png
# PNG @ 19850 × 14033: 237.13s user 8.33s system 544% cpu 45.05 total