On Wednesday, 5 August 2020 16:08:13 GMT Ralph Corderoy wrote:
> Whilst all this clicking means you're learning Gimp, and it could
> instead be coded in Python using the Python Imaging Library we keep
> referring to, there's also Netpbm from the shell.
>
> wget -q -O lenna.png \
> https://upload.wikimedia.org/wikipedia/en/7/7d/
Lenna_%28test_image%29.png
>
> w=128 h=128 # Desired size.
> pngtopnm lenna.png |
> pamscale -xyfit $w $h |
> pnmpad -w $w -h $h |
> pnmremap -mapfile=<(pamseq 1 15) |
> pnmtopng >lenna-grey.png
Ralph,
I've been having a few problems reproducing my early success using The Gimp to
convert my images (I did document it, but I must have left something out).
Anyway, I thought I would give your bash code a try. I found and fixed an
error; pamscale doesn't exist, but pnmscale does but I still can't make it
work. When execution reaches the penultimate line I get the error:
./scale: line 5: pamseq: command not found
followed by a couple of EOF errors that I assume are caused by the pnmremap
failure.
I've had a good rummage and can't find a package that provides pamseq. Can you
tell me how to fix this?
Also. I assume that 'pamseq 1 15' is telling pnmremap to change the image
colormap to 16 levels. I would have expected the numbers to be 0 & 15 or 1 &
16. Any reason why 1 & 15 are used?
--
Terry Coles
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