Le 01/03/2017 à 06:57, darkta...@911networks.com a écrit :
DT 2.2.3 on arch.
I took photos of a car at night and did some light painting with an
LED in 25 seconds blocks.
I have 9 images with each image a different area of the car lit by
the LED. How can I merge them and selecting the lit section?
They are all lined up (tripod).
Is there some software that will allow me to masks them.
Gimp is a problem, it's only 8 bit and I'd like to print the image
to at least 11 by 14 and maybe 16 by 20. (the last time I tried, there
was some banding in the skys)
Hello,
Off-topic? Perhaps not so much.
First, it might not be that off-topic. Are your images raw?
You can consider the merge step being done before or after darktable
processing.
It might make sense to pre-process the images with darktable (noise
reduction etc etc) export from darktable and merge the resulting images.
Or the contrary : merge all (presumably raw) photos with brightest pixel
into a picture then process. But much software doesn't actually deal
with raw, only handle them to ufraw or similar and work on the result,
so you lose a lot of choice.
So, if you actually want to personalize the image, pre-process all
pictures very lightly with darktable, then merge, then process the
merged picture as you wish in darktable again.
You might want to ask darktable to export in a 16-bit format with linear
colorspace, for best preservation of subtle variations and avoid banding.
Simple precedent example
I had a similar need combining photos of the sky showing the ISS passing
by, appearing as a series of dashes.
ImageMagick can do it. In my case it was 8-bit JPEG, but it seems that
ImageMagick has been able to perform 16-bit processing since at least
2008, see also
http://stackoverflow.com/questions/24683912/imagemagick-depth-convert .
Merging with brightest pixel is done with "-compose lighten".
Here's the script I used: it captures all JPG files and writes a png.
TMPF=temp.miff ; convert -verbose $( ls -1b *JPG | head -n 1 ) $TMPF ;
for a in *JPG ; do echo $a ; composite -verbose $TMPF $a -compose
lighten $TMPF ; done ; convert -verbose $TMPF composite_max.png ; rm $TMPF
You can use that as a starting point, changing extensions, adding -depth
16, prefixing png with PNG48:, and using "identify" to check if files
are 8bit or 16bit.
Reference and resulting picture :
https://plus.google.com/+St%C3%A9phaneGourichon/posts/U68FCFQZhxo
Later I did something different with that result :
https://plus.google.com/+St%C3%A9phaneGourichon/posts/WbNXPoV4sqA
Regards,
--
Stéphane Gourichon
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