Hello,
QGIS usually uses 24bit colours using three bands with values between 0
and 255. An alpha channel can be added, if the file format supports it
(JPG does not).
If you want to save bandwidth, you can use paletted colours with
Raster -> Conversion -> RGB to PCT
allowing 256 colours or less in one band with values between 0 and 255,
and additional palette information (colour table) in the file header.
In GDAL, RGB2PCT.bat does the same, but not gdal_translate.
gdal_translate -expand rgb does only the other way round: from palette
to three bands.
HTH,
André Joost
Am 13.02.2015 um 21:38 schrieb Gabriel Lema:
Hello,
I was wondering what QGIS does to display 16 bit per channel RGB
images. I would like to covert them to 8 bit per channel normal PNG or
JPG image, but when I save it using the "Save as..." in the "Project"
menu, I get a low resolution image.
If I could have access to the conversion from 16 bit to 8 bit that
QGIS does, which makes a good looking RGB image, I could do that same
conversion on any other software, and save it full resolution. Is it a
gamma correction? I've tried many different, but haven't been
successful so far.
If I save it using gdal_translate I get a greenish looking image, that
is very different from the good looking image that QGIS displays.
Thank you for your help.
Gabriel
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