[gdal-dev] Contrast, Brightness and Gamma

Saâd HESSANE saad.hessane at gmail.com
Tue Mar 20 20:30:57 EDT 2012


Thank's all for your answers.
I will use the LUT method, cause is the most right for me.

Chaitanya said : "Gamma correction is more related to displaying the data
than the data itself".
Not in my case. I have to do this correction. But how to do that? Do i
embed a VRT with a contrast correction LUT, in another VRT with a gamma
correction LUT ? Or there is a method to declare LUTs in order to execute
in the same vrt ?

Thank's again !


2012/3/20 Brent Fraser <bfraser at geoanalytic.com>

>  I like to use gdal_contrast_stretch from
> http://www.gina.alaska.edu/projects/gina-tools/
>
> Usage: gdal_contrast_stretch <src.tif> <dst.tif>
>   { { -linear-stretch <target_avg> <target_stddev> } |
>     { -percentile-range <from: 0.0-1.0> <to: 0.0-1.0> } |
>     { -histeq <target_stddev> } }
>   [ -ndv <no_data_val> ]
> Input must be either 8-bit or 16-bit.  Output is 8-bit.
>
> For example:
>
> gdal_contrast_stretch -percentile-range 0.02 0.98 input16bit.tif
> output8bit.tif
>
> Best Regards,
> Brent Fraser
>
>
> On 3/20/2012 9:55 AM, Saâd HESSANE wrote:
>
> Hi list,
>
> I use gdal_translate to convert 16bits images to 8bits images. The
> gdal_translate have the -scale argument to specify the convertion range
> (source->destination).
> If I change the destination range (dst_min and dst_max), I can do manually
> a brightness correction (also a contrast correction).
>
> But is there any way to do that with a Photoshop like method?
> For example set a brightness to -50, a contrast to +8 and let
> gdal_translate do the job ?
>
> Also can I apply a gamma correction?
>
> I saw the VRT format and there's a way to apply a LUT. But I don't think a
> LUT of 65536 values is the best way to apply the correction.
>
> Also the VRT have the scale ratio and scale offset elements. I think it
> can be useful but I don't understand how use it...
>
> So simply put, my question : can I do a contrast, brightness or gamma
> correction to a raster with gdal?
>
> Thank you !
>
> PS : I apologize for my broken English !
>
>
> _______________________________________________
> gdal-dev mailing listgdal-dev at lists.osgeo.orghttp://lists.osgeo.org/mailman/listinfo/gdal-dev
>
>
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