[gdal-dev] Contrast, Brightness and Gamma

[Brent Fraser]

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!
>
>
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