Hy Chaitanya, I applied a LUT to the VRT. It's work fine, and all pixel are between dst_min and dst_max. But why this is not work with the -scale parameter? The doc is clear : http://www.gdal.org/gdal_translate.html. "Rescale the input pixels values from the range *src_min* to *src_max* to the range *dst_min* to *dst_max*." Is it a bug?
2012/3/22 Chaitanya kumar CH <[email protected]> > Saâd, > > It is better to have a combined LUT. It will save processing time and data > degradation. > Be informed that GDAL VRT is not specialized for this work. To get a > smooth curve as LUT, use some other graphics application that can handle > 16bit rasters. > > > On Wed, Mar 21, 2012 at 6:00 AM, Saâd HESSANE <[email protected]>wrote: > >> 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 <[email protected]> >> >>> 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 >>> [email protected]http://lists.osgeo.org/mailman/listinfo/gdal-dev >>> >>> >> >> _______________________________________________ >> gdal-dev mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/gdal-dev >> > > > > -- > Best regards, > Chaitanya kumar CH. > > +91-9494447584 > 17.2416N 80.1426E >
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