Saâd, Can you provide the vrt file and the commands you used?
On Thu, Mar 22, 2012 at 11:22 PM, Saâd HESSANE <[email protected]>wrote: > 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 >> > > -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E
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