[FWTools] gdal translate - air photo seems washed out after converting image

[Richard Greenwood]

On Wed, Jul 10, 2013 at 3:08 PM, Mark Volz <MarkVolz at co.lyon.mn.us> wrote:

> Hello,
>
> I converted a mr sid air photo to a tif file.  The colors appear washed
> out and too bright compared to the mr sid file.
>
>
> I would like to create an image file that has the following three
> characteristics:
>
> 1) Fast for Mapserver to read.
> 2) Relatively the same size as the MrSID file.  - I would prefer a file
> size that is no larger than twice the size of the Mr SID file, even if it
> means that I have to take a small hit by using compression
> 3) retains the same image quality as the original MrSID file
>
> The following two commands made the image fast for mapserver, and
> relatively small.  But the colors were washed out...
>
> c:\ms4w\apps\PipestoneMaps\Raster\Picto2013>gdal_translate -CO TILED=YES
> -CO PHOTOMETRIC=YCBCR -CO TFW=YES -CO COMPRESS=JPEG -CO BIGTIFF=YES
> MNPIPE13-SID-9INCH.sid New.tif
> c:\ms4w\apps\PipestoneMaps\Raster\Picto2013>gdaladdo -r average --config
> compress_overview JPEG --config photometric_overview YCBCR New.tif 2 4 8 16
> 32 64 128 256
>
>
> What can I do to improve the image quality, while retaining the speed and
> a moderate file size?
>
> Thanks
>
> Mark Volz, GISP
> GIS Specialist
>


Mark,

Those are pretty much the commands that I regularly use to prepare imagery
for mapserver. I have never experienced any noticeable color distortion.
What does it look like with a straight
   gdal_translate MNPIPE13-SID-9INCH.sid New.tif
obviously that's not what you want for a final product, but it would be my
first step toward 'debugging' the problem.

Rich


-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com
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