[gdal-dev] translating palettes in geotiff - followup

[David Strip]

In my previous email, I laid out a process that seems to work for me. 
Now I realize that while this works for a single input file, how do I 
generalize it to work on a set of tiles?
At first I naively thought I could just replace the SourceFileName and 
re-run the gdal_translate -of gtiff step, but since the location is 
embedded in the vrt, every tile would end up in the same place.
How do I generalize this process so I can reuse the edits to the .vrt?

On 4/23/2013 3:20 PM, David Strip wrote:
> From Even's advice, I was able to piece together this workflow.
> Given an input geotiff  image.gtif
> gdaltranslate -of image.gtif image.vrt
>
> Then open image.vrt in a text editor and look for the color table by 
> searching for the tag <ColorTable> (actually you probably don't need 
> to search, it's near the top)
> Replace the contents of the color palette with the palette entries you 
> want on output.
>
> Then below the color table look for <SimpleSource> and replace it with 
> <ComplexSource>
> Look for </SimpleSource> and replace with <ComplexSource>
> Add a new line above </ComplexSource> that looks like
> <LUT>input_color_index:output_color_index, 
> input_color_index:output_color_index, ... </LUT>
> for example if you want to map input palette entry 1 to output entry 
> 10, input 3, to output 5, ...
> <LUT>1:10, 3:5, ...<LUT>
> You will need to map EVERY input color that occurs in your image to an 
> output color or else gdal_translate will interpolate a color for you, 
> and you don't want that.
> Now that you've edited the file run
> gdal_translate -of gtiff image.vrt mapped_image.gtif
>
> And you're done.
>
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