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Compression and sizes for chain of rasters

Question asked by modybsystematics-co-il-esridist Employee on Nov 29, 2016

What will happen if I take a tif raster and copy it (using CopyRaster) a few times in a chain

CopyRaster from orig.tif to a1.tif

CopyRaster from a1 to a2.tif

CopyRaster from a2 to a3.tif

 

I use JPEG 75% as the compression for all out rasters.

Will the copy from a1 to a2 make the raster smaller and loss some values?

Can compression of JPEG on top of raster that is already compressed in JPEG change the raster and it's size?

Should I use lossless compression and in what step?

In my testing a1 and a2 was very close in size but there was some differences in pixel values.

When I used LZW to create a3 it was much bigger.

My temporary conclusion is that you need LZW until creating the final raster but this makes the middle steps of the chain slower and creates bigger temporary rasters on disk.

 

In my case it's not a chain of CopyRaster but a few other commands (SplitRaster etc.)

 

Thanks

Mody

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