rgb2pct.py increases size of file 20 fold!

Question

I wanted to reduce the number of bands of a tif file from 3 to 1...

I used this command

rgb2pct.py -n 256 fnp_braunschweig.tif fnp_bs.tif

and it increased the size from 31mb to 778mb

I actually want to decrease the size of the file.

Why is this happening?

Jason Scheirer · Accepted Answer · 2012-02-22 20:18:03Z

6

The output Tiff is likely not using compression, hence the larger file size. Use the gdal_translate command, something along the lines of this:

gdal_translate -of GTiff -co "COMPRESS=DEFLATE" -b N fnp_braunschweig.tif fnp_bs.tif

where N is the band number you want to keep. The options for compression are NONE, LZW, PACKBITS, JPEG, CCITTRLE, CCITTFAX3, CCITTFAX4, DEFLATE.

answered Feb 22, 2012 at 20:18

Jason Scheirer

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1

Especially note the -co "COMPRESS=DEFLATE" and -co "PHOTOMETRIC=YCBCR" if appropriate. Use gdalinfo to determine what the compression settings of the original tiff were and use creation options from gdal.org/frmt_gtiff.html appropriately.
– Howard Butler
Commented Feb 23, 2012 at 14:05
thanks. how can I compress three bands into one? I don´t want to pick either red,green, or blue, I just want to compress them into one.
– Robert Buckley
Commented Feb 23, 2012 at 21:16

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