I ran into a small limitation of rgb2pct.py when processing the
http://www.glcf.umd.edu/data/landcover/data.shtml 1km AVHRR landcover data set.
Essentially the data is structured such that there is a single color channel in
which each pixel has a value between 0 - 14. Where 0 is water and 1-4 are
forest etc.
At any rate, I needed a way to map those values to colors so I wanted to
paletize the image. I of course tried rgb2pct.py but it only supported rgb
images. So I set out to overcome this with a short hack to the script. I wasn't
sure where to post this so I'm trying th is mailing list in case someone might
want it in the repositor.
Anyway I've attached my modified version of the script to this post.
Thanks to the creators/contributers of gdal for these awesome resources!
#!/usr/bin/env python
#******************************************************************************
# $Id: rgb2pct.py 18952 2010-02-28 11:59:53Z rouault $
#
# Name: rgb2pct
# Project: GDAL Python Interface
# Purpose: Application for converting an RGB image to a pseudocolored image.
# Author: Frank Warmerdam, warmer...@pobox.com
#
#******************************************************************************
# Copyright (c) 2001, Frank Warmerdam
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
# DEALINGS IN THE SOFTWARE.
#******************************************************************************
try:
from osgeo import gdal
except ImportError:
import gdal
import sys
import os.path
def Usage():
print('Usage: rgb2pct.py [-n colors | -pct palette_file] [-of format] source_file dest_file')
sys.exit(1)
# =============================================================================
# Mainline
# =============================================================================
color_count = 256
format = 'GTiff'
src_filename = None
dst_filename = None
pct_filename = None
gdal.AllRegister()
argv = gdal.GeneralCmdLineProcessor( sys.argv )
if argv is None:
sys.exit( 0 )
# Parse command line arguments.
i = 1
grey = False
while i < len(argv):
arg = argv[i]
if arg == '-of':
i = i + 1
format = argv[i]
elif arg == '-n':
i = i + 1
color_count = int(argv[i])
elif arg == '-pct':
i = i + 1
pct_filename = argv[i]
elif arg =='-grey':
grey = True
elif src_filename is None:
src_filename = argv[i]
elif dst_filename is None:
dst_filename = argv[i]
else:
Usage()
i = i + 1
if dst_filename is None:
Usage()
# Open source file
src_ds = gdal.Open( src_filename )
if src_ds is None:
print('Unable to open %s' % src_filename)
sys.exit(1)
if grey == False and src_ds.RasterCount < 3:
print('%s has %d band(s), need 3 for inputs red, green and blue.' \
% (src_filename, src_ds.RasterCount))
sys.exit(1)
# Ensure we recognise the driver.
dst_driver = gdal.GetDriverByName(format)
if dst_driver is None:
print('"%s" driver not registered.' % format)
sys.exit(1)
# Generate palette
ct = gdal.ColorTable()
if pct_filename is None:
err = gdal.ComputeMedianCutPCT( src_ds.GetRasterBand(1),
src_ds.GetRasterBand(2 if grey == False else 1),
src_ds.GetRasterBand(3 if grey == False else 1),
color_count, ct,
callback = gdal.TermProgress,
callback_data = 'Generate PCT' )
else:
pct_ds = gdal.Open(pct_filename)
ct = pct_ds.GetRasterBand(1).GetRasterColorTable().Clone()
# Check palette is legal for grey scale image (each channel of a given color is the same value, ignore alpha)
if grey == True:
for i in range(0, ct.GetCount()):
c = ct.GetColorEntry(i)
if c[0] != c[1] or c[0] != c[2]:
print('Non-greysacle color "%s" found in pct but provided image was greyscale.')
sys.exit(1)
# Create the working file. We have to use TIFF since there are few formats
# that allow setting the color table after creation.
if format == 'GTiff':
tif_filename = dst_filename
else:
tif_filename = 'temp.tif'
gtiff_driver = gdal.GetDriverByName( 'GTiff' )
tif_ds = gtiff_driver.Create( tif_filename,
src_ds.RasterXSize, src_ds.RasterYSize, 1)
tif_ds.GetRasterBand(1).SetRasterColorTable( ct )
# ----------------------------------------------------------------------------
# We should copy projection information and so forth at this point.
tif_ds.SetProjection( src_ds.GetProjection() )
tif_ds.SetGeoTransform( src_ds.GetGeoTransform() )
if src_ds.GetGCPCount() > 0:
tif_ds.SetGCPs( src_ds.GetGCPs(), src_ds.GetGCPProjection() )
# ----------------------------------------------------------------------------
# Actually transfer and dither the data.
err = gdal.DitherRGB2PCT( src_ds.GetRasterBand(1),
src_ds.GetRasterBand(2 if grey == False else 1),
src_ds.GetRasterBand(3 if grey == False else 1),
tif_ds.GetRasterBand(1),
ct,
callback = gdal.TermProgress,
callback_data = 'Generate PCT' )
tif_ds = None
if tif_filename != dst_filename:
tif_ds = gdal.Open( tif_filename )
dst_driver.CreateCopy( dst_filename, tif_ds )
tif_ds = None
gtiff_driver.Delete( tif_filename )
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