pixval.py

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#! /usr/bin/env python
#
#
# This is a simple script based on GDAL and used to retrieve value of single raster pixel.
# It is used in WKTRaster testing to compare raster samples.
#
# Copyright (C) 2009 Mateusz Loskot <mateusz@loskot.net>
# 
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#
 
from __future__ import print_function
from osgeo import gdal
from osgeo import osr
import osgeo.gdalconst as gdalc
import struct
import sys
 
def pt2fmt(pt):
    fmttypes = {
        gdalc.GDT_Byte: 'B',
        gdalc.GDT_Int8: 'B',
        gdalc.GDT_Int16: 'h',
        gdalc.GDT_UInt16: 'H',
        gdalc.GDT_Int32: 'i',
        gdalc.GDT_UInt32: 'I',
        gdalc.GDT_Float32: 'f',
        gdalc.GDT_Float64: 'f'
        }
    if hasattr(gdalc, 'GDT_Float16'):
        fmttypes[gdalc.GDT_Float16] = 'e'
    return fmttypes.get(pt, 'x')
 
if len(sys.argv) < 5 or len(sys.argv) > 6:
    print("Usage: pixval.py <raster> <band> <x> <y>")
    print("\traster - GDAL supported dataset")
    print("\tband - 1-based number of band")
    print("\toverview - optional 1-based number of overview")
    print("\tx - Pixel column - 1..N where N is raster X dimension")
    print("\ty - Pixel row - 1..N where N is raster Y dimension")
    sys.exit(0)
 
infile = sys.argv[1]
nband = int(sys.argv[2])
x = int(sys.argv[3])
y = int(sys.argv[4])
if len(sys.argv) > 5:
    noverview = int(sys.argv[5])
else:
    noverview = None
 
print("File : %s" % infile)
print("Band : %d" % nband)
if noverview is not None:
    print("Overview: %d" % noverview)
print("Pixel: %d x %d" % (x, y))
 
ds = gdal.Open(infile, gdalc.GA_ReadOnly);
if ds is None:
    sys.exit('ERROR: Cannot open input file: ' + str(infile))
 
band = ds.GetRasterBand(nband)
if band is None:
    sys.exit('Cannot access band %d', nband)
 
if noverview is None:
    src_band = band
else:
    if noverview > 0 and noverview <= band.GetOverviewCount():
        src_band = band.GetOverview(noverview - 1)
    else:
        print("ERROR: Invalid overview index")
        print("Band %d consists of %d overivews" % (nband, band.GetOverviewCount()))
        sys.exit(1)
 
if x <= 0 or x > src_band.XSize or y <= 0 or y > src_band.YSize:
    print("ERROR: Invalid pixel coordinates")
    print("Band or overview dimensions are %d x %d" % (src_band.XSize, src_band.YSize))
    sys.exit(1)
 
# Pixel index is 0-based
pixel = src_band.ReadRaster(x - 1, y - 1, 1, 1, 1, 1)
 
fmt = pt2fmt(src_band.DataType)
pixval = struct.unpack(fmt, pixel)
 
print("Pixel value -> %s" % str(pixval[0]))