NDVI calculation

NDVI-calc.sh

# gets read from a database, hardwired here
NDVI_COLORMAP="006600 008800 00BB00 00FF00 CCFF00 FFFF00 FFCC00 FF8800 FF0000 EE0000 DD0000 CC0000 BB0000 AA0000 990000 880000 770000"

NIR_INPUT=nir_input.tif
NIR_OUTPUT=nir_output.tif

RED_INPUT=red_input.tif
RED_OUTPUT=red_output.tif

NDVI_IMAGE=new_ndvi.tif
NDVI_COLOR=ndvi_color.tif

python write_colormap_file.py "$NDVI_COLORMAP" custom.txt


echo "Creating NIR part of the NDVI color image for red filtered image..."
gdal_calc.py --calc="A" --A_band=1 --type=Float32 -A $NIR_INPUT --outfile $NIR_OUTPUT --NoDataValue=1.001 --overwrite


echo "Creating VIS part of the NDVI color image for red filtered image..."
gdal_calc.py --calc="A" --A_band=1 --type=Float32 -A $RED_INPUT --outfile $RED_OUTPUT --NoDataValue=1.001 --overwrite


echo "Doing the image math to create the NDVI image."
gdal_calc.py --calc="((A-B)/(A+B))" --type=Float32 -A $NIR_OUTPUT -B $RED_OUTPUT --outfile $NDVI_IMAGE --overwrite --NoDataValue=1.001


echo "Color mapping the NDVI image."
# this one creates the version with the alpha channel.  It gets up uploaded.
gdaldem color-relief $NDVI_IMAGE custom.txt $NDVI_COLOR -alpha

write_colormap_file.py

# calculate the scaling percentage to make the full res output fit inside 65000

import argparse

if __name__ == '__main__':      
    
    p = argparse.ArgumentParser (description = 'Given a colormap string, this script will generate a file to use as the colormap for gdaldem.')
    p.add_argument("colormap", type = str, help = 'Colormap String')
    p.add_argument("file_location", type = str, help = 'Target location for the generated colormap file.')

    args = p.parse_args() 

    f = open(args.file_location, 'w+')
    
    vals = [-.941, -.824, -.706, -.588, -.471, -.353, -.235, -.118, 0, .118, .235, .353, .471, .588, .706, .824, .941]
    
    # parse colormap string into list of int color values
    
    colors = []
    hexs = args.colormap.split(" ")
    
    for h in reversed(hexs):  # hexes come in positive to negative
        red = int(h[0:2], 16)
        green = int(h[2:4], 16)
        blue = int(h[4:6], 16)
        
        colors.append(str(red) + ' ' + str(green) + ' ' + str(blue))
    
    f.write('-1 ' + colors[0] + ' 255\n')
    for i in range(len(colors)):
        f.write(str(vals[i]) + ' ' + colors[i] + ' 255\n')
        
    f.write('1 ' + colors[len(colors)-1] + ' 255\n')
    f.write('nv 0 0 0 0\n')
    
    f.close()
    
    f = open(args.file_location+"x", 'w+')
    
    vals = [-.941, -.824, -.706, -.588, -.471, -.353, -.235, -.118, 0, .118, .235, .353, .471, .588, .706, .824, .941]
    
    # parse colormap string into list of int color values
    
    colors = []
    hexs = args.colormap.split(" ")
    
    for h in reversed(hexs):  # hexes come in positive to negative
        red = int(h[0:2], 16)
        green = int(h[2:4], 16)
        blue = int(h[4:6], 16)
        
        colors.append(str(red) + ' ' + str(green) + ' ' + str(blue))
    
    f.write('-1 ' + colors[0] + ' 255\n')
    for i in range(len(colors)):
        f.write(str(vals[i]) + ' ' + colors[i] + ' 255\n')
        
    f.write('1 ' + colors[len(colors)-1] + ' 255\n')
    f.write('nv 22 33 44 0\n')
    
    f.close()