Re: [Image-SIG] Remove Noise from a National Weather Service Radar Image (.gif)

[J.D. Main]

Hey Guys,

I've got it!  Mucho thanks for the very cool numpy example from Chris and of course to everyone else for the assistance.  I can now add this code to a program that upsamples these images so they look better when plotted on a GIS map.  I realize that I'm technically destroying data by blasting pixels from the image, but sometimes it's better to have a pretty presentation!

You can try this code by grabbing a radar image from the source server:

http://radar.weather.gov/ridge/RadarImg/N0Z/

##############################################

from PIL import Image

import numpy as np

#Open the raw radar image

raw_image = Image.open("ABR_N0Z_0.gif")

# make an array out of the image:

a = np.asarray(raw_image).copy()

# The noise colors are index 0,7,8 in the palette

# I used IrfanView to determine this

noise_colors = [0,7,8]

# white is index 15

white = 15

# Replace the noise colors with white

for color in noise_colors:

    a[a==color] = white

# Build the clean image from the array

im1 = Image.fromarray(a, mode='P')

# Give it the original palette

im1.putpalette(palette)

# Save it out

im1.save("clean_image.gif")

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