CODEWITHSUNDEEP
pythonimagedata-sciencepgm
Nafis Islam
Nafis Islam

Reputation: 41

How to read PGM image in Python

How to read this PGM image in python? please help

PGM image link

I tried this 

import numpy as np
import matplotlib.pyplot as plt

def readpgm(name):
    with open(name) as f:
         lines = f.readlines()

    # Ignores commented lines
    for l in list(lines):
            if l[0] == '#':
            lines.remove(l)

    # Makes sure it is ASCII format (P2)
    assert lines[0].strip() == 'P2' 

    # Converts data to a list of integers
    data = []
    for line in lines[1:]:
        data.extend([int(c) for c in line.split()])

    return (np.array(data[3:]),(data[1],data[0]),data[2])

data = readpgm('514516.pgm')

plt.imshow(np.reshape(data[0],data[1])) # Usage example

it gives me this error: 

"return codecs.charmap_decode(input,self.errors,decoding_table)[0]

 UnicodeDecodeError: 'charmap' codec can't decode byte 0x90 in position 
 2075: character maps to <undefined>"

what should i do? please help

Solution:

Numpy and 16-bit PGM

Upvotes: 2

Views: 7336

Answers (1)

Mark Setchell
Mark Setchell

Reputation: 207748

Your image isn't P2 (ASCII greyscale), it is P5 (Binary Greyscale).

If you want to convert it to P2, you can use ImageMagick which is installed on most Linux distort and is available for macOS and Windows.

convert YourP5Image.pgm -compress none ActualP2Image.pgm

Or, find the Python way of reading binary NetPBM images. It is 16-bit, by the way.

Upvotes: 3

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