画像処理論6課題.py

import math

f = open('./mandrill.pgm', 'r')
# format
f.readline()
# size
width, height = f.readline().rstrip().split(' ')
# max
max_value = int(f.readline().rstrip())

table = [[]]

for data in f:
  for dot in data.rstrip().split(' '):
    if len(table[-1]) >= int(width):
      table.append([])
    table[-1].append(int(dot))

sobel_x = [
  [-1, 0, 1],
  [-2, 0, 2],
  [-1, 0, 1]
]
sobel_y = [
  [1, 2, 1],
  [0, 0, 0],
  [-1, -2, -1]
]
sobel_table = []
sobel_file = open('./out.pgm', 'w')
sobel_file.write('P2\n254 254\n255\n')
for y in range(1, int(height) - 1):
  sobel_table.append([])
  for x in range(1, int(width) - 1):
    diff_x = sum([sobel_x[dy][dx] * table[y - 1 + dy][x - 1 + dx] for dx in range(3) for dy in range(3)])
    diff_y = sum([sobel_y[dy][dx] * table[y - 1 + dy][x - 1 + dx] for dx in range(3) for dy in range(3)])
    diff = int(math.sqrt(diff_x ** 2 + diff_y ** 2))
    if diff > max_value:
      diff = max_value
    if diff < 0:
      diff = 0
    sobel_table[-1].append(diff)
  sobel_file.write(' '.join([str(i) for i in sobel_table[-1]]) + '\n')