gistfile1.txt

#!/usr/bin/env python

import math

def conv2d(r, c, data):
   length_r = min(len(r), len(data))
   length_c = min(len(c), len(data[0]))
   conv_sum = 0
   for v in range(length_r):
      for u in range(length_c):
         conv_sum += data[v][u] * r[v] * c[u]

   return conv_sum

def idct2d(data):
   length_c = len(data[0])
   length_r = len(data)

   dct_ret = [[0 for i in range(length_c)] for j in range(length_r)]

   for v in range(length_r):
      for u in range(length_c):
         cos_val_r = [math.sqrt((1.0 if y == 0 else 2.0) / length_r) * math.cos(math.pi * (v + 0.5) * y / length_r) for y in range(length_r)]
         cos_val_c = [math.sqrt((1.0 if x == 0 else 2.0) / length_c) * math.cos(math.pi * (u + 0.5) * x / length_c) for x in range(length_c)]

         dct_ret[v][u] = round(conv2d(cos_val_r, cos_val_c, data))

   return dct_ret

def dct2d(data):
   length_c = len(data[0])
   length_r = len(data)

   dct_ret = [[0 for i in range(length_c)] for j in range(length_r)]

   for v in range(length_r):
      for u in range(length_c):
         cos_val_r = [math.cos(math.pi * (y + 0.5) * v / length_r) for y in range(length_r)]
         cos_val_c = [math.cos(math.pi * (x + 0.5) * u / length_c) for x in range(length_c)]

         a_r = math.sqrt((1.0 if v == 0 else 2.0) / length_r)
         a_c = math.sqrt((1.0 if u == 0 else 2.0) / length_c)

         for i in range(len(cos_val_r)):
            cos_val_r[i] *= a_r
         for i in range(len(cos_val_c)):
            cos_val_c[i] *= a_c

         dct_ret[v][u] = conv2d(cos_val_r, cos_val_c, data)

   return dct_ret

def quantize(data, quant):
   return [[round(data[y][x] / quant[y][x]) for x in range(len(data[0]))] for y in range(len(data))]

def dequantize(data, quant):
   return [[data[y][x] * quant[y][x] for x in range(len(data[0]))] for y in range(len(data))]

data = [
      [-76, -73, -67, -62, -58, -67, -64, -55],
      [-65, -69, -73, -38, -19, -43, -59, -56],
      [-66, -69, -60, -15,  16, -24, -62, -55],
      [-65, -70, -57,  -6,  26, -22, -58, -59],
      [-61, -67, -60, -24,  -2, -40, -60, -58],
      [-49, -63, -68, -58, -51, -60, -70, -53],
      [-43, -57, -64, -69, -73, -67, -63, -45],
      [-41, -49, -59, -60, -63, -52, -50, -34]
]

quant = [
      [16, 11, 10, 16,  24,  40,  51,  61],
      [12, 12, 14, 19,  26,  58,  60,  55],
      [14, 13, 16, 24,  40,  57,  69,  56],
      [14, 17, 22, 29,  51,  87,  80,  62],
      [18, 22, 37, 56,  68, 109, 103,  77],
      [24, 35, 55, 64,  81, 104, 113,  92],
      [49, 64, 78, 87, 103, 121, 120, 101],
      [72, 92, 95, 98, 112, 100, 103,  99]
]

print("Orig:")
for row in data:
   print(row)

dct_data = dct2d(data)
dct_data = quantize(dct_data, quant)
dct_data = dequantize(dct_data, quant)
#print(dct_data)

#print("DCT:")
#for row in dct_data:
#   print(row)

orig_data = idct2d(dct_data)

print("iDCT:")
for row in orig_data:
   print(row)