File:JPEG example subimage - equalized.svg
Summary
| Description | |
| Date | |
| Source |
Own work in Inkscape |
| Author | en:User:Cburnett |
| Permission (Reusing this file) |
GFDL (image); GPL (source code) |
| Other versions | Image:JPEG example subimage.svg — Non-equalized image |
Source code
I generated the normalized data by writing a simple python script:
import math
img = [
[52, 55, 61, 66, 70, 61, 64, 73],
[63, 59, 55, 90, 109, 85, 69, 72],
[62, 59, 68, 113, 144, 104, 66, 73],
[63, 58, 71, 122, 154, 106, 70, 69],
[67, 61, 68, 104, 126, 88, 68, 70],
[79, 65, 60, 70, 77, 68, 58, 75],
[85, 71, 64, 59, 55, 61, 65, 83],
[87, 79, 69, 68, 65, 76, 78, 94]
]
# Number of pixels
N = len(img) * len(img[0])
# Initialize histogram and cumulative distribution function (cdf)
hist = {}
cdf = {}
norm_cdf = {}
for i in range(255):
hist[i] = 0
cdf[i] = 0
norm_cdf[i] = 0
# Create histogram
for row in img:
for val in row:
hist[val] += 1
# Create cdf
for i in range(255):
for j in range(i+1):
cdf[i] += hist[j]
norm_cdf[i] = int(math.floor(float(cdf[i]-1)/63*255))
newimg = [
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0]
]
for i in range(8):
for j in range(8):
newimg[i][j] = norm_cdf[ img[i][j] ]
print '+-------+-----------+-----+----------------+'
print '| %5s | %9s | %3s | %14s |' % ('Value', 'Histogram', 'cdf', 'Normalized cdf')
print '+-------+-----------+-----+----------------+'
for i in range(255):
if hist[i] == 0: continue
print '| %5s | %9s | %3s | %14s |' % (i, hist[i], cdf[i], norm_cdf[i])
print '+-------+-----------+-----+----------------+'
print ''
print 'Original subimage:'
print ''
for i in range(8):
print ('%4d'*8) % tuple(img[i])
print ''
print ''
print 'Equalized subimage:'
print ''
for i in range(8):
print ('%4d'*8) % tuple(newimg[i])
Sample output:
+-------+-----------+-----+----------------+ | Value | Histogram | cdf | Normalized cdf | +-------+-----------+-----+----------------+ | 52 | 1 | 1 | 0 | | 55 | 3 | 4 | 12 | | 58 | 2 | 6 | 20 | | 59 | 3 | 9 | 32 | | 60 | 1 | 10 | 36 | | 61 | 4 | 14 | 52 | | 62 | 1 | 15 | 56 | | 63 | 2 | 17 | 64 | | 64 | 2 | 19 | 72 | | 65 | 3 | 22 | 85 | | 66 | 2 | 24 | 93 | | 67 | 1 | 25 | 97 | | 68 | 5 | 30 | 117 | | 69 | 3 | 33 | 129 | | 70 | 4 | 37 | 145 | | 71 | 2 | 39 | 153 | | 72 | 1 | 40 | 157 | | 73 | 2 | 42 | 165 | | 75 | 1 | 43 | 170 | | 76 | 1 | 44 | 174 | | 77 | 1 | 45 | 178 | | 78 | 1 | 46 | 182 | | 79 | 2 | 48 | 190 | | 83 | 1 | 49 | 194 | | 85 | 2 | 51 | 202 | | 87 | 1 | 52 | 206 | | 88 | 1 | 53 | 210 | | 90 | 1 | 54 | 214 | | 94 | 1 | 55 | 218 | | 104 | 2 | 57 | 226 | | 106 | 1 | 58 | 230 | | 109 | 1 | 59 | 234 | | 113 | 1 | 60 | 238 | | 122 | 1 | 61 | 242 | | 126 | 1 | 62 | 246 | | 144 | 1 | 63 | 250 | | 154 | 1 | 64 | 255 | +-------+-----------+-----+----------------+ Original subimage: 52 55 61 66 70 61 64 73 63 59 55 90 109 85 69 72 62 59 68 113 144 104 66 73 63 58 71 122 154 106 70 69 67 61 68 104 126 88 68 70 79 65 60 70 77 68 58 75 85 71 64 59 55 61 65 83 87 79 69 68 65 76 78 94 Equalized subimage: 0 12 52 93 145 52 72 165 64 32 12 214 234 202 129 157 56 32 117 238 250 226 93 165 64 20 153 242 255 230 145 129 97 52 117 226 246 210 117 145 190 85 36 145 178 117 20 170 202 153 72 32 12 52 85 194 206 190 129 117 85 174 182 218
Licensing
Image is licensed under the GFDL:
I, the copyright holder of this work, hereby publish it under the following licenses:
 |
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License. |
   |
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. | |
| ||
| This licensing tag was added to this file as part of the GFDL licensing update. |
You may select the license of your choice.
Source code is licensed under the GPL version 2:
I, the copyright holder of this work, hereby publish it under the following license:
 |
This work is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2. This work is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See version 2 of the GNU General Public License for more details. |
