📊 Histogram Equalization Visualizer
Upload an image and explore grayscale conversion, histogram analysis,
histogram equalization and its mathematics.
Please upload an image to begin.
3. Grayscale Histogram
4. Histogram Values
| Gray Level |
Frequency |
Probability |
CDF |
New Gray Level |
6. Histogram After Equalization
🧮 Histogram Equalization Mathematics
Step 1: Find the frequency
For every grayscale intensity rk,
count how many pixels have that intensity.
nk = Number of pixels having intensity rk
Step 2: Calculate probability
Let n be the total number of pixels.
p(rk) =
nk / n
Step 3: Calculate cumulative distribution function (CDF)
CDF(rk) =
Σ p(rj)
for j = 0 to k
The CDF adds the probabilities from the first gray level
up to the current gray level.
Step 4: Histogram equalization formula
sk =
(L - 1) × CDF(rk)
Where:
- L = number of possible gray levels
- For an 8-bit image, L = 256
- Therefore L − 1 = 255
- rk = original gray level
- sk = new equalized gray level
Step 5: Example calculation
Suppose an intensity level has:
CDF = 0.60
For an 8-bit image:
s = 255 × 0.60
s = 153
Therefore, the original gray level is mapped to approximately
gray level 153.
Complete process
Image → Grayscale → Histogram → Probability →
CDF → Mapping → Equalized Image