### Histogram Equalization
Enhances image contrast by equalizing its histogram.
**Example:** Equalize a 2x2 image: [[10,20],[30,40]] becomes [[0,50],[100,150]].
**Constraints:** Image size: 2x2 to 10x10, pixel values: 0-255.
Test Cases
Test Case 1
Input:
[[10,20],[30,40]]Expected:
[[0,50],[100,150]]Test Case 2
Input:
[[50,100],[150,200]]Expected:
[[0,100],[150,255]]+ 3 hidden test cases