Normalize input 2-D Image to the range of 0-1 for double, or 0-255 for uint8
y = imnorm(x)
Input 2-D matrix
Normalized output matrix
This function is used to normalized the 2-D matrix to the range of 0-1, or 0-255 for uint8, to ensure the 2-D matrix follows the image representation standard in double or uint8 format.