After gray-scale transformation, median filter with mask 3x3 will be carried out to
remove the noise of the image. The reason to choose mask 3x3 as it is the most suitable
mask for preprocessing of license plate. The comparison between two different masks
will be shown in Table 3.1. The higher the value of size of masks, the resolution of image
will be closer to the median of the masks. It will make the similar colour on the image to
mix together. The median filter is normally used to reduce speckle noise and salt and
pepper noise in an image. The mean filter is a simple sliding-window spatial filter that
replaces the center value in the window with the average of all the pixel values in the
kernel matrix window. Figure 3.4 shows the concept of the median filter, Figure 3.5
shows the steps in applying the median filter algorithms while Figure 3.6 shows the
pseudocode for median filter with mask 3x3. Table 3.1 shows the comparison between
two different masks