Image Acquisitionand Proces

Image Processing 123
For example, the image below contains a glare spot, where incident light
has reßected from a glossy surface, creating a blind spot. Equalization can be
used to enhance the image, effectively stretching the equalization range to cover
the complete intensity range, making it much easier to read the underlying text.
The equalization example in Figure 5.55 was achieved using the code shown in
Figure 5.56.
FIGURE 5.56 Equalization example — wiring diagram.
TABLE 5.3
Item
Minimum
Maximum
Description
The minimum value is the smallest intensity to use during equalization. After the
equalization is complete, all pixel values that are less than or equal to the minimum
in the original image are set to 0 for an 8-bit image. In 16-bit and ßoating-point
images, these pixel values are set to the smallest pixel value found in the original
image.
The maximum value is the highest intensity to use during equalization. After the
equalization is complete, all pixel values that are greater than or equal to the
maximum in the original image are set to 255 for an 8-bit image. In 16-bit and
ßoating-point images, these pixel values are set to the largest pixel value found
in the original image.
The equalization range is a cluster containing the elements described in Table
5.3. Equalization can also be used to remove background data when an object’s
intensities are very different from that of the background (Figure 5.57). Notice that
the background is completely removed and the contrast of the leaves has been
increased.