Image Processing Basics - Digital Signal Processing: Fundamentals and Applications - page 690

After rounding, it follows that

2
4

3
5 ¼ round

2
4

3
5 ¼

2
4

3
5

R
G
B

199:53
10:16
99:9

200
10
100

EXAMPLE 14.3
Given the 2 2 RGB image

" 100 50
200 150

# " 10 25

20 50

# " 10 5

20 15

#

R ¼ G ¼ B ¼

convert the RGB color image into a grayscale image.
Solution:
Since only Y components are kept in the grayscale image, we apply Equation (14.4) to each pixel in the 2 x 2 image
and round the results to integers as follows:

" 100 50
200 150

# " 10 25

20 50

# " 10 5

20 15

# " 37 30

74 76

#

Y ¼ 0:299 þ 0:587 þ 0:114 ¼

Figure 14.9 shows the grayscale image converted from the 24-bit color image in Figure 14.5 using
the RGB-to-YIQ transformation, where only the luminance information is retained.

14.1.6 MATLAB Functions for Format Conversion
The following list summarizes MATLAB functions for image format conversion:
imread ¼ read image data file with the specified format
X ¼ 8-bit grayscale image, 8-bit indexed image, or 24-bit RGB color image

FIGURE 14.9
Grayscale image converted from the 24-bit color image in Figure 14.5 using RGB-to-YIQ transformation.