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194 CHAPTER 6 ■ VISION

6.3 Color Processing

In the last section, we processed pixels but did not use their individual color components for
anything. To illustrate how we can use the colors of an image, we’ll threshold the colors of an
image versus the image’s greyscale. In the next few examples, I’ll threshold three colors—red,
green, and blue—for the three beverage cans.

Code Objective

The objective here is to perform a threshold operation on the three different color
components.

Code Discussion
This method is similar to thresholding except for the added parameter Color. This color is then
used to get the specific color component for the threshold. You can see from the three images
that you can almost make out which cans are red, green, and blue. See Example 6-16 and
Figures 6-13, 6-14, and 6-15.

Example 6-16. thresholdColor()
public BufferedImage thresholdColor(BufferedImage srcImg, int min, int max,
Color c) {
// get h & w
int h = srcImg.getHeight();
int w = srcImg.getWidth();
//destination image
BufferedImage dstImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
// get pixels
for (int y = 0; y < h; ++y) {
for (int x = 0; x < w; ++x) {
// get color
int srcPixel = srcImg.getRGB(x, y);
int colorValue = 0;
// get color values for color sent
if (c == null) {
colorValue = getGrey(srcPixel);
} else if (c == Color.RED) {
colorValue = new Color(srcPixel).getRed();
} else if (c == Color.GREEN) {
colorValue = new Color(srcPixel).getGreen();
} else if (c == Color.BLUE) {
colorValue = new Color(srcPixel).getBlue();
}