Page 238 - The Definitive Guide to Building Java Robots

Preston_5564C06.fm Page 219 Friday, September 23, 2005 5:13 AM

CHAPTER 6 ■ VISION 219

// draw line from end of direction one, to end of direction 2
Graphics2D g = img.createGraphics();
g.setColor(Color.GREEN);
g.drawLine((int)x1,(int) y1, (int) x2, (int) y2);

}

Figure 6-24. The Hough transform of the three cans

Section Summary
In this section, I used a combination of filters from pixel processing and some from Java’s
Advanced Imaging API to process images. The methods created were
• ImageProcessor.smooth(): Uses JAI to smooth an image using a low-pass filter

• ImageProcessor.sharpen(): Uses JAI to sharpen an image using a high-pass filter
• ImageProcessor.sobelGradMag(): Uses JAI to find the edges of an image
• ImageProcessor.getHoughLines(): Uses the Hough transform to find the lines in an image

• ImageProcessor.drawHoughLines(): Iterates through the Hough array to create lines on
the processed image

6.5 Chapter Summary

In this chapter, I wanted to show you how to process images from a web camera. By the final
chapter, you should be able to do some complex analysis and give your robot a lot of information
about its world using a few algorithms and data structures.
In the introduction, I created two utility classes—WindowUtilities and ExitListener—to
assist with Swing class creation. I created an ImagePanel to provide a canvas for working with
processed images and generated a sample ImageViewer that renders JPEGs.
In section 6.1, I showed you how to install and test the Java Media Framework with
FindCamera, and then created a class to get a single frame from the camera called GetFrame.
Finally, in this chapter I created a WebCamViewer to show images in real time from your webcam.