3.17 Java3016: green-screen processing  (Page 5/6)

Very similar to earlier methods

This method is very similar to other methods that I have explained in earlier modules that use nested for loops to draw one image onto another image.

The one new thing...

The only thing that is really new in Listing 5 is the if statement that tests the color of source image pixels for a value of exactly Color.GREEN . If the color of the source pixel does not match that color exactly, it is drawn on the destination image replacing the pixel colorpreviously at that location on the destination image.

If the source pixel color does exactly match that color, it is not drawn on the destination image thereby leaving the color of the corresponding destinationpixel unchanged.

Listing 5 signals the end of the greenScreenDraw method.

The weather forecast on television

This is roughly how the TV stations superimpose a human weather forecaster onto a giant animated weather map. The forecaster is photographed with avideo camera standing in front of a green or blue screen. At the same time, an animated video of the weather map is also created.

Then each video frame of the forecaster is superimposed onto a video frame of the weather map. The green or blue pixels in the forecaster frame are notcopied onto the weather map frame. This allows the weather map pixels to show with the exception of those that are replaced by the pixels that comprisethe human forecaster. (The forecaster must be careful to avoid wearing clothing that matches the color of the green or blue screen.)

Returning to the run method

When the third call to the greenScreenDraw method returns in Listing 4 , the run method:

• Adds the student's name to the snow scene picture.
• Displays the snow scene picture (see Figure 5 ).
• Displays information about the snow scene picture on the command line screen.

The end of the program

Then the run method in Listing 4 returns control to the main method in Listing 1 causing the program to terminate.

Run the program

I encourage you to copy the code from Listing 6 . Compile the code and execute it. Experiment with the code, making changes, andobserving the results of your changes. Make certain that you can explain why your changes behave as they do.

Click the following links to download the required input images:

1. Prob03a.bmp
2. Prob03b.bmp
3. Prob03c.bmp
4. Prob03d.jpg

Summary

In this module, you learned how to write a program to do green-screen processing to superimpose a source image onto a destination image while makingthe green background of the source image appear to be transparent.

What's next?

You will learn how to darken, brighten, and tint the colors in a Picture object in the next module.

Online video links

While not a requirement of the course, you can select the following links to view optional online video lectures on the material in thismodule.

• ITSE2321 Lecture 08
  • Part01
  • Part02
  • Part03

Miscellaneous

This section contains a variety of miscellaneous information.