0.3 Pr0130-introduction to image processing algorithms  (Page 22/3)

Table of contents

• Preface
  • Viewing tip
    • Images
    • Listings
• Preview
  • Deduce the algorithm
  • I mplement the algorithm
  • Program output
  • The algorithm
    • Obvious that the blue color value is reduced to zero
    • Color inversion is not quite so obvious
• Discussion and sample code
  • Will explain in fragments
  • The driver class named Pr0130a
  • The runner class named Pr0130aRunner
• Run the program
• Summary
• What's next?
• Miscellaneous
• Complete program listing

Preface

This module is one in a collection of modules designed to teach you about the Processing open source programming environment.

Processing is a Java-based OOP programming environment for people who want to create images, animations, and interactions.

The purpose of this module is to introduce you to pixel-based image processing algorithms, similar to those that you might find in commercial imageediting software such as Photoshop .

Click here to view the JavaScript version of the sketch discussed in this module in your HTML 5compatible browser.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the imagesand listings while you are reading about them.

Images

• Image 1 . The raw image displayed in an image explorer.
• Image 2 . The modified image displayed in an image explorer.

Listings

• Listing 1 . Copy pixel colors from the input image to the display image.
• Listing 2 . The remainder of the for loop.
• Listing 3 . The remainder of the run method.
• Listing 4 . Class Pr0130a.
• Listing 5 . Class Pr0130aRunner.

Preview

The program that I will explain in this module is designed to be used as a preliminary test of the student's understanding of programming using Java and Processing Development Environment (PDE) .

If this were a real test, the student would be provided an image file named Pr0130a.jpg along with a pair of stand-alone Processing applications. Those applications would produce the raw image and a modifiedversion of the raw image, each in an image explorer, as shown in Image 1 and Image 2 . (Click here to view the modified image version of the sketch in your HTML 5 compatiblebrowser.)

Deduce the algorithm

The first requirement would be for the student to examine the raw image shown in the image explorer window in Image 1 and to deduce the algorithm required to transform that image into the modified image shown inthe image explorer window in Image 2 .

Implement the algorithm

The second requirement would be for the student to implement the algorithm once it is established. Among other things, this would require that thestudent be able to:

• Load an image from an image file.
• Modify the pixels in the image according to the algorithm.
• Write one sketch to display the raw image in an image explorer window before it is modified.
• Write another sketch to display the modified image in another image explorer window after it is modified.