Making a tri-effect picture with Java

Question

I am in a Java course that features a lot of manipulation of images. An assignment that I recently could not complete involved making a picture where the effect changed from the top third to the middle third and the bottom third. So the grayscale effect I would have in the top third would become a negative effect in the middle and a color third in the bottom. The due date has come and gone, so I was hoping someone could suggest how this is done for my reference in the future. I am including my code for the negative and the grayscale below...thanks. The points are a lost cause but I'd still like to know.

Public void greyscale(int start, int end)
  {
    //creates pixel array
  Pixel[] pixelArray = this.getPixels();
  //iterates through array
    for (Pixel currPixel : pixelArray)
    {//accessor
      int green = currPixel.getGreen();
      int red = currPixel.getRed();
      int blue= currPixel.getBlue();
      double average = 0.0;

      int i = (int)start;
      //while loop to average values to create grays
      while (i < end) {
        average = ((green + blue + red)/3);
      currPixel.setGreen((int)average);
      currPixel.setRed((int)average);
      currPixel.setBlue((int)average);
      i++;
    }
     //end loop markers
  }System.out.println("Splunge.");
  } 

  public void negative(int start, int end)
  {
    //creates pixel array
  Pixel[] pixelArray = this.getPixels();
  //iterates through pixel array
    for (Pixel currPixel : pixelArray)
    {
      //accessor
      int green = currPixel.getGreen();
      int red = currPixel.getRed();
      int blue= currPixel.getBlue();

      int i = (int)start;
       //while loop to make negative pixel values
      while (i < end) {
      currPixel.setGreen(255-green);
      currPixel.setRed(255-red);
      currPixel.setBlue(255-blue);
      i++;
    }
     //end loop marker
  }System.out.println("Splunge.");
  }//end method

Answer 1 · 2016-09-28T03:15:58Z

September 28, 2016 3:15am

What are the parameters start and end supposed to mean?

That was not made clear to us.

Why are you iterating through the whole array of pixels?

I was showing that I could make a single effect for one picture to show that I could at least do that.

Did you divide a larger array into thirds elsewhere?

I have no idea how to do that. I would like to know how.

Why have the nested iterations to set the pixel to the same value n times, repeatedly?

If I don't have to, I won't. I have a decent grasp of Java fundamentals. I am not used to manipulating images. This class, so far, is almost exclusively about that use of the language. I had no idea going in. Now I am stuck and I would like not to fail.

thanks.

Nancy M.

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Nancy Melucci

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