Midterm Exam 1 Review Sp2005

1. If you don't post, neither will I. I will not be posting official solutions to these problems at all! If one of you gets it right, terrific!
2. I will try to always point out if an answer is wrong. I won't always point out when the answer is right.
3. I am glad to work with you toward the right answer. I will give hints, and I'm glad to respond to partial guesses.

• Mark Guzdial

What do they do?

> Picture p = new Picture("D:/cs1316/MediaSources/Swan.jpg"); 
> p.methodA(); p.show(); // Then methodB and methodC 

  public void methodA(){
    Pixel p;
    for (int x=0; x < this.getWidth(); x++)
    {for (int y = 0; y < this.getHeight(); y++)
      {
      p=this.getPixel(x,y);
      p.setRed(255-p.getRed());
      p.setGreen(255-p.getGreen());
      p.setBlue(255-p.getBlue());
    }}}
  
    public void methodB(){
    Pixel p;
    for (int x=(int) (this.getWidth()/2); x < this.getWidth(); x++)
    {for (int y = 0; y < this.getHeight(); y++)
      {
      p=this.getPixel(x,y);
      p.setRed(255-p.getRed());
      p.setGreen(255-p.getGreen());
      p.setBlue(255-p.getBlue());
    }}}

    public void methodC(){
    Pixel p;
    for (int x=0; x < this.getWidth(); x++)
    {for (int y = 0; y < this.getHeight()/2; y++)
      {
      p=this.getPixel(x,y);
      p.setRed(255-p.getRed());
      p.setGreen(255-p.getGreen());
      p.setBlue(255-p.getBlue());
    }}}

Properties and Data Structures

Flip, the other way.

  /**
   * Method to flip an image left-to-right
   **/
  public Picture flip() {
    
    Pixel currPixel;
    Picture target = new Picture(this.getWidth(),this.getHeight());
    
    for (int srcx = 0, trgx = getWidth()-1; srcx < getWidth(); srcx++, trgx--)
    {
      for (int srcy = 0, trgy = 0; srcy < getHeight(); srcy++, trgy++)
      {
        // get the current pixel 
        currPixel = this.getPixel(srcx,srcy);
        
        /* copy the color of currPixel into target
         */
        target.getPixel(trgx,trgy).setColor(currPixel.getColor());
      }
    };
    return target;
  }

Posterize

• If red is greater than 128, make it 255
• If red is less than or equal to 128, make it 5
• If blue is less than or equal to 250, make it 200
• If blue is greater than 250, make it 201
• If green is less than 10, make it 200.
• If green is greater than 200, make it 10. Leave other values of green alone

  /**
   * Method to posterize (reduce the number of colors) in the picture
   * The number of reds, greens, and blues will be 4
   */
  public void posterize()
  {
    Pixel pixel = null;
    int redValue = 0;
    int greenValue = 0;
    int blueValue = 0;
    
    // loop through the pixels
    for (int x = 0; x < this.getWidth(); x++) {
      for (int y = 0; y < this.getHeight(); y++) {
        
        // get the current pixel and colors
        pixel = this.getPixel(x,y);
        redValue = pixel.getRed();
        greenValue = pixel.getGreen();
        blueValue = pixel.getBlue();
        
        // check for red range and change color
        if (redValue < 64)
          redValue = 31;
        else if (redValue < 128)
          redValue = 95;
        else if (redValue < 192)
          redValue = 159;
        else 
          redValue = 223;
        
        // check for green range
        if (greenValue < 64)
          greenValue = 31;
        else if (greenValue < 128)
          greenValue = 95;
        else if (greenValue < 192)
          greenValue = 159;
        else
          greenValue = 223;
        
        // check for blue range
        if (blueValue < 64)
          blueValue = 31;
        else if (blueValue < 128)
          blueValue = 95;
        else if (blueValue < 192)
          blueValue = 159;
        else
          blueValue = 223;
        
        // set the colors
        pixel.setRed(redValue);
        pixel.setGreen(greenValue);
        pixel.setBlue(blueValue);
      }
    }
  }

Turtle Initial

public class MyTurtlePicture {
  
  public static void main(String [] args) {
    
    FileChooser.setMediaPath("D:/cs1316/MediaSources/");
    Picture canvas = new Picture(600,600);
    Turtle jenny = new Turtle(canvas);
    Picture lilTurtle = new Picture(FileChooser.getMediaPath("Turtle.jpg"));
    
    for (int i=0; i <=40; i++)
    {
      if (i < 20)
      {jenny.turn(20);}
      else
      {jenny.turn(-20);}
      jenny.forward(40);
      jenny.drop(lilTurtle.scale(0.5));
    }
    
    canvas.show();
  }
  
}

Short Essay

Link to this Page

• Exam Reviews last edited on 4 December 2007 at 9:14 pm by c-76-17-114-206.hsd1.ga.comcast.net