April 23rd, 2015

Picture Lab – Activity 7
Mirroring pictures

Classwork:
Activity 7:
A7: Mirroring part of a picture

public void mirrorTemple()
  { 
    int mirrorPoint = 276;
    Pixel leftPixel = null;
    Pixel rightPixel = null;
    int count = 0;
    Pixel[][] pixels = this.getPixels2D();

    // loop through the rows
    for (int row = 27; row < 97; row++)
    { 
      // loop from 13 to just before the mirror point
      for (int col = 13; col < mirrorPoint; col++)
      {
        leftPixel = pixels[row][col];
        rightPixel = pixels[row][mirrorPoint - col + mirrorPoint];
        rightPixel.setColor(leftPixel.getColor());
      }
    }
   }

Questions
1. How many times would the body of this nested for loop execute?

for (int row = 7; row < 17; row++)
         for (int col = 6; col < 15; col++)

2. How many times would the body of this nested for loop execute?

       for (int row = 5; row <= 11; row++)
         for (int col = 3; col <= 18; col++)

Exercises
1. Check the calculation of the number of times the body of the nested loop executes by adding an integer count variable to the mirrorTemple method that starts out at 0 and increments inside the body of the loop. Print the value of count after the nested loop ends.

2. Write the method mirrorArms to mirror the arms on the snowman (“snowman.jpg”) to make a snowman with 4 arms. Write a class (static) test method in PictureTester to test this new method and call it in the main method.

3. Write the method mirrorGull to mirror the seagull (“seagull.jpg”) to the right so that there are two seagulls on the beach near each other. Write a class (static) test method in PictureTester to test this new method and call it in the main method.

Homework:
A8: Creating a collage

public void copy(Picture fromPic, int startRow, int startCol)
{
  Pixel fromPixel = null;
  Pixel toPixel = null;
  Pixel[][] toPixels = this.getPixels2D();
  Pixel[][] fromPixels = fromPic.getPixels2D();
for (int fromRow = 0, toRow = startRow; fromRow < fromPixels.length && toRow < toPixels.length; fromRow++, toRow++)
{
  for (int fromCol = 0, toCol = startCol; fromCol < fromPixels[0].length && toCol < toPixels[0].length; fromCol++, toCol++)
   {
      fromPixel = fromPixels[fromRow][fromCol];
      toPixel = toPixels[toRow][toCol];
      toPixel.setColor(fromPixel.getColor());
   } 
  } 
}

public void createCollage()
  { 
    Picture flower1 = new Picture("flower1.jpg");
    Picture flower2 = new Picture("flower2.jpg");
    this.copy(flower1,0,0);
    this.copy(flower2,100,0);
    this.copy(flower1,200,0);
    Picture flowerNoBlue = new Picture(flower2);
    flowerNoBlue.zeroBlue();
    this.copy(flowerNoBlue,300,0);
    this.copy(flower1,400,0);
    this.copy(flower2,500,0);
    this.mirrorVertical();
    this.write("collage.jpg");
  }

Exercises
1. Create a second copy method that adds parameters to allow you to copy just part of the fromPic. You will need to add parameters that specify the start row, end row, start column, and end column to copy from. Write a class (static) test method in PictureTester to test this new method and call it in the main method.

2. Create a myCollage method that has at least three pictures (can be the same picture) copied three times with three different picture manipulations and at least one mirroring. Write a class (static) test method in PictureTester to test this new method and call it in the main method.