teaching machines

CS 145 Lecture 22 – Loops IV

October 22, 2014 by Chris Johnson. Filed under cs145, fall 2014, lectures.

Agenda

• what ?s
• program this
• inverting a BufferedImage
• blackboxes

TODO

• No Weekly Outside Problem this week.
• Mercy Fortnight expires before Friday.

Blackboxes

• Blackbox 7
• Blackbox 6
• Blackbox 8

Program This

Code

GetThird.java

package lecture1022;

import java.util.Scanner;

public class GetThird {
  public static String getThird(String csv) {
    Scanner in = new Scanner(csv);
    int target = 3;
    String field = null;
    for (int i = 0; i < target; ++i) {
      if (in.hasNext()) {
        field = in.next();
      } else {
        return null;
      }
    }
    return field;
  }
}

Image.java

package lecture1022;

import java.util.Random;

public class Image {
  public static void main(String[] args) {
    int width = 512;
    int height = 256;

    System.out.println("P2");
    System.out.println(width + " " + height);
    System.out.println(255);

    makeHorizontalGradient(width, height);
  }

  public static void makeHorizontalGradient(int width,
                                            int height) {
    double jump = 255.0 / width;

    for (int r = 0; r < height; ++r) {
      double brightness = 0;
      for (int c = 0; c < width; ++c) {
        if (r < height / 2) {
          brightness += jump;
          System.out.println((int) brightness);
        } else {
          System.out.println((int) (255.0 * c / (double) width));
        }
      }
    }
  }

  public static void makeGradient(int width,
                                  int height) {
    for (int r = 0; r < height; ++r) {
      for (int c = 0; c < width; ++c) {
        System.out.println((int) (c / (double) width * 255.0));
      }
    }
  }

  public static void makeXor(int width,
                             int height) {
    for (int r = 0; r < height; ++r) {
      for (int c = 0; c < width; ++c) {
        System.out.println((c ^ r) % 256);
      }
    }
  }

  public static void makeChecks(int width,
                                int height) {
    for (int r = 0; r < height; ++r) {
      for (int c = 0; c < width; ++c) {
        if (r / 10 % 2 != c / 10 % 2) {
          System.out.println(255);
        } else {
          System.out.println(0);
        }
      }
    }
  }

  public static void makeStatic(int width,
                                int height) {
    Random g = new Random();

    for (int r = 0; r < height; ++r) {
      for (int c = 0; c < width; ++c) {
        System.out.println(g.nextInt(256));
      }
    }
  }

  public static void makeStripes(int width,
                                 int height) {
    for (int r = 0; r < height; ++r) {
      for (int c = 0; c < width; ++c) {
        if (c % 10 <= 3) {
          System.out.println(0);
        } else {
          System.out.println(255);
        }
      }
    }
  }

  public static void makeDiagonals(int width,
                                   int height) {
    for (int r = 0; r < height; ++r) {
      for (int c = 0; c < width; ++c) {
        // if (r % 10 == c % 10) {
        if ((r + width - c) % 20 < 10) {
          System.out.println(0);
        } else {
          System.out.println(255);
        }
      }
    }
  }

  public static void makePacman(int width,
                                int height) {
    int rCenter = height / 2;
    int cCenter = width / 2;

    for (int r = 0; r < height; ++r) {
      int diffR = r - rCenter;
      for (int c = 0; c < width; ++c) {
        int diffC = c - cCenter;
        double distance = Math.hypot(diffR, diffC);
        if (distance < 14) {
          System.out.println(0);
        } else {
          System.out.println(255);
        }
      }
    }
  }
}

Inverter.java

package lecture1022;

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class Inverter {
  public static void main(String[] args) throws IOException {
    BufferedImage image = ImageIO.read(new File("/Users/johnch/Desktop/rainbow.png"));
    BufferedImage inverted = invert(image);
    ImageIO.write(inverted, "png", new File("/Users/johnch/Desktop/inverted.png"));
  }

  public static BufferedImage invert(BufferedImage src) {
    BufferedImage dst = new BufferedImage(src.getWidth(),
                                          src.getHeight(),
                                          src.getType());
    // traverse image
    // for each pixel
    //   find its complement
    for (int r = 0; r < src.getHeight(); ++r) {
      for (int c = 0; c < src.getWidth(); ++c) {
        int packedColor = src.getRGB(c, r);
        Color color = new Color(packedColor);
        int redComplement = 255 - color.getRed();
        int greenComplement = 255 - color.getGreen();
        int blueComplement = 255 - color.getBlue();
        Color complementColor = new Color(redComplement, greenComplement, blueComplement);
        int packedComplementColor = complementColor.getRGB();
        dst.setRGB(c, r, packedComplementColor);
      }
    }
    
    return dst;
  }
}

Haiku