Question

Hi. I require your wonderful help with figuring out this challenging code.

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


public class ImageLab {

  /* 
   * This is the grayscale example. Use it for inspiration / help, but you dont
   * need to change it.
   *
   * Creates and returns a new BufferedImage of the same size as the input
   * image. The new image is the grayscale version of the input (red, green, and
   * blue components averaged together).
   */
  public static BufferedImage imageToGrayscale(BufferedImage input) {
    // store the image width and height in variables for later use
    int img_width = input.getWidth();
    int img_height = input.getHeight();

    // create a new BufferedImage with the same width and height as the input
    // image. TYPE_INT_RGB means we want to specify pixel values using their
    // red, green, and blue components.
    BufferedImage output_img = new BufferedImage(
        img_width, img_height, BufferedImage.TYPE_INT_RGB);

    // Loop over all pixels
    for (int x = 0; x < img_width; x++) {
      for (int y = 0; y < img_height; y++) {

        // Get the color of the input image as a java.awt.Color object
        Color color_at_pos = new Color(input.getRGB(x, y));

        // Call the getRed(), getGreen(), and getBlue() methods on the color
        // object to store the red, green, and blue values into separate integer
        // variables.
        int red = color_at_pos.getRed();
        int green = color_at_pos.getGreen();
        int blue = color_at_pos.getBlue();

        // to get the grayscale version, we just average the red, green, and
        // blue channels, then use that average as the red, green, and blue
        // values in the output image.
        int average = (red + green + blue) / 3;

        // You'll get an IllegalArgumentException if you try to specify red,
        // green, or blue values greater than 255 or less than 0. While it's
        // mathematically impossible to average three values in that range and
        // get a value outside the range, the calculations in the other tasks
        // will sometimes produce values outside the range. This code "clamps"
        // the value to the range 0 - 255
        if (average < 0) {
          average = 0;
        } else if (average > 255) {
          average = 255;
        }

        // make a new Color object, which has the average intensity ((r+g+b)/3)
        // for each of its channels.
        Color average_color = new Color(average, average, average);

        // in the output image, set the color at position (x,y) to our
        // calculated average color
        output_img.setRGB(x, y, average_color.getRGB());
      }
    }

    // return the output image.
    return output_img;
  }

  public static BufferedImage threshold(BufferedImage input, int level) {
    // Replace this method body with your code
    return null;
  }

  public static BufferedImage quantize(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }

  public static BufferedImage colorRotate(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }

  public static BufferedImage warhol(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }

  public static BufferedImage sharpen(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }

  public static BufferedImage boxBlur(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }

  public static BufferedImage simpleEdgeDetect(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }
 
  public static BufferedImage sobelEdgeDetect(BufferedImage input) {
    // Replace this method body with your code
    return null;
  }


  /*=============== You don't need to change anything below this line =======*/     

  public static BufferedImage readImage(String filename) {
    BufferedImage img = null;
    try {
      img = ImageIO.read(new File(filename));
    } catch (IOException e) {
      System.out.println("Error - couldn't load " + filename);
      return null;
    }

    return img;
  }

  public static void writeImage(BufferedImage img, String filename) {
                try {
      System.out.printf("Writing %s...\n", filename);
      File ImageFile = new File(filename);
                        ImageIO.write(img, "jpg", ImageFile);
                } catch (IOException e) {
      System.out.printf("Error writing %s\n", filename);
                        e.printStackTrace();
                }
  }

  public static void main(String[] args) {
    if (args.length == 0) {
      System.out.println("Usage: java ImageLab <filename>");
      System.exit(0);
    }

    BufferedImage img = readImage(args[0]);

    if(img == null) {
      System.out.println("Couldn't read image");
      System.exit(0);
    }

    System.out.println("Running imageToGrayscale()...");
    BufferedImage gray = imageToGrayscale(img);
    if (gray != null) {
      writeImage(gray, "grayscale.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running threshold()...");
    BufferedImage thresh = threshold(img, 128);
    if (thresh != null) {
      writeImage(thresh, "threshold.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running quantize()...");
    BufferedImage quant = quantize(img);
    if (quant != null) {
      writeImage(quant, "quant.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running colorRotate()...");
    BufferedImage rot = colorRotate(img);
    if (rot != null) {
      writeImage(rot, "colorrotate.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running warhol()...");
    BufferedImage war = warhol(img);
    if (war != null) {
      writeImage(war, "warhol.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running sharpen()...");
    BufferedImage sharp = sharpen(img);
    if (sharp != null) {
      writeImage(sharp, "sharpen.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running boxBlur()...");
    BufferedImage blur = boxBlur(img);
    if (blur != null) {
      writeImage(blur, "blur.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running simpleEdgeDetect()...");
    BufferedImage edge = simpleEdgeDetect(img);
    if (edge != null) {
      writeImage(edge, "edge.jpg");
    } else {
      System.out.println("Got null");
    }

    System.out.println("Running sobelEdgeDetect()...");
    BufferedImage sobel = sobelEdgeDetect(img);
    if (sobel != null) {
      writeImage(sobel, "sobel.jpg");
    } else {
      System.out.println("Got null");
    }

  }

}

Answer 1

The expression java.awt.Color refers to a file named Color.class.This is a class that has colors that we may use to change the apperance of the object int the interface which we are using.

In this,to change the apperance of area in browser while running program we use YELLOW color object.

Color begins with a capital letter that tells that it is a class file in java . Firstly note the path to the Color class.It is diffrent to the path of JApplet and JLabel classes.we all know that Classes in java are usually grouped together by functionality.

Many of the classes that control the apperance of GUI are contained in awt package. awt stands for "abstract windowing toolkit".

The classes in this package are contained in the version of java prior to java swing.That is the reason why the path is "java .awt.Color".