(Java) Producing image by reading from a text-file filled with digits

Question

I'm a complete beginner in Java programming and I'm interested to learn more about its concepts.

Recently, I've been given an exercise which instructs me to display two versions of a picture. The picture to be displayed is provided in the form of a data file of 40,000 digits that are arranged in rows (although there is no marker between rows) and it starts from the top of the picture. So the first digit represents the top left corner of the picture and the last is the bottom right.

Basically, what the exercise wants me to construct a program that plots a dot in one of two colours for each digit. If the digit is in the range 0 to 3 the output should be one colour and for digits in the range 4 to 9 the dot should be in the other colour.

I understand I have to use arrays and also loops to perform this. I'm familiar with the fillEllipse, drawEllipse, drawRectangle and fillRectangle but this exercise is nothing I've attempted before.

Any hints on how to make this work? Your help would be greatly appreciated.

Answer 1

use Scanner to read the data like :

Scanner sc = new Scanner(new File("path_to_your_digits_file"));
int[][] digits= new int [200][200];
String line;
while(sc.hasNext()){//this means there is still a line to go
  line = sc.nextLine();
  //split the line and fill the array . or read char by char ,
  // i dont know how your file looks like, it's just some simple string manipulation here
  }
  int x;
  BufferedImage img = new BufferedImage(200,200,BufferedImage.TYPR_INT_RGB);
  for(int i=0;i<200;i++){
    for(int j=0;i<200;j++){
    if(digits[i][j]>0 && digits[i][j]<=3){
      x=//some color code;
     }else{
         x=//some other color code;
      } //not sure about this loop , again idk the structure of your file;
      img.setRGB(i,j,x);
     }
   }
      JLabel lbl = new JLabel();
      lbl.setSize(200,200);
      ImageIcon ico=new ImageIcon(img);
      lbl.setIcone(ico);
      lbl.setVisible(true);
      JFrame frame = new Jframe();
      frame.setSize(500,500);
      frame.add(lbl);
      frame.setVisible(true);

Answer 2

As a hint, rather than a complete solution, I would suggest looking into creating a java.awt.image.BufferedImage, and then set the colors of the individual pixels using the setRGB() method. You would then display this image using drawImage() on your Graphics object.

Answer 3

All what you need is how to read the digits from the file and put it into two dimension array

check this tutorial for how to read a file

Then you have to draw each pixel on a fram or a Panel

check this Java basic graphics tutorial

I hope this could help!