Explain this piece of java code?

AdultCaution · 08-08-2012 04:32PM #1

public static void main(String[] args) {
        
     String s = "D";
        if (s != null) {
            BufferedImage bi = new BufferedImage(80,20,BufferedImage.TYPE_INT_BGR);
            Graphics2D g2 = (Graphics2D)bi.getGraphics();
           g2.setFont(new Font("Serif", Font.BOLD, 12));
            g2.drawString(s, 0, 16);
            Raster ras = bi.getData();
           
            for (int row = 0; row < 20; row++) {
                String line = "";
                for (int col = 0; col < 80; col++) {
                    if (ras.getSample(col,row,1) > 128) {
                        line += "*";
                    } else {
                        line += " ";
                    }
                }
                System.out.println(line);
             
        
        
        
    }
    }
    }

I know it prints out the character in ascii, what I want to know (being a noob) is how do I tell what each field does and how does the program function in general? I have a general gist but I'm not quite there.

Say the 80 and the 20? Where do I look, what do I do to see that? What happens if I change it etc. I can see that it is width, height, type etc, but I dont know how much of an affect changing them has, and what values I should set. Is it measured in pixels? i can see it is coupled with the loop further down. I assume 12 is the size of the serif font? Then how does the 12 relate to the 80 and 20?

Similarly for g2.drawString(s, 0, 16);

Clearly s is d. What is 0 and what is 16? Just the location that I want to draw s? I just have trouble finding/understanding this information from documentation.

RedXIV · 08-08-2012 04:37PM

Can you execute the code?

If you can execute it and change the values a few times, I'm pretty sure you'd know what each of those numbers were for

srsly78 · 08-08-2012 05:25PM

The font is size 12, so the program only scans 20 rows - covers the char and some padding at top and bottom. Similarly for cols. It's set to 80 because the program was originally used with a longer string than just "D". These are just hardcoded values, a better way to do it would be to estimate the width from strlen somehow.

Yes the numbers refer to pixels.

The 0 and 16 refers to position for drawing (without this there would be no padding on the left). A simple google returns loads of api documentation.

The code is pretty poor and confusing tbh, lots of hackery and little consistency (see treatment of vertical vs horizontal padding).

lynchie · 09-08-2012 08:50AM

Code is quite simple. Draws the letter D on an image, gets the raw bitmap matrix and then scans through it. If the pixels have been affected by the drawing of the D it prints an * out for that line. The end result - ascii art!

Btw google Graphics2D and you will find the javadocs.

Genghiz Cohen · 09-08-2012 11:26AM

As above it looks like a basic ASCII art generator.
It draws a D to an image then scans the image pixel by pixel and checks to see if the RGB values pass a threshold (128) if they do write a '*' to file, else write a ' '

If you wanted to make it more advanced, you'd use a switch and a few other characters for the different amount of colour in each pixel. Then have a few different thresholds.

AdultCaution · 09-08-2012 01:54PM

Thanks guys that is great, very helpful. I cant execute the code at the moment so this helped a lot. I was just wondering the best way to do this, say take any user input and make it into ascii. But srsly78 says this code is bad, it certainly was confusing. I am quite crap at reading the docs as of yet.

srsly78 · 09-08-2012 02:04PM

You should really try to execute it, setting up java is trivial (and free). Staring at code is not a good way to learn, you have to tinker with it and run it.

Explain this piece of java code?

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