/**
 * Program to draw a parabola into a PDF file.
 * 
 * Please note that the parabola is drawn sideways on the page, concave-right, so the y and x values have been interchanged in calculations. (i.e., x=y^2)
 * 
 * Adapted from tutorial found here: http://itextdocs.lowagie.com/examples/com/lowagie/examples/objects/images/RawData.java , written by Bruno Lowagie and Paulo Soares
 * 
 * Don't do anything important with this code. It's worth about as much as you paid for it (nothing).
 *
 * @author tqadmin@top-quark.com
 */


import java.io.FileOutputStream;
import java.io.IOException;

import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.Image;
import com.lowagie.text.pdf.PdfWriter;
import com.lowagie.text.PageSize;

/**
 * Using raw data to construct an Image object.
 */
public class ParabolaMaker {    
    /**
     * Parabola generation
     * @param args no arguments needed
     */
    public static void main(String[] args) {
        
        
        // step 1: creation of a document-object
        Document document = new Document(PageSize.LETTER,0,0,0,0);
        
        try {
            
            // step 2:
            // we create a writer that listens to the document
            // and directs a PDF-stream to a file
            PdfWriter.getInstance(document, new FileOutputStream("parabola.pdf"));
            
            // step 3: we open the document
            document.open();
            
            // step 4: we add content
            
			// ALTER THESE TO CHANGE THE DIMENSIONS OF THE PARABOLA
            double widthInches = 7;            // "width" of the mouth of the parabola
            double depthInches = 4.25;          // how deep the parabola is
			
			
			int PPI = 72;                       // points/inch
            int width = (int)(widthInches*PPI); // width, in points - y axis
            int depth = (int)(depthInches*PPI); // depth, in points - x axis
                    
            byte [] parabola = new byte[width*depth];   // Create a byte of grayscale data per point. A bit wasteful, but Java can only address bytes,
                                                        // and it'd be a waste of time to downgrade to bit or nibble resolution.
                                                        // As is, we're looking at ~485 kB for a full 8.5x11 page.
            
            double scaling = depth/Math.pow(width/2,2); // the k constant for the graph x = k y^2
            
            double focalDistance = 1/(scaling*4);   // parabolic math, where focal distance f = 1/4k
            
            int lineThickness = 1;  // horizontal thickness of the parabola trace
            
            // Building the image
            for (int y = 0; y < width; y++)
            {
                for (int x = 0; x < depth; x++)
                {
                    // define the parabola's value at this y-value
                    int ySquared = (int)Math.pow(y-width/2, 2);
                    
                    // fill "lineThickness" pixel(s) to each side of the parabola
                    if ( (x > scaling * ySquared - lineThickness) && (x < scaling * ySquared + lineThickness) )
                        parabola[y * depth + x] = (byte)0x00;   // 0x00 -> black trace
                    else
                        parabola[y * depth + x] = (byte)0xFF;   // 0xFF -> background is white
                        
                    // indicate the focal distance
                    if ( x == (int)focalDistance )
                        parabola[y * depth +x] = (byte)0x80;    // 0x80 -> line is gray
                    
                    // indicate line of symmetry
                    if (y == width/2)
                        parabola[y * depth +x] = (byte)0x80;    // 0x80 -> line is gray
                }
            }
            
            // parse the raw data into an image, with arguments of width being "depth", length being "width", 1 color channel, 8 bits per channel, from data "parabola"
            Image para = Image.getInstance(depth, width, 1, 8, parabola);
            
            // center the image on the page
            para.setAbsolutePosition( (document.getPageSize().width()-depth)/2, (document.getPageSize().height()-width)/2 );
            
            // add image to document
            document.add(para);
            
        }
        catch(DocumentException de) {
            System.err.println(de.getMessage());
        }
        catch(IOException ioe) {
            System.err.println(ioe.getMessage());
        }
        
        // step 5: we close the document
        document.close();
    }


}