Usecka trivilanim algortimem

package cz.uhk.vanclma2.tvary;

import java.awt.Color;
import java.awt.Point;

import cz.uhk.vanclma2.gui.DrawImage;

/**
 *
 * @author Martin Vancl
 *
 */

public class UseckaTrivial implements TvaryIface {
    private int x1;
    private int y1;
    private int x2;
    private int y2;
    private Color barva;

    /**
     * Nakresli usecku trivialnim algoritmem. Trida UseckaTrivial obsahuje metody pro ScanLine
     * vyplnovaci algoritmus - je nutne ji pouzit pro ScanLine.
     * @param start
     *              Pocatecni bod usecky
     * @param cil
     *              Koncovy bod usecky
     * @param barva
     *              Barva usecky
     */
    public UseckaTrivial(Point start, Point cil, Color barva) {
        this.x1 = start.x;
        this.y1 = start.y;
        this.x2 = cil.x;
        this.y2 = cil.y;
        this.barva = barva;
    }


    // pro scan line ###########################################

    public UseckaTrivial(UseckaTrivial usecka) {
        this.x1 = usecka.x1;
        this.x2 = usecka.x2;
        this.y1 = usecka.y1;
        this.y2 = usecka.y2;
    }

    /**
     * Otoci smer usecky
     */
    public void prohodKoncoveBody() {
        if (y2 < y1) {
            int p;

            p = x1;
            x1 = x2;
            x2 = p;

            p = y1;
            y1 = y2;
            y2 = p;
        }
    }

    /**
     * Najde prusecik 2 usecek
     */
    public int zjistiPrusecik(int y) {
        float dy = y1 - y2;
        float dx = x1 - x2;
        float k = dx / dy;
        float q = k * (y - y1) + x1;
        return (int) q;
    }

    /**
     * U vodorovnych usecek se nepocitaji pruseciky
     * @return true/false podle toho, jestli je vodorovna
     */
    public boolean jeVodorovna() {
        return (y2 == y1);
    }

    public boolean jePrusecik(int y) {
        return ((y1 < y) && (y <= y2));
    }

    public int getX1() {
        return x1;
    }

    public int getY1() {
        return y1;
    }

    public int getX2() {
        return x2;
    }

    public int getY2() {
        return y2;
    }

    // pro scan line ###########################################

    public void kresli() {
        // http://cs.wikipedia.org/wiki/P%C5%99%C3%ADmka#Sm.C4.9Brnicov.C3.A1_rovnice_p.C5.99.C3.ADmky
        if (Math.abs(x2 - x1) > Math.abs(y2 - y1)) { // k<1 - funkce klesajici
            if (x1 > x2) {  // vymena koncovych bodu
                int pomocna1;
                pomocna1 = x2;
                x2 = x1;
                x1 = pomocna1;

                int pomocna2;
                pomocna2 = y2;
                y2 = y1;
                y1 = pomocna2;
        }
            float k = (float)(y1 - y2) / (x1 - x2); // k = smernice primky, vyjadruje sklon
            float q = y2 - k * x2; // posunuti na ose y

            for (int x = x1; x <= x2; x++) {
                int y = (int)(k * x + q);
                DrawImage.kresliPixel(x, y, barva);
            }
        } else { // k>0 - funkce rostouci
            if (y1 > y2) {  // vymena koncovych bodu
                int pomocna1;
                pomocna1 = x2;
                x2 = x1;
                x1 = pomocna1;

                int pomocna2;
                pomocna2 = y2;
                y2 = y1;
                y1 = pomocna2;
            }
            float k = (float)(x1 - x2) / (y1 - y2);
            float q = x2 - k * y2;

            for (int y = y1; y <= y2; y++) {
                int x = (int)(k * y + q);
                DrawImage.kresliPixel(x, y, barva);
            }
        }
    }
}