Question

我正在尝试用Java实现DDA算法来绘制一条线。 Line Rasterizer实现了一个接口。然后我在名为rasterizeLine的类中调用Canva函数。 LineRasterizes成功获得x和y点。没有错误被抛出，但是算法必须存在一些逻辑问题，因为没有绘制线。你能帮我找到合乎逻辑的错误吗？

接口

    package rasterops;

import rasterdata.RasterImage;

public interface LineRasterizer<PixelType> {
    RasterImage<PixelType> rasterizeLine(RasterImage<PixelType> img,
                  double x1, double y1, double x2, double y2,
                  PixelType value);
}

Line Rasterizer

package rasterops;

import rasterdata.RasterImage;

public class LineRasterizerDDA<PixelType> implements LineRasterizer <PixelType> {
    @Override
    public RasterImage<PixelType> rasterizeLine(RasterImage<PixelType> img, double x1, double y1, double x2, double y2, PixelType value) {


       double dy = y2-y1;
       double dx = x2-x1;

       double k = dy/dx;
       double y = y1;

        RasterImage<PixelType> result = img;
        for( double x = x1; x <= x2; x++ ){
            result = result.withPixel((int)x, (int)Math.round(y), value);
            y = y1 + k;
        }

        return result;



    }
}

Canva - 调用函数

panel.addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                previousX = e.getX();
                previousY = e.getY();
            }
        });
        panel.addMouseMotionListener(new MouseAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                final double startX = previousX / (panel.getWidth() - 1.0); //k zamysleni: proc 1.0 a ne 1?
                final double startY = 1 - previousY / (panel.getHeight() - 1.0);
                final double endX = e.getX() / (panel.getWidth() - 1.0);
                final double endY = 1 - e.getY() / (panel.getHeight() - 1.0);
                clear(); // zkuste zakomentovat
                rasterImage = liner.rasterizeLine(rasterImage,
                        startX, startY, endX, endY,
                        0xffff00);
                panel.repaint();
            }
        });

Answer 1

这一行：

y = y1 + k;

继续为y分配相同的值，因为y1和k并未发生变化。

Example output, drawing line between (0,0) and (10, 10)：

O..........
.OOOOOOOOOO
...........
...........
...........
...........
...........
...........
...........
...........
...........

你的意思是：

y = y + k;

或y += k;。

Example output, drawing line between (0,0) and (10, 10)：

O..........
.O.........
..O........
...O.......
....O......
.....O.....
......O....
.......O...
........O..
.........O.
..........O

实现DDA算法

1 个答案: