java - java中如何在对角线上画一个圆？

Question

我有一条对角线，从屏幕的左下部分开始到屏幕的右上部分。现在我想在从左下部分开始到右上部分的距离为100米的线上画一个圆，这就是我的问题。您能给我一些关于这件事的想法吗？

任何帮助将不胜感激...

代码如下:

public void paint(Graphics g)
{
    super.paint(g);

    Graphics2D g2d = (Graphics2D) g;
    g2d.setBackground(Color.white);

    int x0_pixel = 0;
    int y0_pixel = 0;

    int x1_pixel = getWidth();
    int y1_pixel = getHeight();

    int x0_world = 0;
    int y0_world = 0;

    double x1_world = 2000; // meters
    double y1_world = 1125; // meters

    double x_ratio = (double) x1_pixel / x1_world;
    double y_ratio = (double) y1_pixel / y1_world;

    int xFrom = 0;
    int yFrom = 0;

    double xTo = x1_world;
    double yTo = y1_world;

    int FromX_pixel = convertToPixelX(xFrom, x_ratio);
    int FromY_pixel = convertToPixelY(y1_pixel, yFrom, y_ratio);

    int ToX_pixel = convertToPixelX((int) xTo, x_ratio);
    int ToY_pixel = convertToPixelY(y1_pixel, (int) yTo, y_ratio);

    g2d.setColor(Color.RED);
    g2d.drawLine(FromX_pixel, FromY_pixel, ToX_pixel, ToY_pixel);

    double theta = Math.atan(yTo / xTo);

    double len = (int) Math.sqrt(xTo * xTo + yTo * yTo);

    int interval = 100;

    for (int distance = xFrom; distance < len; distance += interval)
    {
        double distance_x = (int) Math.cos(theta * distance);
        double distance_y = (int) Math.sin(theta * distance);

        int x_circle_pixel = convertToPixelCircleX(FromX_pixel, distance_x);
        int y_circle_pixel = convertToPixelCircleY(y1_pixel, distance_y, y_ratio);

        g2d.drawOval(x_circle_pixel, y_circle_pixel, 10, 10);
    }

    Toolkit.getDefaultToolkit().sync();
    g2d.dispose();

 }

 private static int convertToPixelY(int y_offset, int y_world, double y_ratio)
 {
     return (int) (y_offset - (y_world * y_ratio));
 }

 private static int convertToPixelX(int x_world, double ratio)
 {
     return (int) (x_world * ratio);
 }

private static int convertToPixelCircleY(int y_offset, double distance, double y_ratio)
{
     return (int) (y_offset - (distance * y_ratio));
}

private static int convertToPixelCircleX(int x_world, double distance_x)
{
     return (int) (x_world * distance_x);
} 

Answer 1

看看你的 FOR 部分，我相信这就是错误所在。

final double cosTheta = Math.cos(theta);
final double sinTheta = Math.sin(theta);

for (int distance = xFrom; distance < len; distance += interval) {

    double distance_x = distance * cosTheta;
    double distance_y = distance * sinTheta;

    //int x_circle_pixel = convertToPixelCircleX(FromX_pixel, distance_x);
    //int y_circle_pixel = convertToPixelCircleY(y1_pixel, distance_y, y_ratio);
    int x_circle_pixel = convertToPixelX((int) distance_x, x_ratio);
    int y_circle_pixel = convertToPixelY(y1_pixel, (int) distance_y, y_ratio);

    g2d.drawOval(x_circle_pixel, y_circle_pixel, 10, 10);
}