Graphics2D的旋转precision问题 [英] Graphics2D Rotation Precision Issues

问题描述

我画4层叠矩形，绕一个点在画布上，然后再次绘制相同的形状，但堆叠的矩形没有保持完全一致。

下面是截图：

正如你所看到的，第一不转动块是完美的，但下面的是对齐。为什么会出现这种情况，并哪能prevent呢？

---

SSCE

  //只需导入一切保持简短而亲切
进口java.awt中*。
导入的java.awt.geom *。
进口的javax.swing *。

@燮pressWarnings（串行）
公共类AlignmentIssue扩展JComponent的{
    @覆盖
    公共无效漆（图形G）{
        Graphics2D的G2D =（Graphics2D的）克;
        双角= Math.toRadians（30）;
        INT numRects =（INT）Math.floor（2.0 * Math.PI /角）;
        矩形RECT =新的Rectangle（0，100，20，25）;

        g2d.setRenderingHint（RenderingHints.KEY_ANTIALIASING，
                             RenderingHints.VALUE_ANTIALIAS_ON）;
        g2d.translate（的getWidth（）/ 2，的getHeight（）/ 2）;

        的for（int i = 0; I＆LT; numRects ++我）{
            的AffineTransform变换= g2d.getTransform（）;

            为（中间体n = 0时; N 3; ++ n）的{
                g2d.draw（RECT）;
                g2d.translate（0，rect.height）;
            }

            g2d.setTransform（变换）;
            g2d.rotate（角度）;
        }
    }

    公共静态无效的主要（字串[] args）{
        JFrame的框架=新的JFrame（对齐问题）;

        frame.add（新AlignmentIssue（））;
        frame.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
        frame.set preferredSize（新尺寸（800，600））;
        frame.pack（）;
        frame.setLocationRelativeTo（空）;
        frame.setVisible（真正的）;
    }
}
 

解决方案

您需要更多的precise行程控制：

  g2d.setRenderingHint（RenderingHints.KEY_STROKE_CONTROL，RenderingHints.VALUE_STROKE_PURE）;
 

默认可以让几何形状变化了一下，根据实现。纯试图保持亚像素精度。

I am drawing 4 stacked rectangles, rotating the canvas about a point and then drawing that same shape again but the stacked rectangles aren't remaining completely aligned.

Here's a screenshot:

As you can see, the first, unrotated block is perfect but the following ones are misaligned. Why is this happening and how can I prevent it?

---

SSCE

//Just import everything to keep it short and sweet
import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class AlignmentIssue extends JComponent {
    @Override
    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        double angle = Math.toRadians(30);
        int numRects = (int)Math.floor(2.0 * Math.PI / angle);
        Rectangle rect = new Rectangle(0, 100, 20, 25);

        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                             RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.translate(getWidth() / 2, getHeight() / 2);

        for(int i = 0; i < numRects; ++i) {
            AffineTransform transform = g2d.getTransform();

            for(int n = 0; n < 3; ++n) {
                g2d.draw(rect);
                g2d.translate(0, rect.height);
            }

            g2d.setTransform(transform);
            g2d.rotate(angle);
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Alignment Issue");

        frame.add(new AlignmentIssue());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setPreferredSize(new Dimension(800, 600));
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

解决方案

You need more precise stroke control:

g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

The default may let the geometry vary a bit, depending on the implementation. Pure tries to keep subpixel accuracy.

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