Java Graphics2D正在关闭一个像素（舍入错误？） [英] Java Graphics2D is Drawing One Pixel Off (Rounding error?)

问题描述

我一直在尝试使用Graphics2D和PaintComponent在Java中创建程序。但是，Java没有正确地舍入一些值，导致一些点被渲染成与它应该给出不洁图像的位置不同的像素。你可以在下面的图片中看到我的意思。

这是我的代码。我可以改变什么来解决这个问题？谢谢！

  public void paintComponent（Graphics g）
 {
 super.paintComponent（g）; 
 
 g.setColor（Color.red）; 
 
 int orginX = getWidth（）/ 2; 
 int orginY = getHeight（）/ 2; 
 
 for（int i = 0; i< = 360; i + = 10）
 {
 double angle = Math.toRadians（i）; 
 double centerX = radius * Math.cos（angle）+ orginX; 
 double centerY = radius * Math.sin（angle）+ orginY; 
 int [] anglePointsX = {（int）（radius * Math.cos（angle + Math.toRadians（60））+ centerX），（int）（radius * Math.cos（angle-Math.toRadians（60） ））+ centerX），orginX}; 
 int [] anglePointsY = {（int）（radius * Math.sin（angle + Math.toRadians（60））+ centerY），（int）（radius * Math.sin（angle-Math.toRadians（60） ））+ centerY），orginY}; 
 g.drawPolygon（anglePointsX，anglePointsY，3）; 
} 
  

解决方案

尝试使用 i< 360 而不是 i< = 360 ，因为你已经在这个角度画了一条线（0 == 360）

尝试使用 Path2D 或 GeneralPath 而不是 drawPolygon 因为这会给你 float 和 double 精确度

查看

然后我使用<$ c $更改了绘图c> drawPolygon 使用 Shape API，特别是 Path2D

  @Override 
 protected void paintComponent（Graphics g）{
 super.paintComponent（g）; 
 
 Graphics2D g2d =（Graphics2D）g.create（）; 
 
 g2d.setColor（Color.red）; 
 g2d.setRenderingHint（RenderingHints.KEY_ALPHA_INTERPOLATION，RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY）; 
 g2d.setRenderingHint（RenderingHints.KEY_ANTIALIASING，RenderingHints.VALUE_ANTIALIAS_ON）; 
 g2d.setRenderingHint（RenderingHints.KEY_COLOR_RENDERING，RenderingHints.VALUE_COLOR_RENDER_QUALITY）; 
 g2d.setRenderingHint（RenderingHints.KEY_DITHERING，RenderingHints.VALUE_DITHER_ENABLE）; 
 g2d.setRenderingHint（RenderingHints.KEY_FRACTIONALMETRICS，RenderingHints.VALUE_FRACTIONALMETRICS_ON）; 
 g2d.setRenderingHint（RenderingHints.KEY_INTERPOLATION，RenderingHints.VALUE_INTERPOLATION_BILINEAR）; 
 g2d.setRenderingHint（RenderingHints.KEY_RENDERING，RenderingHints.VALUE_RENDER_QUALITY）; 
 g2d.setRenderingHint（RenderingHints.KEY_STROKE_CONTROL，RenderingHints.VALUE_STROKE_PURE）; 
 
 int orginX = getWidth（）/ 2; 
 int orginY = getHeight（）/ 2; 
 
 int dif =（int）（360 / 6d）; 
 for（int i = 0; i< 360; i + = dif）{
 double angle = Math.toRadians（i）; 
 double centerX = radius * Math.cos（angle）+ orginX; 
 double centerY = radius * Math.sin（angle）+ orginY; 
 
 Path2D path = new Path2D.Double（）; 
 path.moveTo（radius * Math.cos（angle + Math.toRadians（60））+ centerX，radius * Math.sin（angle + Math.toRadians（60））+ centerY）; 
 path.lineTo（（radius * Math.cos（angle  -  Math.toRadians（60））+ centerX），（radius * Math.sin（angle  -  Math.toRadians（60））+ centerY））; 
 path.lineTo（orginX，orginY）; 
 
 g2d.draw（路径）; 
} 
 g2d.dispose（）; 
} 
  

有和没有呈现提示

尽管如此，即使没有提示提示，问题也就消失了

I have been trying to make a program in Java using Graphics2D and PaintComponent. However, Java is not rounding some values correctly resulting in a few points being rendered a pixel different from where it supposed to be which gives an unclean image. You can see what I mean in the picture below.

Here is my code. What can I change to fix this? Thank you!

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

  g.setColor(Color.red);

  int orginX = getWidth()/2;
  int orginY = getHeight()/2;

  for(int i=0; i<=360; i+= 10)
  {
      double angle = Math.toRadians(i);
      double centerX = radius * Math.cos(angle) + orginX;
      double centerY = radius * Math.sin(angle) + orginY;
      int[] anglePointsX = {(int) (radius * Math.cos(angle+Math.toRadians(60)) + centerX), (int) (radius * Math.cos(angle-Math.toRadians(60)) + centerX), orginX};
      int[] anglePointsY = {(int) (radius * Math.sin(angle+Math.toRadians(60)) + centerY), (int) (radius * Math.sin(angle-Math.toRadians(60)) + centerY), orginY};
      g.drawPolygon(anglePointsX, anglePointsY, 3);
  }

解决方案

Try using i < 360 instead i<=360, as you've already drawen a line at this angle (0 == 360)

Try using a Path2D or GeneralPath rather then drawPolygon as this will give you float and double precision

Have a look at Drawing Arbitrary Shapes for more details

Updated...

So I changed i <= 360 to i < 360 and didn't see any immediate changes, however, then applied some rendering hints and it seemed to improve the problem.

I started by reducing the number of elements to 6 (this is where I started seeing an issue) with

int dif = (int) (360 / 6d);

for (int i = 0; i < 360; i += dif) {

Then I applied some rendering hints...

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    Graphics2D g2d = (Graphics2D) g.create();

    g2d.setColor(Color.red);
    g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
    g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
    g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
    g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

    int orginX = getWidth() / 2;
    int orginY = getHeight() / 2;

    int dif = (int) (360 / 6d);

    for (int i = 0; i < 360; i += dif) {
        double angle = Math.toRadians(i);
        double centerX = radius * Math.cos(angle) + orginX;
        double centerY = radius * Math.sin(angle) + orginY;
        int[] anglePointsX = {(int) (radius * Math.cos(angle + Math.toRadians(60)) + centerX), (int) (radius * Math.cos(angle - Math.toRadians(60)) + centerX), orginX};
        int[] anglePointsY = {(int) (radius * Math.sin(angle + Math.toRadians(60)) + centerY), (int) (radius * Math.sin(angle - Math.toRadians(60)) + centerY), orginY};
        g2d.drawPolygon(anglePointsX, anglePointsY, 3);
    }
    g2d.dispose();
}

Before and after comparison...

I then changed the drawing from using drawPolygon to use the Shape API, in particular a Path2D

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    Graphics2D g2d = (Graphics2D) g.create();

    g2d.setColor(Color.red);
    g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
    g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
    g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
    g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

    int orginX = getWidth() / 2;
    int orginY = getHeight() / 2;

    int dif = (int) (360 / 6d);
    for (int i = 0; i < 360; i += dif) {
        double angle = Math.toRadians(i);
        double centerX = radius * Math.cos(angle) + orginX;
        double centerY = radius * Math.sin(angle) + orginY;

        Path2D path = new Path2D.Double();
        path.moveTo(radius * Math.cos(angle + Math.toRadians(60)) + centerX, radius * Math.sin(angle + Math.toRadians(60)) + centerY);
        path.lineTo((radius * Math.cos(angle - Math.toRadians(60)) + centerX), (radius * Math.sin(angle - Math.toRadians(60)) + centerY));
        path.lineTo(orginX, orginY);

        g2d.draw(path);
    }
    g2d.dispose();
}

With and without rendering hints

As you can, even without rendering hints, the issue is gone

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