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Java-如何绘制图形

发布于 2024-12-02 12:50:25 字数 160 浏览 3 评论 0原文

我试着环顾四周，但不明白如何用java绘制图形。让我举个例子。

假设我想创建一个自定义方法来填充三角形，它需要三个点作为参数。如果无法创建 Graphics 对象，如何使用 fillPolygon(int[] xPoints, int[] yPoints, int nPoints) 方法？

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苏辞 2024-12-09 12:50:25

您应该了解的第一件事（也许您已经知道）是 Graphics 是您写入到的位置，而不是您写入的位置。大多数时候它就是您的计算机屏幕，例如当您使用 Swing 时。

您还可以通过写入从 BufferedImage.getGraphics：

Image myImage = new BufferedImage(...);
Graphics graphImage = myImage.getGraphics();
graphImage.setColor(Color.BLUE);
graphImage.fillPolygon(...);  // set some blue pixels inside the BufferedImage

然后您可以将该图像转换为任何图像格式。

现在是一个愚蠢的例子，您不应该这样做（请参阅下面的真正的 Swing 过程）：
你可以在 Swing 组件中绘制图像

public class MyJPanel extends Panel {

   @Override
   public void paintComponent(Graphics g) { // g is your screen
       ... 
       g.drawImage(myImage,...);  // draw your image to the screen
       ...
   }
}

标准的 Swing 过程是直接写入屏幕：（

public class MyJPanel extends Panel {

   @Override
   public void paintComponent(Graphics g) { // g is your screen
       ... 
       g.fillPolygon(...); // directly writes your pixels to the screen buffer
       ...
   }
}

挑剔者的评论：直接写入屏幕缓冲区并不完全正确，因为 Swing 是双缓冲的。）

First thing you should understand (maybe you already know it) is that Graphics is where you write to, not where you write from. It is you computer screen most of the time, such as when you use Swing.

You can also draw directly to an empty image by writing in the Graphics obtained from BufferedImage.getGraphics:

Image myImage = new BufferedImage(...);
Graphics graphImage = myImage.getGraphics();
graphImage.setColor(Color.BLUE);
graphImage.fillPolygon(...);  // set some blue pixels inside the BufferedImage

You could then convert that image to any image format.

A stupid example now, which you should not do (see below for true Swing procedure):
you can draw your image in a Swing component

public class MyJPanel extends Panel {

   @Override
   public void paintComponent(Graphics g) { // g is your screen
       ... 
       g.drawImage(myImage,...);  // draw your image to the screen
       ...
   }
}

The standard Swing procedure is to write directly to the screen:

public class MyJPanel extends Panel {

   @Override
   public void paintComponent(Graphics g) { // g is your screen
       ... 
       g.fillPolygon(...); // directly writes your pixels to the screen buffer
       ...
   }
}

(Comment for the nitpickers: It is not quite true that you write directly to the screen buffer since Swing is double-buffered.)

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