如何修复Java图形中的文本质量？ [英] How to fix text quality in Java graphics?

问题描述

代码：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;

import javax.swing.JFrame;

public class TextRectangle extends JFrame {

    private static final long serialVersionUID = 1L;

    public static void main(String[] a) {
        TextRectangle f = new TextRectangle();
        f.setSize(300, 300);
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(
            RenderingHints.KEY_TEXT_ANTIALIASING,
            RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        g2d.setRenderingHint(
            RenderingHints.KEY_RENDERING,
            RenderingHints.VALUE_RENDER_QUALITY);

        g2d.setColor(Color.WHITE);
        g2d.fillRect(0, 0, getWidth(), getHeight());

        g2d.setColor(Color.BLACK);
        g2d.setFont(new Font("Calibri", Font.BOLD, 18));
        g2d.drawString("Why does this text look so ugly?", 30, 150);
    }

}

结果：

正如您所看到的，字母间距不均匀。有时它是1像素，有时它是2或甚至3像素。另一个问题是'i'上面的点比底部宽。

As you can see the letter spacing is uneven. Sometimes it's 1px, sometimes it's 2 or even 3 pixels. Another issue is the dot above 'i' is wider than the bottom part.

在文本编辑器中编写的相同文本看起来要好得多。你知道如何解决这个问题吗？

The same text written in a text editor looks much better. Do you know how to fix this problem?

我的环境是Windows 8.1，Java 1.8。

My environment is Windows 8.1, Java 1.8.

推荐答案

图形上下文默认使用整数度量 - 意味着舍入应用于字形形状的位置向量。

The graphics context uses integer metrics by default - meaning that rounding is applied to the location vectors of the glyph shapes.

您可以切换到小数指标使用：

g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS,
    RenderingHints.VALUE_FRACTIONALMETRICS_ON);

如您所见，没有使用子像素抗锯齿（仅灰色抗锯齿像素）。您可以启用子像素抗锯齿以提高LCD屏幕的清晰度：

As you can see, no subpixel antialiasing was used (only gray antialias pixel). You can enable subpixel antialiasing for better legibility on LCD screens:

g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, 
    RenderingHints.VALUE_TEXT_ANTIALIAS_LCD_HRGB);

有4种模式：

• VALUE_TEXT_ANTIALIAS_LCD_HRGB ：水平定向RGB


• VALUE_TEXT_ANTIALIAS_LCD_HBGR ：水平定向BGR


• VALUE_TEXT_ANTIALIAS_LCD_VRGB ：垂直方向RGB


• VALUE_TEXT_ANTIALIAS_LCD_VBGR ：垂直方向BGR

• VALUE_TEXT_ANTIALIAS_LCD_HRGB: horizontally oriented RGB
• VALUE_TEXT_ANTIALIAS_LCD_HBGR: horizontally oriented BGR
• VALUE_TEXT_ANTIALIAS_LCD_VRGB: vertically oriented RGB
• VALUE_TEXT_ANTIALIAS_LCD_VBGR: vertically oriented BGR

我还没有找到查询当前显示和方向的适当值的位置。某些显示可以倾斜（横向/纵向）甚至旋转，需要在绘画时重新检测模式。

I haven't found out where to query the appropriate value of the current display and orientation. Some displays can be tilted (landscape/portrait) or even rotated, requiring to redetect the mode when painting.

编辑

我在 Filthy Rich Clients 书中找到了一些内容：显然，Java AWT工具包可以提供适当的渲染提示：

I found something in the Filthy Rich Clients book: apparently, the Java AWT Toolkit can provide appropriate rendering hints:

Map<?, ?> desktopHints = 
    (Map<?, ?>) Toolkit.getDefaultToolkit().getDesktopProperty("awt.font.desktophints");

Graphics2D g2d = (Graphics2D) g;
if (desktopHints != null) {
    g2d.setRenderingHints(desktopHints);
}
// no need to set more rendering hints

在我的系统上，这将使用小数度量和LCD HRGB抗锯齿呈现文本，与上面的代码相同。我系统上的提示是：

On my system, this renders the text with fractional metrics and LCD HRGB antialiasing, same as with the code above. The hints on my system are:

• 特定于文本的抗锯齿启用密钥： LCD HRGB抗锯齿文本模式


• 文字专用LCD对比度键： 120

• Text-specific antialiasing enable key: LCD HRGB antialiasing text mode
• Text-specific LCD contrast key: 120

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