1. The difference between Graphics 2D and Graphics

tips: All in all, Graphics 2D is an enhanced version of Graphics, which enhances some advanced operations.

2. The specific use of setRenderingHint

tips: set up the processing methods of rendering image effects, such as anti-aliasing, color, difference and other effects processing algorithms. (I think anti-aliasing is useful now, but I will have different feelings in the future.) Here are two comparisons.

Unopened anti-aliasing

Open anti-aliasing

The following is the code implementation:

BufferedImage image = new BufferedImage(260, 80, BufferedImage.TYPE_INT_BGR);
//Getting Graphics 2D Objects
Graphics2D graphics = image.createGraphics();
//Open text anti-aliasing
graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
//Setting fonts
Font font = new Font("Algerian", Font.ITALIC, 40);
graphics.setFont(font);
//Write to the drawing board
graphics.drawString("This is test!", 10, 60);
graphics.dispose();

3. The Use of Stroke

tips: The equivalent of a brush head to define the characteristics of the lines drawn; different types of lines are represented by setting different parameters. More details can be seen in this article about the use of Basic Stroke, which is described in detail.

Here's a small example I wrote myself (specifying a background map and drawing a tree):

package com.msw.test;
 
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Polygon;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
 
import javax.imageio.ImageIO;
 
public class MyTest {
    public static void main(String[] args) throws IOException {
        BufferedImage image = new BufferedImage(400, 500, BufferedImage.TYPE_INT_BGR);
        BufferedImage image2 = ImageIO.read(new FileInputStream(new File("F:\\2.jpg")));
        // Getting Graphics 2D Objects
        Graphics2D graphics = image.createGraphics();
        graphics.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION,RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
        //Set image2 as background image
        graphics.drawImage(image2, 0, 0, 400, 500,null);
        // Setting Brushes
        Stroke stroke = new BasicStroke(5f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
        graphics.setStroke(stroke);
        // Set the color - Green
        graphics.setColor(Color.GREEN);
        //Painting trees
        graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        Polygon polygon = new Polygon();
        polygon.addPoint(200, 100);
        polygon.addPoint(180, 150);
        polygon.addPoint(220, 150);
        graphics.draw(polygon);
        polygon.reset();
        polygon.addPoint(200, 150);
        polygon.addPoint(160, 200);
        polygon.addPoint(240, 200);
        graphics.draw(polygon);
        polygon.reset();
        polygon.addPoint(200, 200);
        polygon.addPoint(140, 250);
        polygon.addPoint(260, 250);
        graphics.draw(polygon);
        polygon.reset();
        polygon.addPoint(180, 250);
        polygon.addPoint(180, 300);
        polygon.addPoint(220, 300);
        polygon.addPoint(220, 250);
        graphics.draw(polygon);
        graphics.dispose();
        File file = new File("F:\\1.jpg");
        file.createNewFile();
        FileOutputStream fos = new FileOutputStream(file);
        ImageIO.write(image, "jpg", fos);
        fos.close();
    }
}

Write on Graphics 2D pictures, calculate width and height, and position of fonts

As shown above, this is a string with Chinese and English characters. The width of Chinese characters is different from that of English characters. If I want to generate a wide and stiff picture, I need to calculate the width of each character and the appropriate height.

The class java.awt.FontMetrics gives a detailed introduction to the width and height of text.

 

Calculate the width of a string using fonts

 

public static int getWordWidth(Font font, String content) {
        FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font);
        int width = 0;
        for (int i = 0; i < content.length(); i++) {
            width += metrics.charWidth(content.charAt(i));
        }
        return width;
}

Calculate the maximum height of fonts used

   FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font);
   int height = metrics.getHeight();

Pictures are the most appropriate place to write text.

Ascent is the highest height from the baseline to the top. It can also be used as the most useful height for font drawing.

graphics.drawString(content, 0, metrics.getAscent());

Test code

import sun.font.FontDesignMetrics;
 
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.font.LineMetrics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
 
/**
 * Created by zengrenyuan on 18/5/11.
 */
public class ImageTest {
 
    public static void main(String[] args) throws IOException {
        Font font = new Font("Microsoft YaHei", Font.BOLD, 32);
        String content = "Hello Java!";
        FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font);
        int width = getWordWidth(font, content);//Calculate the width of the picture
        int height = metrics.getHeight();//Computational high
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics = bufferedImage.createGraphics();
        graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
        //Set back to white
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, bufferedImage.getWidth(), bufferedImage.getHeight());
        graphics.setFont(font);
        graphics.setColor(Color.BLACK);
        graphics.drawString(content, 0, metrics.getAscent());//Write words on pictures
        graphics.dispose();
        write(bufferedImage, "/data/test.png");
 
 
    }
 
    public static int getWordWidth(Font font, String content) {
        FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font);
        int width = 0;
        for (int i = 0; i < content.length(); i++) {
            width += metrics.charWidth(content.charAt(i));
        }
        return width;
    }
 
    public static void write(BufferedImage bufferedImage, String target) throws IOException {
        File file = new File(target);
        if (!file.getParentFile().exists()) {
            file.getParentFile().mkdirs();
        }
        try (OutputStream os = new FileOutputStream(target)) {
            ImageIO.write(bufferedImage, "PNG", os);
        }
    }
 
}