Java图像处理：库与代码示例 | PythonLib

Java图像处理：库与实战示例

Java提供了强大的内置工具用于处理位图图像。本文将介绍标准库javax.imageio、包java.awt.image以及流行的第三方库Thumbnailator。您将学习如何读取、保存、缩放、应用滤镜以及转换图像格式。

1. 基础：javax.imageio包与BufferedImage

内存中表示图像的关键类是BufferedImage。它允许您获取和修改像素，处理不同的色彩模型（RGB、ARGB）和数据类型。

从文件读取图像

import javax.imageio.ImageIO;import java.awt.image.BufferedImage;import java.io.File;import java.io.IOException;

public class ImageReadExample {    public static void main(String[] args) {        try {            File inputFile = new File("input.jpg");            BufferedImage image = ImageIO.read(inputFile);            System.out.println("宽度: " + image.getWidth());            System.out.println("高度: " + image.getHeight());            System.out.println("类型: " + image.getType());        } catch (IOException e) {            e.printStackTrace();        }    }}

将图像写入文件

File outputFile = new File("output.png");ImageIO.write(image, "png", outputFile); // 格式根据扩展名确定

支持的格式：JPEG、PNG、BMP、WBMP、GIF（仅读取）。完整列表可通过ImageIO.getReaderFormatNames()获取。

2. 使用Java 2D进行缩放和变换

java.awt.Graphics2D包允许您进行高质量的缩放、旋转、镜像和图像叠加。

保持比例的缩放

import java.awt.Graphics2D;import java.awt.RenderingHints;import java.awt.image.BufferedImage;

public class ImageResizer {    public static BufferedImage resize(BufferedImage original, int targetWidth, int targetHeight) {        BufferedImage resized = new BufferedImage(targetWidth, targetHeight, original.getType());        Graphics2D g2d = resized.createGraphics();                // 启用抗锯齿以获得更好的质量        g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION,                RenderingHints.VALUE_INTERPOLATION_BILINEAR);        g2d.setRenderingHint(RenderingHints.KEY_RENDERING,                RenderingHints.VALUE_RENDER_QUALITY);        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,                RenderingHints.VALUE_ANTIALIAS_ON);                g2d.drawImage(original, 0, 0, targetWidth, targetHeight, null);        g2d.dispose();        return resized;    }}

将图像旋转90度

public static BufferedImage rotate(BufferedImage image, double angleDegrees) {    double radians = Math.toRadians(angleDegrees);    int w = image.getWidth();    int h = image.getHeight();        // 旋转后的新尺寸    int newW = (int) Math.abs(w * Math.cos(radians)) + (int) Math.abs(h * Math.sin(radians));    int newH = (int) Math.abs(h * Math.cos(radians)) + (int) Math.abs(w * Math.sin(radians));        BufferedImage rotated = new BufferedImage(newW, newH, BufferedImage.TYPE_INT_ARGB);    Graphics2D g2d = rotated.createGraphics();    g2d.translate((newW - w) / 2.0, (newH - h) / 2.0);    g2d.rotate(radians, w / 2.0, h / 2.0);    g2d.drawImage(image, 0, 0, null);    g2d.dispose();    return rotated;}