2025/06/05日日志 使用 Java 为图片添加各种样式的水印
使用 Java 为图片添加各种样式的水印
1. 水印的基本原理
无论是文本水印还是图像水印，其核心都是将水印内容绘制在目标图像上。Java 提供了强大的 Graphics2D 类，可以用来在图像上绘制各种图形和文本。以下是实现水印的关键点：
1.1 Graphics2D 简介
Graphics2D 是 java.awt.Graphics 类的子类，提供了更强大的图形处理能力，支持复杂的图形操作，如旋转、缩放、变换和抗锯齿等。在添加水印时，我们将使用 Graphics2D 对象来绘制水印。
1.2 AlphaComposite 控制透明度
在为图片添加水印时，通常需要控制水印的透明度，使其不会完全遮盖住原图。Java 中的 AlphaComposite 类允许我们通过设置透明度来混合图像和水印。
1.3 水印的位置与布局
水印的位置是指在目标图像上的具体绘制位置。水印可以放置在图像的任意位置，如左上角、右下角或中心等。我们可以通过控制 Graphics2D 对象的绘制坐标来实现水印的位置调整。
2. 实现文本水印
文本水印是最简单的一种水印形式，通常用于在图像上添加文字信息，如作者名、版权声明或其他标识。
2.1 添加简单的文本水印
以下是一个简单的代码示例，展示了如何在图像的右下角添加一段文本作为水印：
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
public class TextWatermark {
public static void addTextWatermark(String text, File sourceImageFile, File destImageFile) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
g2d.setComposite(alphaChannel);
g2d.setColor(Color.GRAY);
g2d.setFont(new Font("Arial", Font.BOLD, 64));
int x = sourceImage.getWidth() - 100;
int y = sourceImage.getHeight() - 50;
g2d.drawString(text, x, y);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Text watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static void main(String[] args) {
File sourceImageFile = new File("src/main/resources/source-image.jpg");
File destImageFile = new File("src/main/resources/watermarked-image.jpg");
String watermarkText = "© 2024 MyCompany";
addTextWatermark(watermarkText, sourceImageFile, destImageFile);
}
}
2.2 自定义水印位置
我们可以通过传入 x 和 y 参数，灵活地控制水印文本的位置：
public static void addTextWatermark(String text, File sourceImageFile, File destImageFile, int x, int y) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
g2d.setComposite(alphaChannel);
g2d.setColor(Color.GRAY);
g2d.setFont(new Font("Arial", Font.BOLD, 64));
g2d.drawString(text, x, y);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Text watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
2.3 自定义水印样式
我们还可以通过调整字体、颜色和透明度等参数来自定义水印的样式：
public static void addStyledTextWatermark(String text, File sourceImageFile, File destImageFile) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.3f);
g2d.setComposite(alphaChannel);
g2d.setColor(Color.BLUE);
g2d.setFont(new Font("Courier New", Font.ITALIC, 80));
int x = 20;
int y = 100;
g2d.drawString(text, x, y);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Styled text watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
3. 实现图像水印
图像水印通常用于添加公司 Logo 或品牌标识。实现图像水印的步骤与文本水印类似，只是将 drawString 替换为 drawImage。
3.1 添加简单的图像水印
以下是一个将 Logo 作为水印添加到目标图像的示例：
public static void addImageWatermark(File watermarkImageFile, File sourceImageFile, File destImageFile) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
BufferedImage watermarkImage = ImageIO.read(watermarkImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
g2d.setComposite(alphaChannel);
int x = sourceImage.getWidth() - watermarkImage.getWidth() - 10;
int y = sourceImage.getHeight() - watermarkImage.getHeight() - 10;
g2d.drawImage(watermarkImage, x, y, null);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Image watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
3.2 自定义图像水印大小
有时，水印图像的尺寸可能与目标图像不匹配。我们可以对水印图像进行缩放，使其适应目标图像的大小：
public static void addScaledImageWatermark(File watermarkImageFile, File sourceImageFile, File destImageFile) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
BufferedImage watermarkImage = ImageIO.read(watermarkImageFile);
int scaledWidth = sourceImage.getWidth() / 5;
int scaledHeight = watermarkImage.getHeight() * scaledWidth / watermarkImage.getWidth();
Image scaledWatermark = watermarkImage.getScaledInstance(scaledWidth, scaledHeight, Image.SCALE_SMOOTH);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
g2d.setComposite(alphaChannel);
int x = sourceImage.getWidth() - scaledWidth - 10;
int y = sourceImage.getHeight() - scaledHeight - 10;
g2d.drawImage(scaledWatermark, x, y, null);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Scaled image watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
4. 实现平铺水印
平铺水印是一种将水印重复覆盖整个图像的技术，以增加图像的保护难度。平铺水印可以是文本，也可以是图像。
4.1 平铺文本水印
以下是一个平铺文本水印的实现：
public static void addTiledTextWatermark(String text, File sourceImageFile, File destImageFile) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.2f);
g2d.setComposite(alphaChannel);
g2d.setColor(Color.LIGHT_GRAY);
g2d.setFont(new Font("Arial", Font.BOLD, 40));
FontMetrics fontMetrics = g2d.getFontMetrics();
int textWidth = fontMetrics.stringWidth(text);
int textHeight = fontMetrics.getHeight();
for (int x = 0; x < sourceImage.getWidth(); x += textWidth + 20) {
for (int y = textHeight; y < sourceImage.getHeight(); y += textHeight + 20) {
g2d.drawString(text, x, y);
}
}
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Tiled text watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
4.2 平铺图像水印
以下是一个平铺图像水印的实现：
public static void addTiledImageWatermark(File watermarkImageFile, File sourceImageFile, File destImageFile) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
BufferedImage watermarkImage = ImageIO.read(watermarkImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.3f);
g2d.setComposite(alphaChannel);
for (int x = 0; x < sourceImage.getWidth(); x += watermarkImage.getWidth() + 20) {
for (int y = 0; y < sourceImage.getHeight(); y += watermarkImage.getHeight() + 20) {
g2d.drawImage(watermarkImage, x, y, null);
}
}
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Tiled image watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
5. 综合示例：创建一个水印工具类
为了便于重复使用，我们可以将上述不同类型的水印方法封装到一个工具类中。这样可以更方便地在不同项目中应用水印功能：
public class WatermarkUtils {
public static void addTextWatermark(String text, File sourceImageFile, File destImageFile, float opacity, Color color, Font font, int x, int y) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity);
g2d.setComposite(alphaChannel);
g2d.setColor(color);
g2d.setFont(font);
g2d.drawString(text, x, y);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Text watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static void addImageWatermark(File watermarkImageFile, File sourceImageFile, File destImageFile, float opacity, int x, int y) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
BufferedImage watermarkImage = ImageIO.read(watermarkImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity);
g2d.setComposite(alphaChannel);
g2d.drawImage(watermarkImage, x, y, null);
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Image watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static void addTiledTextWatermark(String text, File sourceImageFile, File destImageFile, float opacity, Color color, Font font, int xStep, int yStep) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity);
g2d.setComposite(alphaChannel);
g2d.setColor(color);
g2d.setFont(font);
FontMetrics fontMetrics = g2d.getFontMetrics();
int textWidth = fontMetrics.stringWidth(text);
int textHeight = fontMetrics.getHeight();
for (int x = 0; x < sourceImage.getWidth(); x += textWidth + xStep) {
for (int y = textHeight; y < sourceImage.getHeight(); y += textHeight + yStep) {
g2d.drawString(text, x, y);
}
}
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Tiled text watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static void addTiledImageWatermark(File watermarkImageFile, File sourceImageFile, File destImageFile, float opacity, int xStep, int yStep) {
try {
BufferedImage sourceImage = ImageIO.read(sourceImageFile);
BufferedImage watermarkImage = ImageIO.read(watermarkImageFile);
Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();
AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity);
g2d.setComposite(alphaChannel);
for (int x = 0; x < sourceImage.getWidth(); x += watermarkImage.getWidth() + xStep) {
for (int y = 0; y < sourceImage.getHeight(); y += watermarkImage.getHeight() + yStep) {
g2d.drawImage(watermarkImage, x, y, null);
}
}
ImageIO.write(sourceImage, "png", destImageFile);
g2d.dispose();
System.out.println("Tiled image watermark added successfully.");
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
通过以上示例代码，可以轻松实现 Java 图像处理中的水印功能。
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