如何将iText Image转换为AWT BufferedImage（iText 2.1.7环境）

iText 2.1.7 没有提供直接转BufferedImage的公开API，核心实现分两步：优先提取原始图像字节直接解析，拿不到原始字节时先转AWT Image再重绘为BufferedImage，全程用公开API，不存在版本兼容问题。

完整转换代码 #

import com.lowagie.text.Image;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;

public class ItextImageConverter {
    public static BufferedImage toBufferedImage(Image itextImage) throws Exception {
        // 优先读取原始图像字节，无画质损失、性能最好
        byte[] rawImageData = itextImage.getRawData();
        if (rawImageData != null && rawImageData.length > 0) {
            try (ByteArrayInputStream inputStream = new ByteArrayInputStream(rawImageData)) {
                return ImageIO.read(inputStream);
            }
        }
        // 无原始字节的场景（如iText生成的条码、矢量转光栅图像），走重绘逻辑
        java.awt.Image awtImage = itextImage.getAwtImage();
        int width = awtImage.getWidth(null);
        int height = awtImage.getHeight(null);
        // 用ARGB色彩模式兼容透明通道
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        bufferedImage.getGraphics().drawImage(awtImage, 0, 0, null);
        return bufferedImage;
    }
}

压缩图片体积的参考实现 #

拿到BufferedImage后就可以自由控制压缩参数，比iText自带的压缩配置灵活度高很多，以下是JPG压缩示例：

import com.sun.image.codec.jpeg.JPEGImageWriteParam;
import javax.imageio.IIOImage;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.stream.ImageOutputStream;
import java.io.ByteArrayOutputStream;
import java.util.Iterator;

// 转换得到BufferedImage后，压缩为质量0.3的JPG
BufferedImage sourceImage = ItextImageConverter.toBufferedImage(originalItextImage);
ByteArrayOutputStream compressedBaos = new ByteArrayOutputStream();
Iterator<ImageWriter> jpgWriters = ImageIO.getImageWritersByFormatName("jpg");
ImageWriter jpgWriter = jpgWriters.next();
JPEGImageWriteParam writeParam = new JPEGImageWriteParam(null);
writeParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
// 压缩质量范围0-1，数值越小体积越小
writeParam.setCompressionQuality(0.3f);
try (ImageOutputStream ios = ImageIO.createImageOutputStream(compressedBaos)) {
    jpgWriter.setOutput(ios);
    jpgWriter.write(null, new IIOImage(sourceImage, null, null), writeParam);
}
// 用压缩后的字节重新生成iText Image对象即可写入PDF
Image compressedImage = Image.getInstance(compressedBaos.toByteArray());

注意事项 #

• 不要用反射读取iText内部私有字段实现转换，2.1.7不同小修订版的内部字段名有差异，容易出兼容问题
• 带透明通道的图片不要转JPG格式，会出现黑底异常，这类图可以转PNG后通过降低色深、调整采样率压缩体积

内容的提问来源于stack exchange，提问作者wytten