一.项目中导入pdfbox依赖

pom文件中添加：

		<!-- https://mvnrepository.com/artifact/org.apache.pdfbox/pdfbox -->
        <dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>pdfbox</artifactId>
            <version>2.0.25</version>
        </dependency>
        <dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>jbig2-imageio</artifactId>
            <version>3.0.2</version>
        </dependency>

二.编写代码

public static void imageToPdf(File imageFile, File outFile) throws IOException {
        BufferedImage image = ImageIO.read(imageFile);

        PDDocument outDocument = new PDDocument();

        PDImageXObject imageXObject = LosslessFactory.createFromImage(outDocument, image);
        PDPage pdPage = new PDPage(PDRectangle.A4);
        outDocument.addPage(pdPage);
        PDPageContentStream pageContentStream = new PDPageContentStream(outDocument, pdPage);
        float height = pdPage.getMediaBox().getHeight();//要将图片在pdf中绘制多高，这里宽度直接使用了pdfpage的宽度，即横向铺满，这里的height也是使用了pdfpage的高度。因此最终结果是铺满整个pdf页。
        float y = pdPage.getMediaBox().getHeight() - height;//这里比较奇葩的是这个坐标是以左下角为原点坐标的。
        pageContentStream.drawImage(imageXObject, 0, y, pdPage.getMediaBox().getWidth(), height);
        pageContentStream.close();

        if (!outFile.getParentFile().exists()) {
            outFile.getParentFile().mkdirs();
        }

        outDocument.save(outFile);
        outDocument.close();
    }