java的pdf轉jpg

1.依賴

<!--pdf轉jpg-->
        <dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>pdfbox</artifactId>
            <version>2.0.4</version>
        </dependency>

2.代碼

　　/**
     * pdf轉jpg
     * PDDocument.load(file)有多個重載方法
     */
    public List<BufferedImage> convertToImage(byte[] file) throws IOException {
        PDDocument document = PDDocument.load(file);
        PDFRenderer pdfRenderer = new PDFRenderer(document);
        List<BufferedImage> bufferedImageList = new ArrayList<>();
        for (int page = 0;page<document.getNumberOfPages();page++){
            BufferedImage img = pdfRenderer.renderImageWithDPI(page, 300, ImageType.RGB);
            bufferedImageList.add(img);
        }
        document.close();
        return bufferedImageList;
    }
    /**
     * 多頁合並
     */
    public BufferedImage concat(List<BufferedImage> images) {
        int heightTotal = 0;
        for(int j = 0; j < images.size(); j++) {
            heightTotal += images.get(j).getHeight();
        }
        int heightCurr = 0;
        BufferedImage concatImage = new BufferedImage(images.get(0).getWidth(), heightTotal, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = concatImage.createGraphics();
        for(int j = 0; j < images.size(); j++) {
            g2d.drawImage(images.get(j), 0, heightCurr, null);
            heightCurr += images.get(j).getHeight();
        }
        g2d.dispose();
        return concatImage;
    }