java 图片拉伸 java提高图片清晰度

java 库 pdfbox 将 pdf 文件转换成高清图片方法

近期需要将 pdf 文件转成高清图片，使用库是 pdfbox、fontbox。可以使用 renderImageWithDPI 方法指定转换的清晰度，当然清晰度越高，转换需要的时间越长，转换出来的图片越大，越清晰。

说明：由于 adobo 软件越来越强大，支持的格式越来越多，这造成了 java 软件有些不能转换。所以对于新的格式可能会有转换问题。

1 引入依赖

<dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>pdfbox</artifactId>
            <version>2.0.16</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.pdfbox/fontbox -->
        <dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>fontbox</artifactId>
            <version>2.0.16</version>
        </dependency>

 

2 代码如下

public static void convertPdf2Image(String pdfPath, String imageDirPath) {
        log.info("start convert pdf file:[{}] to image path:[{}]", pdfPath, imageDirPath);
        if (!new File(pdfPath).exists()) {
            log.info("pdfFilename:[{}] not exist", pdfPath);
            return;
        }
        if (!new File(imageDirPath).exists()) {
            log.info("imageDir:[{}] not exist", imageDirPath);
            return;
        }
        byte[] pdfContent = FileUtil.getFileContentByte(pdfPath);
        String filename = FileUtil.getFilename(pdfPath);
        float dpi = 200;
        convertPdf2Image(pdfContent, filename, imageDirPath, dpi);
        log.info("convert pdf file:[{}] to image success", filename);
    }

private static void convertPdf2Image(byte[] pdfContent, String pdfFilename, String imageDirPath, float dpi) {
        log.info("convert pdfFilename:[{}] to imageDir:[{}] with dpi:[{}]", pdfFilename, imageDirPath, dpi);
        if (ArrayUtils.isEmpty(pdfContent)) {
            return;
        }
        // 为了保证显示清除，至少 90
        if (dpi < 90) {
            dpi = 90;
        }
        String baseSir = imageDirPath;
        if (baseSir.endsWith("/") || baseSir.endsWith("\\")) {
            baseSir += pdfFilename + "_";
        } else {
            baseSir += File.separator + pdfFilename + "_";
        }
        PDDocument document = null;
        BufferedOutputStream outputStream = null;
        try {
            document = PDDocument.load(pdfContent);
            int pageCount = document.getNumberOfPages();
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            String imgPath;
            for (int i = 0; i < pageCount; i++) {
                imgPath = baseSir + i + ".png";
                outputStream = new BufferedOutputStream(new FileOutputStream(imgPath));
                BufferedImage image = pdfRenderer.renderImageWithDPI(i, dpi, ImageType.RGB);
                ImageIO.write(image, "png", outputStream);
                outputStream.close();
                log.info("convert to png, total[{}], now[{}], ori:[{}], des[{}]", pageCount, i + 1, pdfFilename, imgPath);
            }
        } catch (IOException e) {
            log.error("convert pdf to image error, pdfFilename:" + pdfFilename, e);
        } finally {
            IOUtil.closeSilently(outputStream);
            IOUtil.closeSilently(document);
        }
    }

// IOUtil.closeSilently 代码
public static void closeSilently(Closeable io) {
        if (io != null) {
            try {
                io.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

在实际使用中遇到问题

1）ERROR o.a.p.contentstream.PDFStreamEngine 911 - Cannot read JBIG2 image: jbig2-imageio is not installed

2）Cannot read JPEG2000 image: Java Advanced Imaging (JAI) Image I/O Tools are not installed

3) java.lang.IllegalArgumentException: Numbers of source Raster bands and source color space components do not match at java.awt.image.ColorConvertOp.filter

以上两个问题需要使用 JAI 插件和 jbig2 插件支持，通过引入 jai-imageio-core、jai-imageio-jpeg2000、jbig2-imageio

<dependency>
<groupId>com.twelvemonkeys.imageio</groupId>
<artifactId>imageio-jpeg</artifactId>
<version>3.4.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.github.jai-imageio/jai-imageio-core -->
<dependency>
<groupId>com.github.jai-imageio</groupId>
<artifactId>jai-imageio-core</artifactId>
<version>1.4.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.github.jai-imageio/jai-imageio-jpeg2000 -->
<dependency>
<groupId>com.github.jai-imageio</groupId>
<artifactId>jai-imageio-jpeg2000</artifactId>
<version>1.3.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.pdfbox/jbig2-imageio -->
<dependency>
<groupId>org.apache.pdfbox</groupId>
<artifactId>jbig2-imageio</artifactId>
<version>3.0.2</version>
</dependency>

参考问题文件

https://github.com/crazyCodeLove/studentservice/blob/master/sys/src/main/resources/pdffile/000208-p1.pdf

https://github.com/crazyCodeLove/studentservice/blob/master/sys/src/main/resources/pdffile/001659-p14.pdf

https://github.com/crazyCodeLove/studentservice/blob/master/sys/src/main/resources/pdffile/573636.pdf