java 库将 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

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.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/main%20doc.pdf

 

 

参考文献

https://*.com/questions/42169154/pdfbox1-8-12-convert-pdf-to-white-page-image

https://*.com/questions/20424796/pdf-box-generating-blank-images-due-to-jbig2-images-in-it

https://blog.csdn.net/qq_15801963/article/details/80746830

https://my.oschina.net/u/2345654/blog/1058192