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

org.apache.pdfbox

pdfbox

2.0.16

org.apache.pdfbox

fontbox

2.0.16

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

com.github.jai-imageio

jai-imageio-core

1.4.0

com.github.jai-imageio

jai-imageio-jpeg2000

1.3.0

org.apache.pdfbox

jbig2-imageio

3.0.2

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

https://stackoverflow.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

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