Question

我试图将图像作为pdf文件的新页面，jpeg图像的大小太大，虽然它被添加得很好，但是在将pdf转换为Tiff时面临问题，它抛出了内存异常，是否有办法压缩这些jpeg文件

以下代码将图片转换为pdf

PDImageXObject image = PDImageXObject.createFromFile(imagePath, doc);           
            PDPage page = new PDPage(new PDRectangle(image.getWidth(), image.getHeight()));
            doc.addPage(page);
            try (PDPageContentStream contents = new PDPageContentStream(doc, page)) {
                contents.drawImage(image, 0,0);     
                contents.close();

            }

下面转换为pdf到tiff

document = PDDocument.load(new File(pdfFilename));
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            BufferedImage[] images = new BufferedImage[document.getNumberOfPages()];

            for (int i = 0; i < images.length; i++) {
                PDPage page = (PDPage) document.getPage(i);
                BufferedImage image;
                try {
                    image = pdfRenderer.renderImageWithDPI(i, 300, ImageType.RGB); // its throwing outofmemory error at this line
                    images[i] = image;
                } catch (IOException e) {
                    LOGGER.error("Exception while reading merged pdf file:" + e.getMessage());
                    throw e;
                }
            }

            File tempFile = new File(tiffFileName+".tiff");
            ImageWriter writer = ImageIO.getImageWritersByFormatName("TIFF").next();
            ImageOutputStream output = ImageIO.createImageOutputStream(tempFile);
            writer.setOutput(output);
            ImageWriteParam params = writer.getDefaultWriteParam();
            params.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
            writer.prepareWriteSequence(null);
            for (int i = 0; i < images.length; i++) {
                params.setCompressionType("JPEG");
                writer.writeToSequence(new IIOImage(images[i], null, null), params);
            }
            writer.endWriteSequence();

Answer 1

要避免内存不足异常，请尝试使用合适的值传递Xms和Xmx参数来启动应用程序。请参阅此帖子What are the Xms and Xmx parameters when starting JVMs?和https://docs.oracle.com/cd/E21764_01/web.1111/e13814/jvm_tuning.htm#PERFM150：

设置初始和最小堆大小

-Xms Oracle建议将最小堆大小（-Xms）设置为等于最大堆大小（-Xmx），以最大限度地减少垃圾回收。

设置最大堆大小

-Xmx设置较低的最大堆值与实时数据量相比，通过强制频繁的垃圾收集来降低性能。

PDFBox Outofmemory在将pdf转换为Tiff时，如何压缩JPEG图像？

1 个答案: