Convert pdf to images

[sabraMa]

Hello
I have some questions:
1 Could I convert my pdf document( multipages) to png images with OpenPDF ?
2 Is it possible to generate pdfA format ?
3 there is any way to compress exsiting pdf ?

thank you a lot for your help

[doobo]

This is my method of rewriting. I hope it will be useful！

     /**
	 * 根据总页数,按照perSize页生成一张长图片的逻辑, 进行拆分
	 * @param in
	 * @param perSize
	 * @return
	 */
	public static List<byte[]> pdfToImage(byte[] in, Integer perSize) {
		List<byte[]> bms = new ArrayList<>();
		try {
			/*图像合并使用参数*/
			// 定义宽度
			int width = 0;
			// 保存一张图片中的RGB数据
			int[] singleImgRGB;
			// 定义高度，后面用于叠加
			int shiftHeight = 0;
			//保存每张图片的像素值
			BufferedImage imageResult = null;
			// 利用PdfBox生成图像
			PDDocument pdDocument = PDDocument.load(in);
			PDFRenderer renderer = new PDFRenderer(pdDocument);
			/*根据总页数, 按照50页生成一张长图片的逻辑, 进行拆分*/
			// 每50页转成1张图片
			perSize = perSize == null? 1: perSize;
			// 总计循环的次数
			int totalCount = getPages(pdDocument.getNumberOfPages(), perSize);
			for (int m = 0; m < totalCount; m++) {
				for (int i = 0; i < perSize; i++) {
					int pageIndex = i + (m * perSize);
					if (pageIndex == pdDocument.getNumberOfPages()) {
						break;
					}
					// 144为图片的dpi，dpi越大，则图片越清晰，图片越大，转换耗费的时间也越多
					BufferedImage image = renderer.renderImageWithDPI(pageIndex, 144, ImageType.RGB);
					int imageHeight = image.getHeight();
					int imageWidth = image.getWidth();
					if (i == 0) {
						//计算高度和偏移量
						//使用第一张图片宽度;
						width = imageWidth;
						// 保存每页图片的像素值
						// 加个判断：如果m次循环后所剩的图片总数小于pageLength，则图片高度按剩余的张数绘制，否则会出现长图片下面全是黑色的情况
						if ((pdDocument.getNumberOfPages() - m * perSize) < perSize) {
							imageResult = new BufferedImage(width, imageHeight * (pdDocument.getNumberOfPages() - m * perSize), BufferedImage.TYPE_INT_RGB);
						} else {
							imageResult = new BufferedImage(width, imageHeight * perSize, BufferedImage.TYPE_INT_RGB);
						}
					} else {
						// 将高度不断累加
						shiftHeight += imageHeight;
					}
					singleImgRGB = image.getRGB(0, 0, width, imageHeight, null, 0, width);
					imageResult.setRGB(0, shiftHeight, width, imageHeight, singleImgRGB, 0, width);
				}
				// image转byte[]
				ByteArrayOutputStream byteArrayOutputStream = new  ByteArrayOutputStream();
				ImageIO.write(imageResult, "png", byteArrayOutputStream);
				byteArrayOutputStream.flush();
				bms.add(byteArrayOutputStream.toByteArray());
				byteArrayOutputStream.close();
				// 写图片
				//File outFile = new File(pdfPath.replace(".pdf", "_" + m + ".jpg"));
				//ImageIO.write(imageResult, "jpg", outFile);
				shiftHeight = 0;
			}
			pdDocument.close();
		} catch (Exception e) {
			log.error("pdf转图片异常", e);
		}
		return bms;
	}

        /*
	 * 计算总页数
	 */
	private static int getPages(int counts, int pageSize) {
		if(counts == 0) {
			return 0;
		} else if (counts <= pageSize) {
			return 1;
		} else if (counts%pageSize!=0) {
			return counts / pageSize + 1;
		} else {
			return counts / pageSize;
		}
	}

[andreasrosdal]

Thanks for sharing! Can you please submit this code as a pull request to OpenPDF? Create a new Java class for it. Then we can add this as a new useful high-level function in the library.

[asturio]

This is a nice one for anybody wanting to contribute.

• Grab the code of Convert pdf to images #346 (comment)
• Create some new utility class for that method
• clean the code a little bit (my chinese is not that good :-) )
• write some Unit-Test
• Create a Pull Request

[GreenToad]

This code uses Apache PDFBox not LibrePDF

[asturio]

Just answering 2 questions:

2. Yes, OpenPDF can generate PDF/A
3. I'm not aware of any part of OpenPDF for compressing existing PDFs. There are some other nice (non-Java) tools which can manipulate Postscript and PDF. Maybe Ghostscript is a away to do so.

[mluppi]

@asturio The labels good first issue and task could probably be removed from this issue. The code is for Apache PDFBox and I don't see an easy way to just add that functionality. This issue does not need continuous attention as #145 and #152 which have the task label.

[bhupendersinghh]

Hi @zengleo did you make changes to add this functionality?

[ObsisMc]

Hi, is there anyone working on this issue? Can I take it?

[andreasrosdal]

Sure, please submit a pull request for this.
@ObsisMc