作者：fyupeng
技术专栏：☞ https://github.com/fyupeng
项目地址：☞ https://github.com/fyupeng/distributed-blog-system-api
留给读者
咱们又见面了，本期带给大家什么，请往下看，绝对是干货！
一、介绍
提供 PDF文件二进制参数，返回删除空白页的PDF文件二进制。
二、代码
引入依赖：
<dependency><groupId>org.apache.pdfbox</groupId><artifactId>pdfbox</artifactId><version>2.0.21</version>
</dependency>
代码：
public static void main(String[] args) throws IOException {File file = new File("d:/hztzs.pdf");byte[] bytes = new byte[(int) file.length()];FileInputStream fis = new FileInputStream(file);fis.read(bytes);bytes = new ArchivElecFileService().removeEmptyPages(bytes);File newfile = new File("d:/out.pdf");FileOutputStream fos = new FileOutputStream(newfile);fos.write(bytes);}public byte[] removeEmptyPages(byte[] fileBytes) throws IOException {// Load the PDF documentPDDocument document = PDDocument.load(fileBytes);// Iterate through each pagePDPageTree pages = document.getPages();int pageCount = document.getNumberOfPages();for (int i = pageCount - 1; i >= 0; i--) {// Extract text from the pagePDFTextStripper stripper = new PDFTextStripper();stripper.setStartPage(i + 1); // Page indexes are 1-based in PDFTextStripperstripper.setEndPage(i + 1);String text = stripper.getText(document);PDPage page = pages.get(i);// Check if the page is emptyif (text.trim().isEmpty()) {// Remove the pageif (isPageImageOnly(page, document)) {document.removePage(i);}}}// 保存结果文件ByteArrayOutputStream outputStream = new ByteArrayOutputStream();document.save(outputStream);return outputStream.toByteArray();}private static boolean isPageImageOnly(PDPage page, PDDocument document) throws IOException {PDFRenderer renderer = new PDFRenderer(document);BufferedImage image = renderer.renderImageWithDPI(document.getPages().indexOf(page), 300); // Adjust DPI as neededreturn isImageOnly(image);}private static boolean isImageOnly(BufferedImage image) {// Check if the image contains significant content (e.g., not just white)// You can implement custom logic based on your requirements// For simplicity, here's a basic checkint width = image.getWidth();int height = image.getHeight();long whitePixelCount = ImageUtils.countWhitePixels(image);// If more than 90% of the image is white, consider it emptydouble whiteRatio = (double) whitePixelCount / (width * height);return whiteRatio > 0.95; // Adjust threshold as needed}// Utility class to count white pixels in an imagestatic class ImageUtils {public static long countWhitePixels(BufferedImage image) {long count = 0;int width = image.getWidth();int height = image.getHeight();for (int y = 0; y < height; y++) {for (int x = 0; x < width; x++) {int pixel = image.getRGB(x, y);if (isWhite(pixel)) {count++;}}}return count;}private static boolean isWhite(int pixel) {// Define your white color threshold based on RGB values// Adjust as per your image characteristicsint red = (pixel >> 16) & 0xff;int green = (pixel >> 8) & 0xff;int blue = (pixel) & 0xff;return red > 250 && green > 250 && blue > 250;}}三、总结
易用、高效、轻便！
