如何使用java将PNG文件转换为PDF？

我可以使用任何开源库吗？

Answer 1

itext可以帮到你。 你没有真正将png转换为pdf，但创建了一个带有png的pdf。 简单的例子：

Document document = new Document(PageSize.A4, 20, 20, 20, 20); PdfWriter.getInstance(document, new FileOutputStream("C:/test.pdf")); document.open(); Image image = Image.getInstance(getClass().getResource("/logo.png")); document.add(image); document.close(); 

Answer 2

如果横向模式更适合，则旋转页面的示例

 /** * Converts arbitrary image file to PDF * http://stackoverflow.com/a/42937466/241986 * @param imageFile contents of JPEG or PNG file * @param outputStream stream to write out pdf, always closed after this method execution. * @throws IOException when there' an actual exception or image is not valid */ public static void imageToPdf(byte[] imageFile, OutputStream outputStream) throws IOException { try { Image image; try { image = Image.getInstance(imageFile); } catch (BadElementException bee) { throw new IOException(bee); } //See http://stackoverflow.com/questions/1373035/how-do-i-scale-one-rectangle-to-the-maximum-size-possible-within-another-rectang Rectangle A4 = PageSize.A4; float scalePortrait = Math.min(A4.getWidth() / image.getWidth(), A4.getHeight() / image.getHeight()); float scaleLandscape = Math.min(A4.getHeight() / image.getWidth(), A4.getWidth() / image.getHeight()); // We try to occupy as much space as possible // Sportrait = (w*scalePortrait) * (h*scalePortrait) // Slandscape = (w*scaleLandscape) * (h*scaleLandscape) // therefore the bigger area is where we have bigger scale boolean isLandscape = scaleLandscape > scalePortrait; float w; float h; if (isLandscape) { A4 = A4.rotate(); w = image.getWidth() * scaleLandscape; h = image.getHeight() * scaleLandscape; } else { w = image.getWidth() * scalePortrait; h = image.getHeight() * scalePortrait; } Document document = new Document(A4, 10, 10, 10, 10); try { PdfWriter.getInstance(document, outputStream); } catch (DocumentException e) { throw new IOException(e); } document.open(); try { image.scaleAbsolute(w, h); float posH = (A4.getHeight() - h) / 2; float posW = (A4.getWidth() - w) / 2; image.setAbsolutePosition(posW, posH); image.setBorder(Image.NO_BORDER); image.setBorderWidth(0); try { document.newPage(); document.add(image); } catch (DocumentException de) { throw new IOException(de); } } finally { document.close(); } } finally { outputStream.close(); } } 

在pom.xml里面，如果您还没有使用iText，那么免费的iText forks之一

  com.github.librepdf openpdf 1.0.1  

Answer 3

用于阅读javax.imageio.ImageIO以编写pdf itext： http ：//itextpdf.com