Scaled image blurry in PDFBox

Question

I'm trying to scaling an image with size = 2496 x 3512 into a PDF document. I'm using PDFBox to generate it but the scaled image ends up blurred.

Here are some snippets:

• PDF Page size (A4) returned by page.findMediaBox().createDimension(): java.awt.Dimension[width=612,height=792]

• Then I calculate the scaled dimension based on the Page size vs. Image size which returns: java.awt.Dimension[width=562,height=792] I use the code below in order to calculate the scaled dimension:

  public static Dimension getScaledDimension(Dimension imgSize, Dimension boundary) {
    int original_width = imgSize.width;
    int original_height = imgSize.height;
    int bound_width = boundary.width;
    int bound_height = boundary.height;
    int new_width = original_width;
    int new_height = original_height;
  
    // first check if we need to scale width
    if (original_width > bound_width) {
      //scale width to fit
      new_width = bound_width;
      //scale height to maintain aspect ratio
      new_height = (new_width * original_height) / original_width;
    }
  
    // then check if we need to scale even with the new height
    if (new_height > bound_height) {
      //scale height to fit instead
      new_height = bound_height;
      //scale width to maintain aspect ratio
      new_width = (new_height * original_width) / original_height;
    }
  
    return new Dimension(new_width, new_height);
  }
  

• And to actually perform the image scaling I'm using Image Scalr API:

  BufferedImage newImg = Scalr.resize(img, Scalr.Method.ULTRA_QUALITY, Scalr.Mode.FIT_EXACT, 
    scaledWidth, scaledHeight, Scalr.OP_ANTIALIAS);
  

My question is what am I doing wrong? A big image shouldn't be blurred when scaled to a smaller size. Is this something related to the PDF page resolution/size?

Thank you,

Gyo

Answer 1

Ok, I found a way to add images without losing the quality.

Actually to make the image not be blurred I let PDFBox to resize the image by giving it the desired size. Like the code below:

PDXObjectImage ximage = new PDJpeg(doc, new FileInputStream(new File("/usr/gyo/my_large_image.jpg")), 1.0f);
PDPageContentStream contentStream = new PDPageContentStream(doc, page, true, false);
Dimension scaledDim = getScaledDimension(new Dimension(ximage.getWidth(),  ximage.getHeight()), page.getMediaBox().createDimension());
contentStream.drawXObject(ximage, 1, 1, scaledDim.width, scaledDim.height);
contentStream.close();

Thank you,

Gyo