Auto scaling of Images with iTextSharp

Question

I’m generating PDF files from my C# 4.0 windows application using iTextSharp API. I’ll be passing HTML string which will contain Rich Text and Images. My PDF file size is A4 with default margins. Noticed that when I have a large image in dimension (e.g. height="701px" width="935px") , the image is not coming to PDF. Looks like, I have to scale down the image dimension which should be able to fit in the PDF A4 size. I checked this by pasting the image to a word document of A4 size, MS Word automatically scales down the image by 36% i.e. MS Word takes only 64% of the original image dimension and sets the absolute height & width.

Can someone please help to mimic similar behavior in C#?

Let me know how to automatically set an image height & width to fit in A4 PDF file.

Answer 1

That's correct, iTextSharp won't automatically size images that are too big for the document. So it's just a matter of:

• Calculating available document width and height with left/right and top/bottom page margins.
• Getting the image width and height.
• Comparing the document's width and height with the image's width and height.
• Scaling the image if needed.

Here's one way, see inline comments:

// change this to any page size you want    
Rectangle defaultPageSize = PageSize.A4;   
using (Document document = new Document(defaultPageSize)) {
  PdfWriter.GetInstance(document, STREAM);
  document.Open();
// if you don't account for the left/right margins, the image will
// run off the current page
  float width = defaultPageSize.Width
    - document.RightMargin
    - document.LeftMargin
  ;
  float height = defaultPageSize.Height
    - document.TopMargin
    - document.BottomMargin
  ;
  foreach (string path in imagePaths) {
    Image image = Image.GetInstance(path);
    float h = image.ScaledHeight;
    float w = image.ScaledWidth;
    float scalePercent;
// scale percentage is dependent on whether the image is 
// 'portrait' or 'landscape'        
    if (h > w) {
// only scale image if it's height is __greater__ than
// the document's height, accounting for margins
      if (h > height) {
        scalePercent = height / h;
        image.ScaleAbsolute(w * scalePercent, h * scalePercent);
      }
    }
    else {
// same for image width        
      if (w > width) {
        scalePercent = width / w;
        image.ScaleAbsolute(w * scalePercent, h * scalePercent);
      }
    }
    document.Add(image);
  }
}

The only point worth noting is that imagePaths above is a string[] so that you can test what happens when adding a collection of images that are to big to fit in a page.

Another way is to put the image in a one column, single cell PdfPTable:

PdfPTable table = new PdfPTable(1);
table.WidthPercentage = 100;
foreach (string path in imagePaths) {
  Image image = Image.GetInstance(path);
  PdfPCell cell = new PdfPCell(image, true);
  cell.Border = Rectangle.NO_BORDER;
  table.AddCell(cell);
}
document.Add(table);