How to Convert Image to Pdf

JPG to PDF Convertor in C#

iTextSharp does it pretty cleanly and is open source. Also, it has a very good accompanying book by the author which I recommend if you end up doing more interesting things like managing forms. For normal usage, there are plenty resources on mailing lists and newsgroups for samples of how to do common things.

EDIT: as alluded to in @Chirag's comment, @Darin's answer has code that definitely compiles with current versions.

~~Example usage:~~

public static void ImagesToPdf(string[] imagepaths, string pdfpath)
{
    using(var doc = new iTextSharp.text.Document())
    {
        iTextSharp.text.pdf.PdfWriter.GetInstance(doc, new FileStream(pdfpath, FileMode.Create));
        doc.Open();
        foreach (var item in imagepaths)
        {
            iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(item);
            doc.Add(image);
        }
    }
}

Convert image to pdf fail by unknow file extension

Another yet way to do things that makes use the pathlib module which allows file and folder paths to be tried as objects and manipulated via an object-oriented programming paradigm or model — which often results in very concise code:

from pathlib import Path
from PIL import Image

path = Path('./images')
exts = {'.jpg', '.jpeg', '.png', '.bmp', '.tif', '.tiff'}

for path_object in path.glob('**/*'):
    if path_object.is_file() and path_object.suffix in exts:
        img = Image.open(path_object)
        img = img.convert('RGB')
        img.save(path_object.parent / (path_object.stem+'.pdf'))

C# - How to convert an image to a PDF (using a free library)

I've come up with a way to do this using PDFSharp, hopefully will be useful for others as well.

        // Convert to PDF and delete image
        PdfHelper.Instance.SaveImageAsPdf($"{fileName}.png", $"{fileName}.pdf", 1000, true);

The new class:

using System.IO;
using PdfSharp.Drawing;
using PdfSharp.Pdf;  

public sealed class PdfHelper
{
    private PdfHelper()
    {
    }

    public static PdfHelper Instance { get; } = new PdfHelper();

    internal void SaveImageAsPdf(string imageFileName, string pdfFileName, int width = 600, bool deleteImage = false)
    {
        using (var document = new PdfDocument())
        {
            PdfPage page = document.AddPage();
            using (XImage img = XImage.FromFile(imageFileName))
            {
                // Calculate new height to keep image ratio
                var height = (int)(((double)width / (double)img.PixelWidth) * img.PixelHeight);

                // Change PDF Page size to match image
                page.Width = width;
                page.Height = height;

                XGraphics gfx = XGraphics.FromPdfPage(page);
                gfx.DrawImage(img, 0, 0, width, height);                
            }
            document.Save(pdfFileName);
        }

    if (deleteImage)            
        File.Delete(imageFileName);
    }
}