Watermarking jpg files in C#

Question

I am trying to watermark a jpg image with another jpg image. It's working fine if I store the resulting image as a new image. Is it possible to just update the original image file with the watermark image? I don't need to store it as a different file.

Here is my code:

//watermark image 

Bitmap sizedImg = (Bitmap)System.Drawing.Image.FromFile(@"C:\report branding.jpg");

//original file

System.Drawing.Bitmap template=(System.Drawing.Bitmap)System.Drawing.Image.FromFile(@"C:\CentralUtahCombined1.jpg");            


 Graphics g = Graphics.FromImage(template);
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                g.DrawImage(sizedImg, new Point(template.Width - sizedImg.Width,
                             template.Height - sizedImg.Height));


            //watermarking the image but saving it as a different image file - here if I //provide the name as the original file name, it throws an error
            string myFilename = @"C:\CentralUtah.jpg";

            template.Save(myFilename);


            template.Dispose();
            sizedImg.Dispose();
            g.Flush();

What is the exception thrown? – Danny Beckett Mar 19 '13 at 23:29 — Danny Beckett, Mar 19 '13 at 23:29

Nick VanderPyle · Answer 1 · 2013-03-19T23:47:33.483

3

Image.FromFile retains a lock on the original file. Rather than create the image directly from the file, try opening the file from a FileStream and creating the image from that stream. This way you can control when the file's lock is released.

try this:

public static Image CreateImage(string filePath)
{
    using(var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        return Image.FromStream(fs);
}

A bit more info. MSDN mentions that Image.FromFile will retain the lock until the image is disposed. http://msdn.microsoft.com/en-us/library/stf701f5.aspx

I just realized that the FromStream method suggests that the stream remain open. If you still have problems, try reading the bytes into a memorystream. In this example, the memorystream isn't disposed. It would be a good idea to dispose of the stream when you've adapted this to your code. :)

public static Image CreateImage(string filePath)
{
        var bytes = File.ReadAllBytes(filePath);
        var ms = new MemoryStream(bytes);
        return Image.FromStream(ms);
}

edited Mar 19 '13 at 23:47

answered Mar 19 '13 at 23:31

Nick VanderPyle

2,939
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This will not work, because the `Image.FromStream` needs the stream to not be disposed. – Jens Granlund Mar 19 '13 at 23:38
Clone the image in memory or create and write it to a new Image. Then you can dispose the original and save over it. – Eric Falsken Mar 19 '13 at 23:43
@JensGranlund You caught my mistake. :) I had just noticed that in the msdn when you commented. – Nick VanderPyle Mar 19 '13 at 23:50
@EricFalsken You should post that as an answer with a short example. Sounds like it might be a better answer. – Nick VanderPyle Mar 19 '13 at 23:51
@NickVanderPyle, Looks like you did good on your own. Congrats. – Eric Falsken Mar 20 '13 at 06:09
Thanks for sharing your ideas. Reading the bytes into memory stream and then created the bitmap solved the problem. Thanks – Mahtta Namita Mar 21 '13 at 19:59

score 1 · Answer 2 · edited May 23 '17 at 12:04

1

It is probably because Image.FromFile method is locking the file.
See this answer for a method on how to load the file without locking it: https://stackoverflow.com/a/3389126/214222

edited May 23 '17 at 12:04

Community

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1

answered Mar 19 '13 at 23:33

Jens Granlund

4,950
1
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Watermarking jpg files in C#

2 Answers2