WPF/WinForms/GDI interop: converting a WriteableBitmap to a System.Drawing.Image?

Question

How can I convert a WPF WriteableBitmap object to a System.Drawing.Image?

My WPF client app sends bitmap data to a web service, and the web service needs to construct a System.Drawing.Image on that end.

I know I can get the data of a WriteableBitmap, send the info over to the web service:

// WPF side:

WriteableBitmap bitmap = ...;
int width = bitmap.PixelWidth;
int height = bitmap.PixelHeight;
int[] pixels = bitmap.Pixels;

myWebService.CreateBitmap(width, height, pixels);

But on the web service end, I don't know how to create a System.Drawing.Image from this data.

// Web service side:

public void CreateBitmap(int[] wpfBitmapPixels, int width, int height)
{
   System.Drawing.Bitmap bitmap = ? // How can I create this?
}

Raleighraley

Answer 1

this blog post shows how to encode your WriteableBitmap as a jpeg image. Perhaps that helps?

If you really want to transfer the raw image data (pixels) you could:

1. create a System.Drawing.Bitmap with the correct size
2. iterate over your raw data, convert the raw data to a System.Drawing.Color (e.g. via Color.FromArgb() and set each pixel color in the newly created image via SetPixel()

I'd definitely prefer the first solution (the one described in the blog post).

Sonny

Thanks. I'll play around and see if any of this helps. – Raleighraley

Answer 2

If your bitmap data is uncompressed, you could probably use this System.Drawing.Bitmap constructor: Bitmap(Int32, Int32, Int32, PixelFormat, IntPtr).

If the bitmap is encoded as jpg or png, create a MemoryStream from the bitmap data, and use it with the Bitmap(Stream) constructor.

EDIT:

Since you're sending the bitmap to a web service, I suggest you encode it to begin with. There are several encoders in the System.Windows.Media.Imaging namespace. For example:

    WriteableBitmap bitmap = ...;
    var stream = new MemoryStream();               
    var encoder = new JpegBitmapEncoder(); 
    encoder.Frames.Add( BitmapFrame.Create( bitmap ) ); 
    encoder.Save( stream ); 
    byte[] buffer = stream.GetBuffer(); 
    // Send the buffer to the web service   

On the receiving end, simply:

    var bitmap = new System.Drawing.Bitmap( new MemoryStream( buffer ) );

Hope that helps.

Odel

My data is simply wpfWriteableBitmap.Pixels, which returns an int[] – Raleighraley

I've updated my answer with an example of how to encode the bitmap before you send it, and how to decode it in the web service. – Luthuli

Answer 3

The question is for WPF, and Pixels does not appear to be a property of WriteableBitmap. Some of the answers here point to SilverLight articles, so I suspect this might be a difference between WPF and SilverLight.

Glogau