How to (correctly) copy a chart to the clip board?

[Adam Petaccia]

I would like to enable users to copy a chart to the clipboard, preserving appearance and transparency, so I've chosen to use PNG as the format.

PngBitmapEncoder bitmapEncoder = new System.Windows.Media.Imaging.PngBitmapEncoder ();
var chartPicture = currChart.Save (96, 96, bitmapEncoder);
PngBitmapDecoder bitmapDecoder = new PngBitmapDecoder (chartPicture, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);

Clipboard.SetImage (bitmapDecoder.Frames[0]);

However, when I paste from the clipboard, all of the transparent areas are black, which is not desirable. I don't have much experience with clip board operations, so perhaps I am doing something wrong, though other than the transparency is seem so work fine. Is there a way I can accomplish this either and either preserve the chart's transparency or at least grabbing a rendering of the chart using its current background (almost always white)?

[Yavor]

Hi Adam Petaccia,

 Clipboard supports only bitmap images. Because bitmap images don't have alpha channel, the transparency is replaced with black color. To fix this you can change the background from transparent to something else, for example - white color. Taking this into account your code can look like this:

RadChart1.Background = Brushes.White;

BmpBitmapEncoder bitmapEncoder = new System.Windows.Media.Imaging.BmpBitmapEncoder();

System.IO.Stream chartPicture = RadChart1.Save(96, 96, bitmapEncoder);

chartPicture.Seek(0, System.IO.SeekOrigin.Begin);

BmpBitmapDecoder bitmapDecoder = new BmpBitmapDecoder(chartPicture, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);

Clipboard.SetImage(bitmapDecoder.Frames[0]);



Regards,
Yavor Ivanov
the Telerik team

[Tony]

Hi Yavor,

I am attempting to use the code you suggested but am running into the following error regarding the last line of code:

ChartCtrl chartControl = (ChartCtrl)elementHost1.Child;
            chartControl.radChart.Background = System.Windows.Media.Brushes.White;
            BmpBitmapEncoder bitmapEncoder = new System.Windows.Media.Imaging.BmpBitmapEncoder();
            System.IO.Stream chartPicture = chartControl.radChart.Save(96, 96, bitmapEncoder);
            chartPicture.Seek(0, System.IO.SeekOrigin.Begin);
            BmpBitmapDecoder bitmapDecoder = new BmpBitmapDecoder(chartPicture, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
Clipboard.SetImage(bitmapDecoder.Frames[0]);

The best overloaded method match for 'System.Windows.Forms.Clipboard.SetImage(System.Drawing.Image)' has some invalid arguments.


I'm attempting to call it from a windows form but using an elementhost to connect to the specific radchart. I'm not sure how to resolve this.

Thanks

Tony

[Martin Ivanov]

Hi Tony,

It seems that the compile time error appears because your are using the System.Windows.Forms.Clipboard.SetImage() method, which expects an object of type System.Drawing.Image. However, the bitmapDecoder.Frames[0] element is of type System.Windows.Media.Imaging.BitmapSource and it cannot be passed to the method.

The example given by Yavor uses the WPF's Clipboard class which is located in the System.Windows namespace.

In order to copy the chart as an image in the clipboard you can try the following approaches:

• Create a System.Drawing.Image object from the stream returned by the chart's Save() method and then pass it to the WinForms' Clipboard.SetImage() method.
  

  var img = System.Drawing.Image.FromStream(chartPicture);
  System.Windows.Forms.Clipboard.SetImage(img);

• Use the System.Windows.Cliboard.SetImage() method instead of the WinForms clipboard.
  

  System.Windows.Clipboard.SetImage(bitmapDecoder.Frames[0]);

There is also an approach that you can use to save the image (along its transparency) as a stream. Basically you can get the stream with the image and use the System.Windows.Cliboard.SetDataObject() method. If the application that gets the stream from the clipboard implement a logic for reading images saved in this manner (as Word for example), the picture will be pasted correctly. Here is an example in code:

using (var stream = new MemoryStream())
{
    Telerik.Windows.Media.Imaging.ExportExtensions.ExportToImage(chartControl.radChart, stream, new PngBitmapEncoder());
    var data = new DataObject("PNG", stream);
    Clipboard.SetDataObject(data, true);
}

I hope this works for you.

Regards,
Martin
Telerik

 

 

[Tony]

Thanks for your reply. This works.