You must be trying to export the chart with transparent background as Jpg due to which you are getting a black background. Please note that Jpg doesn’t support transparency. You have to set some background color in chart. PNG supports transparency but unfortunately Visifire doesn’t support exporting chart as PNG. If you are working in WPF, then you will be able to save the chart with transparent background as PNG.

For Example

onClick
{
chart.height=500;
chart.width=800;

// show save dialog
}

This save the chart with old size, not with the changed size.

Please checkout the following links.

http://forums.silverlight.net/forums/p/190369/438871.aspx
http://forums.silverlight.net/forums/t/5774.aspx
http://forums.silverlight.net/forums/p/83989/195479.aspx
http://forums.silverlight.net/forums/p/180353/406915.aspx

I am using silverlight.
I need to use visifire chart image in pdf file along with other details. [Currently I am creating pdf file in web application in .aspx file]
Is there any way to do this?

@Dave, If you are working with Silverlight then you have to export chart using save file dialog only. But if you are working with WPF, then you can export the chart without using save file dialog also. Please follow the documentation sample below:
http://www.visifire.com/documentation/Visifire_Documentation/Common_Tasks/Exporting_Chart_toImage_using_Managed_Code_in_WPF.htm

@smaran, If you are working with WPF, then you can export the chart without rendering it. Please check out the example present in the documentation below:
http://www.visifire.com/documentation/Visifire_Documentation/Common_Tasks/Exporting_Chart_as_Image_without_Rendering.htm

Regarding your second query, If you are working with Silverlight then the exported image size will be the same as chart size. But if you are working with WPF, you can save the chart image in a different size than the actual chart size. Please follow the documentation sample below:
http://www.visifire.com/documentation/Visifire_Documentation/Common_Tasks/Exporting_Chart_toImage_using_Managed_Code_in_WPF.htm

In this sample, you just have to set proper size and dpi values while creating a bitmap as shown below:
RenderTargetBitmap renderBitmap = new RenderTargetBitmap( (int)surface.Width + 250, (int)surface.Height + 200, 120d, 120d, PixelFormats.Pbgra32);

1.Always only the chart rendered can be exported.I am not able to export a chart created in managed code.

2.If the chart is made resizeable to screen then the exported image also changes. Not able to set size of chart.

You can export an image in a standard ASP.NET project if you make your own SilverLight control and pass in the VisiFire XAML through JavaScript and deserialize the XAML into a chart object within the Silverlight control. Once you have the Chart rendered, you can follow the steps in the blog post to export the image.

So you have two Silverlight controls on your ASP.NET form. One is VisiFire’s and the other is yours. Its basically the same as how the VisiFire works.

Thanks,
Steven McWhorter