There are several different ways to control the chart’s output from the Chart FX server control. One, is to simply allow the browser detection feature generate the appropriate format suitable for the requesting client.

You may also instruct Chart FX to render graphs in a variety of formats. Configuring the chart to do so may also be accomplished several different ways.

As a server control, Chart FX supports a method called RenderToStream that allows the developer to select, among other things, the type of desired output for your charts. By default, Chart FX will generate a PNG image of the chart if you do not specify the type, and call the RenderToStream method. The RenderFormat and OutputWriter properties may also be used to render charts in the desired format:

Note:

The OutputWriter property is normally reserved to configure external output writers for a chart.

What Output Formats can Chart FX Generate?

Examining the RenderToStream definition carefully, you'll notice that PNG, JPEG, SVG and Flash are all possible parameters (instead of simply "Image"). This means Chart FX is capable of generating any of these file formats. The SVG and Flash formats require adding a reference to appropriate image writer library in your project. Once a reference has been added, you may then configure the RenderFormat , RenderToStream or OutputWriter member accordingly. With extensibility in mind, future output writers may always be added as future requirements demand.

.NET Client Controls

Format: .NET format.

Comments: Component is required on the browser.

Full managed code, no signatures are required.

Interactivity: Full interactivity (including user toolbar).

Accessibility: Windows .NET clients only.

Generating charts as .NET Client Controls allows users to interact with the chart through a variety of tools and context menus. This chart format allows the end users to customize the visual attributes as well as modify data values directly in the chart. In order for client computers to view these types of charts, the .NET Framework must be installed as well as the appropriate .NET security settings applied for the zone of the chart that is being accessed.

When setting the RenderToStream or RenderFormat members to “Auto", Chart FX will use environment variables received from the client to determine if this format is supported. If so, the .NET Client control will be used to view the chart requested.

PNG Images

Format: Raster format.

Comments: Best image format for producing charts.

Interactivity: Provides limited interactivity through image maps.

Accessibility: Supported in most current browsers.

The PNG algorithm is particularly effective for drawing vector images (such as charts), as images will experience no quality degradation or color dithering. This format came as a response to Unisys prohibiting the public distribution of the GIF generation algorithm. This format is even better in terms of quality and compression than GIF and supports many more features, such as transparency, interlaced, 24-bit palettes and many other advantages over GIF images.

This means, PNG is the preferred image format for Chart FX. However, the drawback is that many older browsers do not support this image format (As a matter of fact, only browsers 4.x and above can display PNG images). Therefore, the JPEG format is also available for these older browsers.

JPEG Images

Format: Raster format.

Comments: Slightly faster than PNG, however charts are not as crisp.

Interactivity: No interactivity.

Accessibility: Universal access.

This format was created to compress and display photo quality images (not vector images such as charts). As a result, displaying charts using this algorithm is not advisable as you will obtain quality degradation and color dithering when creating JPEG images.

When you set the third parameter of the RenderToStream method to "Image" you are basically instructing Chart FX to determine the most appropriate image format. This is particularly important as PNG images will be generated whenever possible achieving best results in the majority of browsers. Whenever a PNG image can't be generated, Chart FX will generate a JPEG image.

Additional Output Writers

The SVG and Flash writers are additional writers supported by Chart FX. With this extensible methodology, other output writers may also be added in the future.

SVG

Format: Vector format.

Pros: Enhances performance significantly; files are small and painted on the client.

Cons: Limited interactivity.

Accessibility: Accessible from many platforms.

DHTML

Format: Dynamic HTML with client side script for generating menus, options, etc.

Pros: Does not require special client side technology to produce an interactive chart as other interactive formats may require.

Cons: Interactivity is slightly limited due to the limitations of DHTML over other dynamic formats.

Accessibility: Accessible from many platforms.

Flash

Format: Flash Macromedia format.

Pros: Charts are downloaded and viewed using a widely available 3rd party Flash viewer at the client.

Cons: Limited interactivity.

Accessibility: Accessible from many platforms.

Accessibility

Format: Renders chart as text.

Pros: Comply with the Section 508 of the Rehabilitation Act. Many accessibility browsers can read chart information to a user.

Cons: Limited chart interpretation.

Accessibility: Requires supported Accessibility tools (Browser).

Note: Due to Microsoft's decision to change the security settings for .NET components (Search for "Trustworthy Computing" at the Microsoft site), Software FX, Inc. has decided Chart FX should generate an image by default instead of a .NET component. You can easily adopt the .NET component generation behavior by changing the third parameter of the RenderToStream call to ".NET" or "Auto" or change the RenderFormat property at design time on the Web Forms project.

Forcing the Chart FX Server to Generate Images

In order to force Chart FX to always generate images, you must configure the RenderToStream method and prevent the automatic Browser Detection capability. By modifying the third parameter of the RenderToStream method to "Image", the Chart FX Server component will always generate images no matter which browser type is accessing the page. Once again, this is also possible using the RenderFormat property:

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