Chapter 7. Format Conversion

Programmers of all kinds always ask for information on how to convert between file formats, and graphics programmers are no exception. You must realize, however, that not every format can be converted to every other format, and this is doubly so if you wish to preserve image quality.

Contents:
Is It Really Possible?
Don't Do It If You Don't Need to ...
...But If You Do
Other Format Conversion Considerations

Is It Really Possible?

The biggest problems occur when you attempt to convert between files of different basic format types--bitmap to vector, for instance. Successful conversion between basic format types is not always possible due to the great differences in the ways data is stored.

File conversion is a thankless task for any number of reasons. No vendor, for instance, feels obligated to disclose revisions to proprietary formats, or even to publish accurate and timely specifications for the ones already in common use. Many formats also have obscure variants which may be difficult to track down. At any moment, too, a revision to a major application may appear, containing a bug which makes it produce incorrect files. These files will ever after need to be supported. For all these reasons, think long and hard about any decision you make about whether to include file conversion features in your application. Remember, too, that a format that is reasonably well designed for a particular intended application cannot necessarily be converted for use with another application. Interchange between devices and applications is only as good as the software components (readers and writers) which generate and interpret the format, whether it is CGM, PostScript, or any other format.