Apple Patent Blocking PNG Development

Daniel writes: "Apple has a patent (U.S. Patent No. 5,379,129) on compositing a source and destination image using a mask image. This patent appears to read on alpha channel transparency, which the PNG and MNG file formats use. APPLE has declared in their patent statement to the Scalable Vector Graphics Working Group that their patent is only available for RAND Licensing. Since this patent appears to read on the PNG file format, Apple is hampering work on the PNG and MNG file formats. Perhaps Apple would like to clarify this situation by explicitly stating that this patent does not cover the PNG and MNG file formats or by RF Licensing their patent to the PNG and MNG development groups. Alternatively, the PNG and MNG developers are asking people to submit prior art in order to invalidate Apple's patent. SGI in particular appears to have prior art with their 'blendfunction.' Make sure the prior art you submit is older than May 08, 1992, the filing date of Apple's patent."