Windows Media Photo provides native support for both RGB and CMYK, providing a reversible color transform for each of these color formats to an internal luminance-dominant format used for optimal compression efficiency. In addition Windows Media Photo supports monochrome and arbitrary n-channel color formats.
Because the transforms employed are fully reversible, the codec supports both lossless and lossy operation using a single algorithm. This significantly simplifies the implementation for embedded applications and provides capabilities not typically found in other compressed image file formats.
Windows Media Photo supports a wide range of popular numerical encodings at multiple bit depths. 8-bit and 16-bit formats, as well as some specialized packed bit formats, are supported for both lossy and lossless compression. 32-bit formats are only supported using lossy compression as only 24 bits are typically retained through the various transforms designed to achieve maximum compression efficiency. While Windows Media Photo uses integer arithmetic exclusively for its internal processing, an innovative color transform process provides lossless encoding support for both fixed and floating point image information. This also enables extremely efficient conversion between different color formats as part of the encode/decode process.
Today’s file formats for continuous tone images present many limitations in maintaining the highest image quality or delivering the most optimal system performance. Windows Media Photo was designed to remove these limitations. The design objectives include:
- High performance, embedded system friendly compression
- Small memory footprint
- Simple, integer-only operations (no divides)
- Industry-leading compression quality
- Lossless or lossy compression using the same algorithm
- Support a very wide range of pixel formats:
- Monochrome, RGB, CMYK or n-Channel image representation
- 8 or 16-bit unsigned integer
- 16 or 32-bit signed integer
- 16 or 32-bit floating point
- Several packed bit formats
- 1bpc monochrome
- 5 or 10bpc RGB
- RGBE Radiance
- Simple, extensible TIFF-like container structure
- Planar or interleaved alpha channel
- Embedded ICC Profile
- EXIF and XMP metadata