jp2_channels

Provides a uniform, simplified interface to the information associated with the JP2 "Component Mapping" and "Channel Definition" boxes, the JPX "Opacity" box and, to a limited extent, the JPX "Codestream Registration" box, as well as implementing the default bindings which apply where one or more of these boxes is missing. Together, this information serves to identify the relationship between each "colour" reproduction channel of a JP2 image (or a JPX compositing layer) and the underlying code-stream image components which generate it.

Reproduction channels may be grouped into the following three categories:

• Colour intensity channels, the number of which depends upon the colour space: 1 for monochrome; 3 for RGB and related colour spaces; 4 for CMYK; etc.
• Opacity channels, often called alpha channels. A separate opacity channel may be defined for each colour intensity channel, although they will often all be the same.
• Pre-multiplied opacity channels (sometimes called pre-multiplied alpha). Again, each colour intensity channel may have its own distinct pre-multiplied opacity channels.

The actual interpretation of the colour intensity channels in terms of a specific colour space is provided by "Colour Specification" boxes, whose contents are managed by the jp2_colour interface.

Objects of this class are merely interfaces to an internal object, which cannot be directly created by an application. Creation and destruction of the internal object, as well as saving and reading of the associated JP2 boxes are capabilities reserved for the internal machinery associated with the file format manager which provides the interface.

Objects which can provide a non-empty jp2_channels interface include jp2_source, jp2_target, jpx_layer_source, jpx_layer_target, mj2_video_source and mj2_video_target.

jp2_channels (2 forms)

exists {Java: Exists}

operator!

copy {Java: Copy}

init {Java: Init}

set_colour_mapping {Java: Set_colour_mapping}

set_opacity_mapping {Java: Set_opacity_mapping}

set_premult_mapping {Java: Set_premult_mapping}

set_chroma_key {Java: Set_chroma_key}

get_num_colours {Java: Get_num_colours}

get_colour_mapping {Java: Get_colour_mapping}

get_opacity_mapping {Java: Get_opacity_mapping}

get_premult_mapping {Java: Get_premult_mapping}

get_chroma_key {Java: Get_chroma_key}