Generic Image Library : channel_convert

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# channel_convert
[Algorithms and Utility Functions]

## Detailed Description

Converting from one channel type to another

Conversion is done as a simple linear mapping of one channel range to the other, such that the minimum/maximum value of the source maps to the minimum/maximum value of the destination. One implication of this is that the value 0 of signed channels may not be preserved!

When creating new channel models, it is often a good idea to provide specializations for the channel conversion algorithms, for example, for performance optimizations. If the new model is an integral type that can be signed, it is easier to define the conversion only for the unsigned type (`channel_converter_unsigned`) and provide specializations of `detail::channel_convert_to_unsigned` and `detail::channel_convert_from_unsigned` to convert between the signed and unsigned type.

Example:

    // bits32f is a floating point channel with range [0.0f ... 1.0f]
    bits32f src_channel = channel_traits<bits32f>::max_value();
    assert(src_channel == 1);

    // bits8 is 8-bit unsigned integral channel (typedef-ed from unsigned char)
    bits8 dst_channel = channel_convert<bits8>(src_channel);
    assert(dst_channel == 255);     // max value goes to max value

## Modules

| channel_converter_unsigned
| Convert one unsigned/floating point channel to another. Converts both the channel type and range.

## Classes

struct | channel_converter
| A unary function object converting between channel types. More...
struct | default_channel_converter
| Same as channel_converter, except it takes the destination channel by reference, which allows us to move the templates from the class level to the method level. This is important when invoking it on heterogeneous pixels. More...

## Functions

template<typename DstChannel, typename SrcChannel>
channel_traits< DstChannel >::value_type | boost::gil::channel_convert (SrcChannel src)
| Converting from one channel type to another.