Generic Image Library: channel_convert

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Topics | Classes | Functions
channel_convert
Channel » Algorithms and Utility Functions

Converting from one channel type to another. More...

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

## Classes
struct | channel_converter< SrcChannelV, DstChannelV >
| 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>
auto | channel_convert (SrcChannel const &src) -> typename channel_traits< DstChannel >::value_type
| Converting from one channel type to another.

## 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:

// float32_t is a floating point channel with range [0.0f ... 1.0f]
float32_t src_channel = channel_traits<float32_t>::max_value();
assert(src_channel == 1);
// uint8_t is 8-bit unsigned integral channel (aliased from unsigned char)
uint8_t dst_channel = channel_convert<uint8_t>(src_channel);
assert(dst_channel == 255); // max value goes to max value
boost::gil::channel_convert
auto channel_convert(SrcChannel const &src) -> typename channel_traits< DstChannel >::value_type
Converting from one channel type to another.
Definition channel_algorithm.hpp:461
boost::gil::float32_t
scoped_channel_value< float, float_point_zero< float >, float_point_one< float > > float32_t
32-bit floating point channel type with range [0.0f ... 1.0f]. Models ChannelValueConcept
Definition typedefs.hpp:153