What is the color value range?

Colors are stored as R, G, B triplets. With meshes, each color value is a floating point (single or double precision) in the range [0.0 ; 1.0]. With point clouds, each color value is a 8 bits unsigned int in the range [0 ; 255].

The filters that apply to both meshes and point clouds may have to convert between the two different ranges of color value. For example, the Copy Graph filter filter can copy a mesh to a point cloud (and vice versa) with its vertex colors. So it must convert colors to suit the range of color values supported by the target data structure.

To make it easier to write such filters, some convenient functions that do the conversion have been put into the dedicated color_conversion.hpp file. The conversion functions use the syntax:

OutputType convert_color_value< OutputType >(InputType value)

The conversion is based on the type of the color value passed as a parameter, and the type of the value returned by the function. For example, a conversion from type 'uint8_t' to type 'float' will transform the color value from the range [0 ; 255] to the range [0.0 ; 1.0]. If the input type and the output type match the same range, then the color value is not changed. In this case, only a cast is applied to produce the right output type.

Examples:

// convert color to range [0.0 ; 1.0]
// if color is already in the target range, values are casted without change
FPColor color_0_1(FEVV::Math::convert_color_value< float >(color[0]),
                  FEVV::Math::convert_color_value< float >(color[1]),
                  FEVV::Math::convert_color_value< float >(color[2]));

// convert color to range [0 ; 255]
// if color is already in the target range, values are casted without change
UInt8Color color_0_255(FEVV::Math::convert_color_value< uint8_t >(color[0]),
                       FEVV::Math::convert_color_value< uint8_t >(color[1]),
                       FEVV::Math::convert_color_value< uint8_t >(color[2]));