phsl2rgb

Synopsis

Description

phsl2rgb converts color image from the color space HSL (Hue, Saturation, Lightness) to the color space RGB (Red, Green, Blue).

A hue refers to the gradation of color within the visible spectrum, or optical spectrum, of light. It is expressed in degree unit [0..360].

Saturation or purity is the intensity of a specific hue: a highly saturated hue has a vivid, intense color, while a less saturated hue appears more muted and gray. With no saturation at all, the hue becomes a shade of gray. It is expressed as percentage [0..100].

Lightness is the amount of light in a color. It is expressed in gray level unit [0..255].

The conversion uses the following transformation:

q= | l * (1 + s)     if l <  1/2
   | l + s - (l * s) if l >= 1/2

p = 2 * l - q

t_k = t / 360

t_R = t_k+1/3
t_V = t_k
t_B = t_k-1/3

for each C in {R,V,B}
  if t_C < 0 : t_C = t_C + 1.0
  if t_C > 1 : t_C = t_C - 1.0

      | p + ((q - p) * 6 * t_C)           if t_C <1/6
      | q                                 if 1/6 <= T_C <1/2
  C = | p + ((q - p) * 6 * (2 / 3 - T_C)) if 1/2 <= T_C < 2/3
      | p                                 else

Inputs

• im_in: a HSL color image.

Outputs

• im_out: a RGB color image.

Result

Returns SUCCESS or FAILURE.

Examples

Converts parrot.pan from rgb to hsl and conversely:

   prgb2hsl parrot.pan a.pan
   phsl2rgb a.pan b.pan

See also

C++ prototype