Name

pe_setup_pseudo_colr − Creates an array of colors of constant hue and saturation but varying luminance, and sets the weight vector. 

Operating States: PHOP, WSOP, ∗, ∗
Digital PHIGS extension function

Syntax

void pe_setup_pseudo_colr (
  Pint                 wsid,      /∗ (I) Workstation identifier ∗/
  Pcolr_rep           ∗colours,   /∗ (I) Input color value in red, green,
                                         and blue (RGB) ∗/
  Ppseudo_approx_rec  ∗datarec    /∗ (M) Computed data record ∗/
)

Data Structures

typedef union {
    Prgb        rgb;       /∗ red, green, and blue color specification ∗/
    Pcieluv     cieluv;    /∗ CIELUV color specification ∗/
    Phls        hls;       /∗ hue, lightness, and saturation color
                              specification ∗/
    Phsv        hsv;       /∗ hue, saturation, and value color
                              specification ∗/
    Pdata       unsupp;    /∗ color in an unsupported color model ∗/
    int         impl_dep;  /∗ implementation-defined ∗/
} Pcolr_rep;
    typedef struct {
        Pfloat   red;     /∗ red intensity   ∗/
        Pfloat   green;   /∗ green intensity ∗/
        Pfloat   blue;    /∗ blue intensity  ∗/
    } Prgb;
    typedef struct {
        Pfloat   cieluv_x;      /∗ x coefficient ∗/
        Pfloat   cieluv_y;      /∗ y coefficient ∗/
        Pfloat   cieluv_y_lum;  /∗ y luminance ∗/
    } Pcieluv;
    typedef struct {
        Pfloat   hue;        /∗ hue ∗/
        Pfloat   lightness;  /∗ lightness ∗/
        Pfloat   satur;      /∗ saturation ∗/
    } Phls;
    typedef struct {
        Pfloat   hue;    /∗ hue ∗/
        Pfloat   satur;  /∗ saturation ∗/
        Pfloat   value;  /∗ value ∗/
    } Phsv;
    typedef struct {
        size_t   size;   /∗ size of data ∗/
        void    ∗data;   /∗ pointer to the data ∗/
    } Pdata;
typedef struct {               /∗ pseudo color approximation  ∗/
    Pint        range;         /∗ number of colors ∗/
    Pfloat      weight[3];     /∗ weight vector ∗/
    Pint        model;         /∗ color model ∗/
    Pcolr_rep  ∗colr;          /∗ color map ∗/
} Ppseudo_apprfqox_rec;

Description

pe_setup_pseudo_colr creates an array of colors of constant hue and saturation but varying in luminance from dark to light, and sets the weight vector as appropriate.  The function returns the color map and the weight vector in the data record.  Digital PHIGS generates the color map by holding constant the hue and saturation of colors and varying the luminance from 0.0 to 1.0.  Digital PHIGS sets the weight vector to (one-third, one-third, one-third). 

Digital PHIGS applies the weight vector to the resultant color in the output pipeline after the lighting and shading phase in the following manner:

    luminance = red_component ∗ weight(0) +
    blue_component ∗ weight(1) +
    green_component ∗ weight(2)

Digital PHIGS uses the luminance from the previous equation as an index into the pseudo color map for the final color. 

The application can install the color map by calling the pe_set_pseudo_colr function.