GimpColorSpace

GimpColorSpace — Utility functions which convert colors between different color models.

Synopsis

void                gimp_rgb_to_hsv                     (const GimpRGB *rgb,
                                                         GimpHSV *hsv);
void                gimp_rgb_to_hsl                     (const GimpRGB *rgb,
                                                         GimpHSL *hsl);
void                gimp_rgb_to_cmyk                    (const GimpRGB *rgb,
                                                         gdouble pullout,
                                                         GimpCMYK *cmyk);
void                gimp_hsv_to_rgb                     (const GimpHSV *hsv,
                                                         GimpRGB *rgb);
void                gimp_hsl_to_rgb                     (const GimpHSL *hsl,
                                                         GimpRGB *rgb);
void                gimp_cmyk_to_rgb                    (const GimpCMYK *cmyk,
                                                         GimpRGB *rgb);
void                gimp_rgb_to_hwb                     (const GimpRGB *rgb,
                                                         gdouble *hue,
                                                         gdouble *whiteness,
                                                         gdouble *blackness);
void                gimp_hwb_to_rgb                     (gdouble hue,
                                                         gdouble whiteness,
                                                         gdouble blackness,
                                                         GimpRGB *rgb);
void                gimp_rgb_to_hsv_int                 (gint *red,
                                                         gint *green,
                                                         gint *blue);
void                gimp_hsv_to_rgb_int                 (gint *hue,
                                                         gint *saturation,
                                                         gint *value);
void                gimp_rgb_to_hsl_int                 (gint *red,
                                                         gint *green,
                                                         gint *blue);
void                gimp_rgb_to_cmyk_int                (gint *red,
                                                         gint *green,
                                                         gint *blue,
                                                         gint *pullout);
void                gimp_cmyk_to_rgb_int                (gint *cyan,
                                                         gint *magenta,
                                                         gint *yellow,
                                                         gint *black);
gint                gimp_rgb_to_l_int                   (gint red,
                                                         gint green,
                                                         gint blue);
void                gimp_hsl_to_rgb_int                 (gint *hue,
                                                         gint *saturation,
                                                         gint *lightness);
void                gimp_rgb_to_hsv4                    (const guchar *rgb,
                                                         gdouble *hue,
                                                         gdouble *saturation,
                                                         gdouble *value);
void                gimp_hsv_to_rgb4                    (guchar *rgb,
                                                         gdouble hue,
                                                         gdouble saturation,
                                                         gdouble value);

Description

When programming pixel data manipulation functions you will often use algorithms operating on a color model different from the one GIMP uses. This file provides utility functions to convert colors between different color spaces.

Details

gimp_rgb_to_hsv ()

void                gimp_rgb_to_hsv                     (const GimpRGB *rgb,
                                                         GimpHSV *hsv);

Does a conversion from RGB to HSV (Hue, Saturation, Value) colorspace.

rgb :

A color value in the RGB colorspace

hsv :

The value converted to the HSV colorspace

gimp_rgb_to_hsl ()

void                gimp_rgb_to_hsl                     (const GimpRGB *rgb,
                                                         GimpHSL *hsl);

Convert an RGB color value to a HSL (Hue, Saturation, Lightness) color value.

rgb :

A color value in the RGB colorspace

hsl :

The value converted to HSL

gimp_rgb_to_cmyk ()

void                gimp_rgb_to_cmyk                    (const GimpRGB *rgb,
                                                         gdouble pullout,
                                                         GimpCMYK *cmyk);

Does a naive conversion from RGB to CMYK colorspace. A simple formula that doesn't take any color-profiles into account is used. The amount of black pullout how can be controlled via the pullout parameter. A pullout value of 0 makes this a conversion to CMY. A value of 1 causes the maximum amount of black to be pulled out.

rgb :

A value in the RGB colorspace

pullout :

A scaling value (0-1) indicating how much black should be pulled out

cmyk :

The input value naively converted to the CMYK colorspace

gimp_hsv_to_rgb ()

void                gimp_hsv_to_rgb                     (const GimpHSV *hsv,
                                                         GimpRGB *rgb);

Converts a color value from HSV to RGB colorspace

hsv :

A color value in the HSV colorspace

rgb :

The returned RGB value.

gimp_hsl_to_rgb ()

void                gimp_hsl_to_rgb                     (const GimpHSL *hsl,
                                                         GimpRGB *rgb);

Convert a HSL color value to an RGB color value.

hsl :

A color value in the HSL colorspace

rgb :

The value converted to a value in the RGB colorspace

gimp_cmyk_to_rgb ()

void                gimp_cmyk_to_rgb                    (const GimpCMYK *cmyk,
                                                         GimpRGB *rgb);

Does a simple transformation from the CMYK colorspace to the RGB colorspace, without taking color profiles into account.

cmyk :

A color value in the CMYK colorspace

rgb :

The value converted to the RGB colorspace

gimp_rgb_to_hwb ()

void                gimp_rgb_to_hwb                     (const GimpRGB *rgb,
                                                         gdouble *hue,
                                                         gdouble *whiteness,
                                                         gdouble *blackness);

Theoretically, hue 0 (pure red) is identical to hue 6 in these transforms. Pure red always maps to 6 in this implementation. Therefore UNDEFINED can be defined as 0 in situations where only unsigned numbers are desired.

RGB are each on [0, 1]. Whiteness and Blackness are returned in the range [0, 1] and H is returned in the range [0, 6]. If W == 1 - B, H is undefined.

rgb :

A color value in the RGB colorspace

hue :

The hue value of the above color, in the range 0 to 6

whiteness :

The whiteness value of the above color, in the range 0 to 1

blackness :

The blackness value of the above color, in the range 0 to 1

gimp_hwb_to_rgb ()

void                gimp_hwb_to_rgb                     (gdouble hue,
                                                         gdouble whiteness,
                                                         gdouble blackness,
                                                         GimpRGB *rgb);

H is defined in the range [0, 6] or UNDEFINED, B and W are both in the range [0, 1]. The returned RGB values are all in the range [0, 1].

hue :

A hue value, in the range 0 to 6

whiteness :

A whiteness value, in the range 0 to 1

blackness :

A blackness value, in the range 0 to 1

rgb :

The above color converted to the RGB colorspace

gimp_rgb_to_hsv_int ()

void                gimp_rgb_to_hsv_int                 (gint *red,
                                                         gint *green,
                                                         gint *blue);

The arguments are pointers to int representing channel values in the RGB colorspace, and the values pointed to are all in the range [0, 255].

The function changes the arguments to point to the HSV value corresponding, with the returned values in the following ranges: H [0, 359], S [0, 255], V [0, 255].

red :

The red channel value, returns the Hue channel

green :

The green channel value, returns the Saturation channel

blue :

The blue channel value, returns the Value channel

gimp_hsv_to_rgb_int ()

void                gimp_hsv_to_rgb_int                 (gint *hue,
                                                         gint *saturation,
                                                         gint *value);

The arguments are pointers to int, with the values pointed to in the following ranges: H [0, 360], S [0, 255], V [0, 255].

The function changes the arguments to point to the RGB value corresponding, with the returned values all in the range [0, 255].

hue :

The hue channel, returns the red channel

saturation :

The saturation channel, returns the green channel

value :

The value channel, returns the blue channel

gimp_rgb_to_hsl_int ()

void                gimp_rgb_to_hsl_int                 (gint *red,
                                                         gint *green,
                                                         gint *blue);

The arguments are pointers to int representing channel values in the RGB colorspace, and the values pointed to are all in the range [0, 255].

The function changes the arguments to point to the corresponding HLS value with the values pointed to in the following ranges: H [0, 360], L [0, 255], S [0, 255].

red :

Red channel, returns Hue channel

green :

Green channel, returns Lightness channel

blue :

Blue channel, returns Saturation channel

gimp_rgb_to_cmyk_int ()

void                gimp_rgb_to_cmyk_int                (gint *red,
                                                         gint *green,
                                                         gint *blue,
                                                         gint *pullout);

Does a naive conversion from RGB to CMYK colorspace. A simple formula that doesn't take any color-profiles into account is used. The amount of black pullout how can be controlled via the pullout parameter. A pullout value of 0 makes this a conversion to CMY. A value of 100 causes the maximum amount of black to be pulled out.

red :

the red channel; returns the cyan value (0-255)

green :

the green channel; returns the magenta value (0-255)

blue :

the blue channel; returns the yellow value (0-255)

pullout :

the percentage of black to pull out (0-100); returns the black value (0-255)

gimp_cmyk_to_rgb_int ()

void                gimp_cmyk_to_rgb_int                (gint *cyan,
                                                         gint *magenta,
                                                         gint *yellow,
                                                         gint *black);

Does a naive conversion from CMYK to RGB colorspace. A simple formula that doesn't take any color-profiles into account is used.

cyan :

the cyan channel; returns the red value (0-255)

magenta :

the magenta channel; returns the green value (0-255)

yellow :

the yellow channel; returns the blue value (0-255)

black :

the black channel (0-255); doesn't change

gimp_rgb_to_l_int ()

gint                gimp_rgb_to_l_int                   (gint red,
                                                         gint green,
                                                         gint blue);

Calculates the lightness value of an RGB triplet with the formula L = (max(R, G, B) + min (R, G, B)) / 2

red :

Red channel

green :

Green channel

blue :

Blue channel

Returns :

Luminance vaue corresponding to the input RGB value

gimp_hsl_to_rgb_int ()

void                gimp_hsl_to_rgb_int                 (gint *hue,
                                                         gint *saturation,
                                                         gint *lightness);

The arguments are pointers to int, with the values pointed to in the following ranges: H [0, 360], L [0, 255], S [0, 255].

The function changes the arguments to point to the RGB value corresponding, with the returned values all in the range [0, 255].

hue :

Hue channel, returns Red channel

saturation :

Saturation channel, returns Green channel

lightness :

Lightness channel, returns Blue channel

gimp_rgb_to_hsv4 ()

void                gimp_rgb_to_hsv4                    (const guchar *rgb,
                                                         gdouble *hue,
                                                         gdouble *saturation,
                                                         gdouble *value);

rgb :

RGB triplet, rgb[0] is red channel, rgb[1] is green, rgb[2] is blue (0..255)

hue :

Pointer to hue channel (0..1)

saturation :

Pointer to saturation channel (0..1)

value :

Pointer to value channel (0..1)

gimp_hsv_to_rgb4 ()

void                gimp_hsv_to_rgb4                    (guchar *rgb,
                                                         gdouble hue,
                                                         gdouble saturation,
                                                         gdouble value);

rgb :

RGB triplet, rgb[0] is red channel, rgb[1] is green, rgb[2] is blue (0..255)

hue :

Hue channel (0..1)

saturation :

Saturation channel (0..1)

value :

Value channel (0..1)