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GimpColorSpace

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

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.

Functions

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.

Parameters

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.

Parameters

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.

Parameters

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

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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].

Parameters

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].

Parameters

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].

Parameters

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].

Parameters

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.

Parameters

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.

Parameters

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

Parameters

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].

Parameters

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);

Parameters

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);

Parameters

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)

 

Types and Values

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