Colormaps and Colors: GDK 2 Reference Manual

## Colormaps and Colors Colormaps and Colors — Manipulation of colors and colormaps |

## Functions

GdkColormap * | gdk_colormap_new ()
GdkColormap * | gdk_colormap_ref ()
void | gdk_colormap_unref ()
GdkColormap * | gdk_colormap_get_system ()
gint | gdk_colormap_get_system_size ()
void | gdk_colormap_change ()
gint | gdk_colormap_alloc_colors ()
gboolean | gdk_colormap_alloc_color ()
void | gdk_colormap_free_colors ()
void | gdk_colormap_query_color ()
GdkVisual * | gdk_colormap_get_visual ()
GdkScreen * | gdk_colormap_get_screen ()
void | gdk_colors_store ()
GdkColor * | gdk_color_copy ()
void | gdk_color_free ()
gint | gdk_colors_alloc ()
void | gdk_colors_free ()
gint | gdk_color_white ()
gint | gdk_color_black ()
gboolean | gdk_color_parse ()
gint | gdk_color_alloc ()
gint | gdk_color_change ()
gboolean | gdk_color_equal ()
guint | gdk_color_hash ()
gchar * | gdk_color_to_string ()

## Types and Values

| GdkColor
| GdkColormap

## Includes

    #include <gdk/gdk.h>

## Description

These functions are used to modify colormaps. A colormap is an object that contains the mapping between the color values stored in memory and the RGB values that are used to display color values. In general, colormaps only contain significant information for pseudo-color visuals, but even for other visual types, a colormap object is required in some circumstances.

There are a couple of special colormaps that can be retrieved. The system colormap (retrieved with `gdk_colormap_get_system()`) is the default colormap of the system. If you are using GdkRGB, there is another colormap that is important - the colormap in which GdkRGB works, retrieved with `gdk_rgb_get_colormap()`. However, when using GdkRGB, it is not generally necessary to allocate colors directly.

In previous revisions of this interface, a number of functions that take a GdkColormap parameter were replaced with functions whose names began with "gdk_colormap_". This process will probably be extended somewhat in the future - `gdk_color_white()`, `gdk_color_black()`, and `gdk_color_change()` will probably become aliases.

## Functions

### gdk_colormap_new ()

    GdkColormap *
    gdk_colormap_new (GdkVisual *visual,
                      gboolean allocate);

Creates a new colormap for the given visual.

#### Parameters

visual | a GdkVisual. |
allocate | if `TRUE`, the newly created colormap will be a private colormap, and all colors in it will be allocated for the applications use. |

#### Returns

the new GdkColormap.

### gdk_colormap_ref ()

    GdkColormap *
    gdk_colormap_ref (GdkColormap *cmap);

`gdk_colormap_ref` has been deprecated since version 2.0 and should not be used in newly-written code.

Use `g_object_ref()` instead.

Deprecated function; use `g_object_ref()` instead.

#### Parameters

cmap | a GdkColormap |

#### Returns

the colormap

### gdk_colormap_unref ()

    void
    gdk_colormap_unref (GdkColormap *cmap);

`gdk_colormap_unref` has been deprecated since version 2.0 and should not be used in newly-written code.

Use `g_object_unref()` instead.

Deprecated function; use `g_object_unref()` instead.

#### Parameters

cmap | a GdkColormap |

### gdk_colormap_get_system ()

    GdkColormap *
    gdk_colormap_get_system (void);

Gets the system's default colormap for the default screen. (See `gdk_colormap_get_system_for_screen()`)

#### Returns

the default colormap.

### gdk_colormap_get_system_size ()

    gint
    gdk_colormap_get_system_size (void);

`gdk_colormap_get_system_size` is deprecated and should not be used in newly-written code.

Returns the size of the system's default colormap. (See the description of struct GdkColormap for an explanation of the size of a colormap.)

#### Returns

the size of the system's default colormap.

### gdk_colormap_change ()

    void
    gdk_colormap_change (GdkColormap *colormap,
                         gint ncolors);

`gdk_colormap_change` is deprecated and should not be used in newly-written code.

Changes the value of the first `ncolors` in a private colormap to match the values in the `colors` array in the colormap. This function is obsolete and should not be used. See `gdk_color_change()`.

#### Parameters

colormap | a GdkColormap. |
ncolors | the number of colors to change. |

### gdk_colormap_alloc_colors ()

    gint
    gdk_colormap_alloc_colors (GdkColormap *colormap,
                               GdkColor *colors,
                               gint n_colors,
                               gboolean writeable,
                               gboolean best_match,
                               gboolean *success);

Allocates colors from a colormap.

#### Parameters

colormap | a GdkColormap. |
colors | The color values to allocate. On return, the pixel values for allocated colors will be filled in. |
n_colors | The number of colors in `colors` . |
writeable | If `TRUE`, the colors are allocated writeable (their values can later be changed using `gdk_color_change()`). Writeable colors cannot be shared between applications. |
best_match | If `TRUE`, GDK will attempt to do matching against existing colors if the colors cannot be allocated as requested. |
success | An array of length `ncolors` . On return, this indicates whether the corresponding color in `colors` was successfully allocated or not. |

#### Returns

The number of colors that were not successfully allocated.

### gdk_colormap_alloc_color ()

    gboolean
    gdk_colormap_alloc_color (GdkColormap *colormap,
                              GdkColor *color,
                              gboolean writeable,
                              gboolean best_match);

Allocates a single color from a colormap.

#### Parameters

colormap | a GdkColormap. |
color | the color to allocate. On return the `pixel` field will be filled in if allocation succeeds. |
writeable | If `TRUE`, the color is allocated writeable (their values can later be changed using `gdk_color_change()`). Writeable colors cannot be shared between applications. |
best_match | If `TRUE`, GDK will attempt to do matching against existing colors if the color cannot be allocated as requested. |

#### Returns

`TRUE` if the allocation succeeded.

### gdk_colormap_free_colors ()

    void
    gdk_colormap_free_colors (GdkColormap *colormap,
                              const GdkColor *colors,
                              gint n_colors);

Frees previously allocated colors.

#### Parameters

colormap | a GdkColormap. |
colors | the colors to free. |
n_colors | the number of colors in `colors` . |

### gdk_colormap_query_color ()

    void
    gdk_colormap_query_color (GdkColormap *colormap,
                              gulong pixel,
                              GdkColor *result);

Locates the RGB color in `colormap` corresponding to the given hardware pixel `pixel` . `pixel` must be a valid pixel in the colormap; it's a programmer error to call this function with a pixel which is not in the colormap. Hardware pixels are normally obtained from `gdk_colormap_alloc_colors()`, or from a GdkImage. (A GdkImage contains image data in hardware format, a GdkPixbuf contains image data in a canonical 24-bit RGB format.)

This function is rarely useful; it's used for example to implement the eyedropper feature in GtkColorSelection.

#### Parameters

colormap | a GdkColormap |
pixel | pixel value in hardware display format |
result | GdkColor with red, green, blue fields initialized |

### gdk_colormap_get_visual ()

    GdkVisual *
    gdk_colormap_get_visual (GdkColormap *colormap);

Returns the visual for which a given colormap was created.

#### Parameters

colormap | a GdkColormap. |

#### Returns

the visual of the colormap.

### gdk_colormap_get_screen ()

    GdkScreen *
    gdk_colormap_get_screen (GdkColormap *cmap);

Gets the screen for which this colormap was created.

#### Parameters

cmap | a GdkColormap |

#### Returns

the screen for which this colormap was created.

Since: 2.2

### gdk_colors_store ()

    void
    gdk_colors_store (GdkColormap *colormap,
                      GdkColor *colors,
                      gint ncolors);

`gdk_colors_store` is deprecated and should not be used in newly-written code.

Changes the value of the first `ncolors` colors in a private colormap. This function is obsolete and should not be used. See `gdk_color_change()`.

#### Parameters

colormap | a GdkColormap. |
colors | the new color values. |
ncolors | the number of colors to change. |

### gdk_color_copy ()

    GdkColor *
    gdk_color_copy (const GdkColor *color);

Makes a copy of a color structure. The result must be freed using `gdk_color_free()`.

#### Parameters

color | a GdkColor. |

#### Returns

a copy of `color` .

### gdk_color_free ()

    void
    gdk_color_free (GdkColor *color);

Frees a color structure created with `gdk_color_copy()`.

#### Parameters

color | a GdkColor. |

### gdk_colors_alloc ()

    gint
    gdk_colors_alloc (GdkColormap *colormap,
                      gboolean contiguous,
                      gulong *planes,
                      gint nplanes,
                      gulong *pixels,
                      gint npixels);

`gdk_colors_alloc` is deprecated and should not be used in newly-written code.

Allocates colors from a colormap. This function is obsolete. See `gdk_colormap_alloc_colors()`. For full documentation of the fields, see the Xlib documentation for ``XAllocColorCells()``.

#### Parameters

colormap | a GdkColormap. |
contiguous | if `TRUE`, the colors should be allocated in contiguous color cells. |
planes | an array in which to store the plane masks. |
nplanes | the number of planes to allocate. (Or zero, to indicate that the color allocation should not be planar.) |
pixels | an array into which to store allocated pixel values. |
npixels | the number of pixels in each plane to allocate. |

#### Returns

`TRUE` if the allocation was successful

### gdk_colors_free ()

    void
    gdk_colors_free (GdkColormap *colormap,
                     gulong *pixels,
                     gint npixels,
                     gulong planes);

`gdk_colors_free` is deprecated and should not be used in newly-written code.

Frees colors allocated with `gdk_colors_alloc()`. This function is obsolete. See `gdk_colormap_free_colors()`.

#### Parameters

colormap | a GdkColormap. |
pixels | the pixel values of the colors to free. |
npixels | the number of values in `pixels` . |
planes | the plane masks for all planes to free, OR'd together. |

### gdk_color_white ()

    gint
    gdk_color_white (GdkColormap *colormap,
                     GdkColor *color);

`gdk_color_white` is deprecated and should not be used in newly-written code.

Returns the white color for a given colormap. The resulting value has already allocated been allocated.

#### Parameters

colormap | a GdkColormap. |
color | the location to store the color. |

#### Returns

`TRUE` if the allocation succeeded.

### gdk_color_black ()

    gint
    gdk_color_black (GdkColormap *colormap,
                     GdkColor *color);

`gdk_color_black` is deprecated and should not be used in newly-written code.

Returns the black color for a given colormap. The resulting value has already been allocated.

#### Parameters

colormap | a GdkColormap. |
color | the location to store the color. |

#### Returns

`TRUE` if the allocation succeeded.

### gdk_color_parse ()

    gboolean
    gdk_color_parse (const gchar *spec,
                     GdkColor *color);

Parses a textual specification of a color and fill in the `red`, `green`, and `blue` fields of a GdkColor structure. The color is not allocated, you must call `gdk_colormap_alloc_color()` yourself. The string can either one of a large set of standard names. (Taken from the X11 `rgb.txt` file), or it can be a hex value in the form '#rgb' '#rrggbb' '#rrrgggbbb' or '#rrrrggggbbbb' where 'r', 'g' and 'b' are hex digits of the red, green, and blue components of the color, respectively. (White in the four forms is '#fff' '#ffffff' '#fffffffff' and '#ffffffffffff')

#### Parameters

spec | the string specifying the color. |
color | the GdkColor to fill in. | [out]

#### Returns

`TRUE` if the parsing succeeded.

### gdk_color_alloc ()

    gint
    gdk_color_alloc (GdkColormap *colormap,
                     GdkColor *color);

`gdk_color_alloc` has been deprecated since version 2.2 and should not be used in newly-written code.

Use `gdk_colormap_alloc_color()` instead.

Allocates a single color from a colormap.

#### Parameters

colormap | a GdkColormap. |
color | The color to allocate. On return, the `pixel` field will be filled in. |

#### Returns

`TRUE` if the allocation succeeded.

### gdk_color_change ()

    gint
    gdk_color_change (GdkColormap *colormap,
                      GdkColor *color);

`gdk_color_change` is deprecated and should not be used in newly-written code.

Changes the value of a color that has already been allocated. If `colormap` is not a private colormap, then the color must have been allocated using `gdk_colormap_alloc_colors()` with the `writeable` set to `TRUE`.

#### Parameters

colormap | a GdkColormap. |
color | a GdkColor, with the color to change in the `pixel` field, and the new value in the remaining fields. |

#### Returns

`TRUE` if the color was successfully changed.

### gdk_color_equal ()

    gboolean
    gdk_color_equal (const GdkColor *colora,
                     const GdkColor *colorb);

Compares two colors.

#### Parameters

colora | a GdkColor. |
colorb | another GdkColor. |

#### Returns

`TRUE` if the two colors compare equal

### gdk_color_hash ()

    guint
    gdk_color_hash (const GdkColor *colora);

A hash function suitable for using for a hash table that stores GdkColor's.

#### Parameters

colora | a GdkColor. |

#### Returns

The hash function applied to `colora`

### gdk_color_to_string ()

    gchar *
    gdk_color_to_string (const GdkColor *color);

Returns a textual specification of `color` in the hexadecimal form `#rrrrggggbbbb`, where `r`, `g` and `b` are hex digits representing the red, green and blue components respectively.

#### Parameters

color | a GdkColor |

#### Returns

a newly-allocated text string

Since: 2.12

## Types and Values

### GdkColor

    typedef struct {
      guint32 pixel;
      guint16 red;
      guint16 green;
      guint16 blue;
    } GdkColor;

The GdkColor structure is used to describe an allocated or unallocated color.

#### Members

guint32 `pixel`; | For allocated colors, the value used to draw this color on the screen. |
guint16 `red`; | The red component of the color. This is a value between 0 and 65535, with 65535 indicating full intensitiy. |
guint16 `green`; | The green component of the color. |
guint16 `blue`; | The blue component of the color. |

### GdkColormap

    typedef struct {
      gint      GSEAL (size);
      GdkColor *GSEAL (colors);
    } GdkColormap;

The colormap structure contains the following public fields.