gcp_YUVcolor(3) LibGGIGCP color description

Other Alias

gcp_pixel, gcp_RGBAcolor, gcp_CMYKcolor, gcp_HSVcolor, gcp_YCCcolor


#include <ggi/gcp.h>
typedef ggi_pixel gcp_pixel;
typedef ggi_color gcp_RGBAcolor;
typedef struct { ggi_float y,u,v; } gcp_YUVcolor;
typedef struct { uint16_t c,m,y,k; } gcp_CMYKcolor;
typedef struct { ggi_float h,s,v; } gcp_HSVcolor;
typedef struct { uint16_t y,c1,c2; } gcp_YCCcolor;


Colors are described generally through display-independent gcp_RGBAcolor, gcp_YUVcolor, gcp_CMYKcolor, gcp_HSVcolor and gcp_YCCcolor structures for the RGBA, YUV, CMYK, HSV and YCC color spaces.

gcp_pixels are display-dependent pixel values. They are used by all GCP operations for efficiency. Use gcpMap*Color(3) to convert gcp_*colors to gcp_pixels.


gcp_RGBAcolor represents the rgba colorspace and is the same as ggi_color(3).

gcp_YUVcolor represents the YUV colorspace. It consists of y, u and v. They correspond to the luminance and chrominance components.

gcp_CMYKcolor represents the CMYK colorspace. It consists of c, m, y and k. They correspond to the cyan, magenta, yellow and black channels.

gcp_HSVcolor represents the HSV colorspace. It consists of h, s and v. They correspond to the hue, saturation and velocity.

gcp_YCCcolor, better known as Kodak PhotoCD. It consists of y, c1 and c2.

gcp_pixels format depends on the actual display and mode. For those who want to operate directly on pixel values, this format is described in the ggi_pixelformat(3) structure.


Although individual pixels are kept into 32 bits gcp_pixel, arrays of pixels, as used in ggi[Get|Put]* functions, gcpPack*Colors and gcpUnpack*Pixels, are stored in the display specific format, thus packed according to the actual pixel size. This size is given by the GT_SIZE macro for graphtype or the size field of the ggi_pixelformat(3) structure.

The buffers provided to these functions must be big enough to store or read enough pixels. Although it is safe to use 32 bits per pixel, the optimum size (in bits) can be calculated by multiplying the number of pixel by their size. Don't forget to round up to a multiple of 8 to get the number of bytes.

If you want to access such buffers directly, do not use pointer arithmetics with gcp_pixels.