C API

library(colorfast)

{colorfast} exports three C functions for use in other packages.

To use these functions:

In your package DESCRIPTION
- Add LinkingTo: colorfast
- Add Depends: colorfast (>= 1.0.1)
In your C code
- Add #include <colorfast.h>
- Call the functions below

void col_to_rgb(const char *col, uint8_t ptr[4]);
uint32_t col_to_int(const char *col); 
void int_to_col(uint32_t icol, char buf[10]);

String color to vector of RGBA values

void col_to_rgb(const char *col, uint8_t ptr[4])

const char *col is a pointer to a null-terminated C string containing either a hex color, or the name of a standard R color: E.g. "#1287Af", "hotpink"
uint8_t ptr[4] holds the values returned from the function i.e. RGBA color component values

The R call col_to_rgb('red'), can be called via the C api as:

#include <stdint.h>
#include <colorfast.h>

void convert_col_to_rgb(const char *col) {
  uint8_t values[4];
  col_to_rgb(col, values);
  
  for (int i = 0; i < 4; ++i) {
    printf("%i ", values[i]);
  }
}

String color to packed integer color

void col_to_int(const char *col)

const char *col is a pointer to a null-terminated C string containing either a hex color, or the name of a standard R color: E.g. "#1287Af", "hotpink"

#include <stdint.h>
#include <colorfast.h>

void convert_col_to_int(const char *col) {
  uint32_t value = col_to_int(col);
  
  printf("%i ", value);
}

Packed integer color to hexadecimal color

void int_to_col(uint32_t icol, char buf[10])

uint32_t icol unsigned integer holding the 4 RGBA color values
char buf[10] a character buffer into which the hex color will be written e.g. #1154EE00

#include <stdint.h>
#include <colorfast.h>

void convert_int_to_col(uint32_t icol) {
  char buf[10];
  int_to_col(icol, buf);
  
  printf("%s\n", buf);
}