How can I convert an RGB integer to the corresponding RGB tuple (R,G,B)?

Question

How can I convert an ARGB integer to the corresponding ARGB tuple (A,R,G,B)?

I receive some XML where a color tag is given with some integer value (e.g -16777216). I need to draw a rectangle filled with that color. But I am unable to retrieve values of the A,R,G,B components from the integer value.

Answer 1

You can try use unions. Something like this

struct color
{
  unsigned char alpha:8;
  unsigned char r:8;
  unsigned char g:8;
  unsigned char b:8;
};

union
{
  struct color selector;
  unsigned int base:32;
};

Answer 2

Use bitwise AND and shift right to select individual bytes from the 32-bit integer.

uint32_t color = -16777216;

uint8_t b = (color & 0x000000ff);
uint8_t g = (color & 0x0000ff00) >> 8;
uint8_t r = (color & 0x00ff0000) >> 16;
uint8_t a = (color & 0xff000000) >> 24;

Answer 3

If the integer is ARGB I think it should be:

unsigned char b = color & 0x000000FF;
unsigned char g = (color>> 8) & 0x000000FF;
unsigned char r = (color>>16) & 0x000000FF;
unsigned char a = (color>>24) & 0x000000FF;