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  1. #include <iostream>
  2. #include <stdexcept>
  3.  
  4. #define GET_COMPONENT(color, index) (((0xFF << (index * 8)) & color) >> (index * 8))
  5.  
  6. unsigned int get_component(unsigned int color, unsigned int index)
  7. {
  8.     const unsigned int shift = index * 8;
  9.     const unsigned int mask = 0xFF << shift;
  10.     return (color & mask) >> shift;
  11. }
  12.  
  13. enum color_component
  14. {
  15.     A,B,G,R
  16. };
  17.  
  18. unsigned int get_component(unsigned int color, color_component component)
  19. {
  20.     switch (component)
  21.     {
  22.         case R:
  23.         case G:
  24.         case B:
  25.         case A:
  26.         {
  27.             const unsigned int shift = component * 8;
  28.             const unsigned int mask = 0xFF << shift;
  29.             return (color & mask) >> shift;            
  30.         }
  31.  
  32.         default:
  33.             throw std::invalid_argument("invalid color component");
  34.     }
  35.  
  36.     return 0;
  37. }
  38.  
  39. int main(int argc, char **argv)
  40. {
  41.     unsigned int the_color = 0xAABBCCFF;
  42.     std::cout << std::hex << "With macro:\n"
  43.         << "R: " << GET_COMPONENT(the_color, 3) << '\n'
  44.         << "G: " << GET_COMPONENT(the_color, 2) << '\n'
  45.         << "B: " << GET_COMPONENT(the_color, 1) << '\n'
  46.         << "A: " << GET_COMPONENT(the_color, 0) << '\n';
  47.  
  48.     std::cout << std::hex << "With function:\n"
  49.         << "R: " << get_component(the_color, 3) << '\n'
  50.         << "G: " << get_component(the_color, 2) << '\n'
  51.         << "B: " << get_component(the_color, 1) << '\n'
  52.         << "A: " << get_component(the_color, 0) << '\n';
  53.  
  54.     std::cout << std::hex << "With function:\n"
  55.         << "R: " << get_component(the_color, R) << '\n'
  56.         << "G: " << get_component(the_color, G) << '\n'
  57.         << "B: " << get_component(the_color, B) << '\n'
  58.         << "A: " << get_component(the_color, A) << '\n';
  59.  
  60.     return 0;
  61. }
  62.  
Success #stdin #stdout 0s 2900KB
comments (?)
stdin
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Standard input is empty
stdout
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With macro:
R: aa
G: bb
B: cc
A: ff
With function:
R: aa
G: bb
B: cc
A: ff
With function:
R: aa
G: bb
B: cc
A: ff
https://ideone.com/xvu7np
extraer RGBA con macros o funciones
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
secret

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