AndreAhmed AndreAhmed - 1 month ago 20
C++ Question

Converting float RGBA to int RGB

I have a float RGBA which is from 0 to 1. I would like to convert it to int rgb

class Color
{
public:
float R, G, B, A;

Color(float r = 1.0f, float g = 1.0f, float b = 1.0f, float a = 1.0f);
}

Answer

[Edited] due to later "I want to convert the 32bit RGBA to 8bit R2G4B2"

[Edited again] due to "I'm using it on Embedded system, so static cast is not allowed"

[edited even more] due to "I'm using a c99 compiler" - so no C++

struct Color
{
        float R, G, B, A;
}

int RGBAstructTo8bitRGB(const Color* color) {
    if(NULL==color) { return 0; /* black */
    unsigned r=(int)(3*(color->R < 0 ? 0 : this->R));
    unsigned g=(int)(7*(color->G < 0 ? 0 : this->G));
    unsigned b=(int)(3*(color->B < 0 ? 0 : this->B));
    return (r<<6) | (g<<2) | b;
}
int RGBATo8bitRGB(float R, float G, float B) {
    unsigned r=(int)(3*(R < 0 ? 0 : this->R));
    unsigned g=(int)(7*(G < 0 ? 0 : this->G));
    unsigned b=(int)(3*(B < 0 ? 0 : this->B));
    return (r<<6) | (g<<2) | b;
}

void 8bitRGBtoRGBAstruct(int color, struct Color* dest) {
  if(NULL!=dest) {
    dest->R=(float)((color & 0x03)/3.0);
    dest->G=(float)(((color >> 2) & 0x07)/7.0);
    dest->B=(float)(((color >> 6) & 0x03)/3.0);
  }
} 

For a 24-bit RGB:

Ignore A, scale the components to [0,255], shift-or them into an int:

class Color
{
    public:
        float R, G, B, A;

        int toRGB() const {
          unsigned r=(int)(255*(this->R < 0 ? 0 : this->R));
          unsigned g=(int)(255*(this->G < 0 ? 0 : this->G));
          unsigned b=(int)(255*(this->B < 0 ? 0 : this->B));
          return (r<<16) | (g<<8) | b;
        }
}