The code

struct Color_HSV RGBtoHSV(struct Color_RGB RGB); struct Color_RGB HSVtoRGB(struct Color_HSV HSV); struct Color_RGB { double red,blue, green; //doubles used for best accuracy }; struct Color_HSV { double hue, sat, val; }; struct Color_HSV RGBtoHSV(struct Color_RGB RGB){ struct Color_HSV HSV; //structure to return double vals[3]; //thue = temporary var (linked to hue) unsigned char maxc=0, minc=0; //red=0, green=1, blue=2 vals[0]=RGB.red; vals[1]=RGB.green; vals[2]=RGB.blue; //red is set as maximum and minimum if(vals[1]>vals[maxc]) maxc=1; //if green is greater, make green the max. if(vals[2]>vals[maxc]) maxc=2; //if blue is greater, make blue the max if(vals[1]<vals[minc]) minc=1; //if green is less, make green the min. if(vals[2]<vals[minc]) minc=2; //if blue is less, make blue the min. HSV.val = vals[maxc]; //set the HSV.val to the maximum component value (this is a final value) if(vals[maxc]==0) //if maximum component is 0, color must be black HSV.sat = HSV.hue = 0; //so set values to 0 manually to avoid div by 0 errors else { //otherwise, calculate the values HSV.sat=255*(1-(vals[minc]/vals[maxc])); //compressed equation - original: HSV.sat=((vals[maxc]-vals[minc])/vals[maxc])*255; HSV.hue = 60 * ((maxc*2) + (vals[(maxc+1)%3] - vals[(maxc+2)%3])/(vals[maxc] - vals[minc])); //this cannot be simplified - and i havn't got time to explain it } if(HSV.hue < 0) HSV.hue += 360; //corrector for hues in -60 to 0 range return HSV; } struct Color_RGB HSVtoRGB(struct Color_HSV HSV) { struct Color_RGB RGB; //structure to return double min,thue,vals[3]; //thue = temporary var (linked to hue) unsigned char maxc; //red=0, green=1, blue=2 /* The biggest component (r,g or b) of the colour can be detemined * by where the hue lies. * The maximum component is eaqul to the 'value' in HSV, * so we can set the biggest component to HSV.val, * and also set the marker for which is the biggest component(maxc) * * The maximum component can be determined by where the hue lies: * it lies in one of three groups * * If the maximum component is red (0), it lies in the third of the * spectrum around red, i.e. -60 to 60 * If the maximum component is green (120), it lies in the third of the * spectrum around green, i.e. 60 to 180 * If the maximum component is blue (240), it lies in the third of the * spectrum around blue, i.e. 180 to 300 */ /* since the spectrum is circular, we can take the 300-360 section and * fit it into -60 -> 0, to fit help the group seperation */ if(HSV.hue>300) HSV.hue-=360; /* we now determine the maximum component (maxc) by the hue groups */ if(HSV.hue<60) //if it is below 60, then it is red (maxc 0) maxc=0; //The range is -60 -> 60, and there is never anything below -60 else if(HSV.hue>=180) //if it is above 180, then it is blue (maxc 2) maxc=2; //The range is 180 -> 300, and there is never anything above 300, or it would have been modified earlier else //otherwise, it must be between 60 and 180, which is green (maxc 1) maxc=1; //The range is 60 -> 180 vals[maxc]=HSV.val; //vals holds the r, g, and b values temporarialy, so set the maximum one to HSV.val (the value of the maximim component is HSV.val) /* the first of these formulae calculates the minimum * value. it has been "shrink-wrapped", so dont try to make sense of it * * I dont understand it anymore, and i'm not sure if i even did when i wrote it */ min = (HSV.val*(255-HSV.sat)) / 255; /* the second of these formulae calculates a value 'thue'. * the formaula results in a value between -1 and 1, representing * the position of the hue in it's group * this may help: (green "hue group" used as an example.) * * lwr bound ## green ## upr bound * 60 120 180 -----> Hue * |-----|-----|-----------| * hue= 90 * * lwr bound ## green ## upr bound * -1 0 1 -----> tHue * |-----|-----|-----------| * hue= -0.5 * * this part is done in the first half of the equation ((HSV.hue/60)-(2*maxc)) * * the second part multiplies it by the difference between * the maximum and minimum to get a value that is * the difference between the minimum component and the middle component. * i dont really understand why, but it works. * (HSV.val-min) */ thue=(((HSV.hue/60)-(2*maxc)) * (HSV.val-min)); if(thue>0) //if the hue is more like the color group above it, { //i.e. a green that is more 'bluey' than 'reddy' vals[(maxc+2)%3] = min; //then the minimum component is the one it is less like, the group below vals[(maxc+1)%3] = min+thue; //and the middle component is the one it is more like, the group above } else //otherwise, it must be more like the colour group below it { //i.e. a green that is more 'reddy' than 'bluey' vals[(maxc+1)%3] = min; //then the minimum component is the one it is less like, the group above vals[(maxc+2)%3] = min+thue; //and the middle component is the one it is more like, the group below } RGB.red=vals[0]; // now stuff the aray values into the return structure RGB.green=vals[1]; RGB.blue=vals[2]; return RGB; }