# C Program to Change RGB color model to HSV color model

CServer Side ProgrammingProgramming

#### C in Depth: The Complete C Programming Guide for Beginners

45 Lectures 4.5 hours

#### Practical C++: Learn C++ Basics Step by Step

Most Popular

50 Lectures 4.5 hours

#### Master C and Embedded C Programming- Learn as you go

66 Lectures 5.5 hours

Given RGB color range in form of integers; the task is to find its appropriate HSV color by converting the RGB color range

## What is RGB color model

RGB color model comprised of three colors Red, Green and Blue. RGB model is a color model which is widely used in the display technologies; it is an additive model in which we add these three colors of with different intensities to produce millions of different colors on a display device.

## What is HSV color model?

HSV color model comprises Hue, Saturation, Value also known as HSB (Hue, Saturation, Brightness).HSV is alternative representation of RGB color model. It is aligned in a way how human vision perceives color making attributes. This color model more often used by artists due to it’s natural color scheme. The three attributes of the HSV can be additive as well as subtractive.

## What we have to do in the program

We have to take input from the user of RGB model values and then mathematically calculate the output in HSV color model.

## Example

Input: r = 31, g = 52, b = 29
Output: h s v = (114.782608, 44.230770, 20.392157)
Input: r = 129, g = 88, b = 47
Output: h s v=(30.000000, 63.565895, 50.588238)

Approach we will be using to solve the given problem −

• Taking the input in 3 colors Red(r), Green(g) and Blue(b).
• Dividing all the color values with 255.
• Now calculate cmax, cmin and difference.
• Check −
• If cmax and cmin equal to 0, then Hue or h will be 0.
• If cmax equal to Red(r) then Hue(h) = (60 * ((g – b) / diff) + 360) % 360.
• If cmax equal to Green(g) then Hue(h) = (60 * ((b – r) / diff) + 120) % 360.
• If cmax equal to Blue(b) then Hue(h) = (60 * ((r – g) / diff) + 240) % 360.
• To find saturation we will check −
• If cmax = 0 then Saturation (s) = 0.
• If cmax does not equal to zero then Saturation (s) = (diff/cmax)*100
• Value computation −
• Value (v) = cmax *100

## Algorithm

Start
Step 1 -> In function float max(float a, float b, float c)
Return (a > b)? (a > c ? a : c) : (b > c ? b : c)
Step 2 -> In function float min(float a, float b, float c)
Return (a < b)? (a < c ? a : c) : (b < c ? b : c)
Step 3 -> In function int rgb_to_hsv(float r, float g, float b)
Declare float h, s, v
Set r = r / 255.0
Set g = g / 255.0
Set b = b / 255.0
Set cmax = max(r, g, b)
Set cmin = min(r, g, b)
Set diff = cmax-cmin
If cmax == cmin then,
Set h = 0
End if
Else if cmax == r then,
Set h = fmod((60 * ((g - b) / diff) + 360), 360.0)
End Else if
Else if cmax == g then,
Set h = fmod((60 * ((b - r) / diff) + 120), 360.0)
End Else if
Else if cmax == b then,
Set h = fmod((60 * ((r - g) / diff) + 240), 360.0)
End Else if
If cmax == 0 then,
Set s = 0
End if
Else
Set s = (diff / cmax) * 100
End Else
v = cmax * 100;
Print h, s, v
Step 4 -> int main(int argc, char const *argv[])
Declare and initialize r = 45, g = 215, b = 0
Call function rgb_to_hsv(r, g, b)
Stop

## Example

#include <stdio.h>
#include <math.h>
float max(float a, float b, float c) {
return ((a > b)? (a > c ? a : c) : (b > c ? b : c));
}
float min(float a, float b, float c) {
return ((a < b)? (a < c ? a : c) : (b < c ? b : c));
}
int rgb_to_hsv(float r, float g, float b) {
// R, G, B values are divided by 255
// to change the range from 0..255 to 0..1:
float h, s, v;
r /= 255.0;
g /= 255.0;
b /= 255.0;
float cmax = max(r, g, b); // maximum of r, g, b
float cmin = min(r, g, b); // minimum of r, g, b
float diff = cmax-cmin; // diff of cmax and cmin.
if (cmax == cmin)
h = 0;
else if (cmax == r)
h = fmod((60 * ((g - b) / diff) + 360), 360.0);
else if (cmax == g)
h = fmod((60 * ((b - r) / diff) + 120), 360.0);
else if (cmax == b)
h = fmod((60 * ((r - g) / diff) + 240), 360.0);
// if cmax equal zero
if (cmax == 0)
s = 0;
else
s = (diff / cmax) * 100;
// compute v
v = cmax * 100;
printf("h s v=(%f, %f, %f)\n", h, s, v );
return 0;
}
//main function
int main(int argc, char const *argv[]) {
int r = 45, g = 215, b = 0;
rgb_to_hsv(r, g, b);
return 0;
}

## Output

h s v=(107.441864, 100.000000, 84.313728)
Updated on 20-Nov-2019 10:52:39