colors.hpp

// Homepage: https://github.com/ananthvk/cpp-raytracer
// A header file for managing color related functions
#pragma once
#include "commons.hpp"

// Use vec3 instead of creating a custom struct to simplify the implementation
// and to avoid defining custom operator overloads
using color = vec3;

/// @brief Converts RGB(int, [0,255]) to RGB(float, [0.0, 1.0])
/// @param r Red
/// @param g Green
/// @param b Blue
/// @return Color as represented in floating point notation
static color color_from_rgb(int r, int g, int b)
{
    return color((double)r / 255, (double)g / 255, (double)b / 255);
}

/// @brief Perform linear interpolation.
/// @param s Start color
/// @param e End color
/// @param t parameter
/// @return The interpolated value between the two colors
inline color lerp(color s, color e, float t)
{
    return color(lerp(s.x, e.x, t), lerp(s.y, e.y, t), lerp(s.z, e.z, t));
}

// Some commonly used colors
// ===========================
const color SKY_COLOR = color_from_rgb(135, 206, 235);
const color SKY_COLOR_2 = color(0.5, 0.7, 1.0);
const color WHITE = color_from_rgb(255, 255, 255);
const color LIGHT_SKY = color_from_rgb(188, 227, 244);
const color RED = color(1, 0, 0);
const color GREEN = color(0, 1, 0);
const color BLUE = color(0, 0, 1);
const color BLACK = color(0, 0, 0);

/// @brief Applies gamma correction to each individual channel of the color as x^(1/power)
/// @param color Input color
/// @param power Gamma factor
/// @return Gamma corrected color
inline color gamma_correction(color color, int power)
{
    if (power == 1)
    {
        // no gamma correction
    }
    else if (power == 2)
    {
        // gamma 2 - use sqrt
        color.x = std::sqrt(color.x);
        color.y = std::sqrt(color.y);
        color.z = std::sqrt(color.z);
    }
    else if (power == 3)
    {
        // gamma 3 - use cbrt
        color.x = std::cbrt(color.x);
        color.y = std::cbrt(color.y);
        color.z = std::cbrt(color.z);
    }
    else
    {
        // gamma n
        color.x = std::pow(color.x, 1.0 / power);
        color.y = std::pow(color.y, 1.0 / power);
        color.z = std::pow(color.z, 1.0 / power);
    }
    return color;
}