#include "pixel.h"
#include <assert.h>
#include <math.h>
#include <stdlib.h>



/**
 * Component
 **/
Component ComponentRandom(void)
{
    return rand() % 256;
}


Component ComponentScale(Component c, double f)
{
    return ComponentClamp((int) floor(c * f + 0.5));
}


Component ComponentLerp(Component c, Component d, double t)
{
    return ComponentClamp((int) floor((1.0 - t) * c + t * d + 0.5));
}



/**
 * Pixel
 **/
Component Pixel::Luminance ()
{
    return (r * 76 + g * 150 + b * 29) >> 8;
}

void Pixel::SetClamp (double r_, double g_, double b_)
{
    r = ComponentClamp((int)r_);
    g = ComponentClamp((int)g_);
    b = ComponentClamp((int)b_);
}

void Pixel::SetClamp (double r_, double g_, double b_, double a_)
{
    r = ComponentClamp((int)r_);
    g = ComponentClamp((int)g_);
    b = ComponentClamp((int)b_);
    a = ComponentClamp((int)a_);
}

Pixel PixelRandom(void)
{
    return Pixel(
        ComponentRandom(),
        ComponentRandom(),
        ComponentRandom(),
        ComponentRandom());
}


Pixel operator+ (const Pixel& p, const Pixel& q)
{
    return Pixel(
        ComponentClamp(p.r + q.r),
        ComponentClamp(p.g + q.g),
        ComponentClamp(p.b + q.b),
        ComponentClamp(p.a + q.a));
}


Pixel operator* (const Pixel& p, const Pixel& q)
{
    return Pixel(
        ComponentClamp(p.r * q.r),
        ComponentClamp(p.g * q.g),
        ComponentClamp(p.b * q.b),
        ComponentClamp(p.a * q.a));
}


Pixel operator* (const Pixel& p, double f)
{
    return Pixel(
        ComponentScale(p.r, f),
        ComponentScale(p.g, f),
        ComponentScale(p.b, f),
        ComponentScale(p.a, f));
}


Pixel PixelLerp (const Pixel& p, const Pixel& q, double t)
{
    return Pixel(
        ComponentLerp(p.r, q.r, t),
        ComponentLerp(p.g, q.g, t),
        ComponentLerp(p.b, q.b, t),
        ComponentLerp(p.a, q.a, t));
}



Pixel PixelOver (const Pixel& bottom, const Pixel& top)
{
    double alpha = bottom.a / 255.0;
    double beta = top.a / 255.0;

    return top*beta + bottom*((1.0-beta)*alpha);
}



