easings.h

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#ifndef EASINGS_H
#define EASINGS_H
 
#define EASINGS_STATIC_INLINE     // NOTE: By default, compile functions as static inline
 
#if defined(EASINGS_STATIC_INLINE)
    #define EASEDEF static inline
#else
    #define EASEDEF extern
#endif
 
#include <math.h>       // Required for: sinf(), cosf(), sqrtf(), powf()
 
#ifndef PI
    #define PI 3.14159265358979323846f //Required as PI is not always defined in math.h
#endif
 
#ifdef __cplusplus
extern "C" {            // Prevents name mangling of functions
#endif
 
// Linear Easing functions
EASEDEF float EaseLinearNone(float t, float b, float c, float d) { return (c*t/d + b); }
EASEDEF float EaseLinearIn(float t, float b, float c, float d) { return (c*t/d + b); }
EASEDEF float EaseLinearOut(float t, float b, float c, float d) { return (c*t/d + b); }
EASEDEF float EaseLinearInOut(float t,float b, float c, float d) { return (c*t/d + b); }
 
// Sine Easing functions
EASEDEF float EaseSineIn(float t, float b, float c, float d) { return (-c*cosf(t/d*(PI/2.0f)) + c + b); }
EASEDEF float EaseSineOut(float t, float b, float c, float d) { return (c*sinf(t/d*(PI/2.0f)) + b); }
EASEDEF float EaseSineInOut(float t, float b, float c, float d) { return (-c/2.0f*(cosf(PI*t/d) - 1.0f) + b); }
 
// Circular Easing functions
EASEDEF float EaseCircIn(float t, float b, float c, float d) { t /= d; return (-c*(sqrtf(1.0f - t*t) - 1.0f) + b); }
EASEDEF float EaseCircOut(float t, float b, float c, float d) { t = t/d - 1.0f; return (c*sqrtf(1.0f - t*t) + b); }
EASEDEF float EaseCircInOut(float t, float b, float c, float d)
{
    if ((t/=d/2.0f) < 1.0f) return (-c/2.0f*(sqrtf(1.0f - t*t) - 1.0f) + b);
    t -= 2.0f; return (c/2.0f*(sqrtf(1.0f - t*t) + 1.0f) + b);
}
 
// Cubic Easing functions
EASEDEF float EaseCubicIn(float t, float b, float c, float d) { t /= d; return (c*t*t*t + b); }
EASEDEF float EaseCubicOut(float t, float b, float c, float d) { t = t/d - 1.0f; return (c*(t*t*t + 1.0f) + b); }
EASEDEF float EaseCubicInOut(float t, float b, float c, float d)
{
    if ((t/=d/2.0f) < 1.0f) return (c/2.0f*t*t*t + b);
    t -= 2.0f; return (c/2.0f*(t*t*t + 2.0f) + b);
}
 
// Quadratic Easing functions
EASEDEF float EaseQuadIn(float t, float b, float c, float d) { t /= d; return (c*t*t + b); }
EASEDEF float EaseQuadOut(float t, float b, float c, float d) { t /= d; return (-c*t*(t - 2.0f) + b); }
EASEDEF float EaseQuadInOut(float t, float b, float c, float d)
{
    if ((t/=d/2) < 1) return (((c/2)*(t*t)) + b);
    return (-c/2.0f*(((t - 1.0f)*(t - 3.0f)) - 1.0f) + b);
}
 
// Exponential Easing functions
EASEDEF float EaseExpoIn(float t, float b, float c, float d) { return (t == 0.0f) ? b : (c*powf(2.0f, 10.0f*(t/d - 1.0f)) + b); }
EASEDEF float EaseExpoOut(float t, float b, float c, float d) { return (t == d) ? (b + c) : (c*(-powf(2.0f, -10.0f*t/d) + 1.0f) + b);    }
EASEDEF float EaseExpoInOut(float t, float b, float c, float d)
{
    if (t == 0.0f) return b;
    if (t == d) return (b + c);
    if ((t/=d/2.0f) < 1.0f) return (c/2.0f*powf(2.0f, 10.0f*(t - 1.0f)) + b);
 
    return (c/2.0f*(-powf(2.0f, -10.0f*(t - 1.0f)) + 2.0f) + b);
}
 
// Back Easing functions
EASEDEF float EaseBackIn(float t, float b, float c, float d)
{
    float s = 1.70158f;
    float postFix = t/=d;
    return (c*(postFix)*t*((s + 1.0f)*t - s) + b);
}
 
EASEDEF float EaseBackOut(float t, float b, float c, float d)
{
    float s = 1.70158f;
    t = t/d - 1.0f;
    return (c*(t*t*((s + 1.0f)*t + s) + 1.0f) + b);
}
 
EASEDEF float EaseBackInOut(float t, float b, float c, float d)
{
    float s = 1.70158f;
    if ((t/=d/2.0f) < 1.0f)
    {
        s *= 1.525f;
        return (c/2.0f*(t*t*((s + 1.0f)*t - s)) + b);
    }
 
    float postFix = t-=2.0f;
    s *= 1.525f;
    return (c/2.0f*((postFix)*t*((s + 1.0f)*t + s) + 2.0f) + b);
}
 
// Bounce Easing functions
EASEDEF float EaseBounceOut(float t, float b, float c, float d)
{
    if ((t/=d) < (1.0f/2.75f))
    {
        return (c*(7.5625f*t*t) + b);
    }
    else if (t < (2.0f/2.75f))
    {
        float postFix = t-=(1.5f/2.75f);
        return (c*(7.5625f*(postFix)*t + 0.75f) + b);
    }
    else if (t < (2.5/2.75))
    {
        float postFix = t-=(2.25f/2.75f);
        return (c*(7.5625f*(postFix)*t + 0.9375f) + b);
    }
    else
    {
        float postFix = t-=(2.625f/2.75f);
        return (c*(7.5625f*(postFix)*t + 0.984375f) + b);
    }
}
 
EASEDEF float EaseBounceIn(float t, float b, float c, float d) { return (c - EaseBounceOut(d - t, 0.0f, c, d) + b); }
EASEDEF float EaseBounceInOut(float t, float b, float c, float d)
{
    if (t < d/2.0f) return (EaseBounceIn(t*2.0f, 0.0f, c, d)*0.5f + b);
    else return (EaseBounceOut(t*2.0f - d, 0.0f, c, d)*0.5f + c*0.5f + b);
}
 
// Elastic Easing functions
EASEDEF float EaseElasticIn(float t, float b, float c, float d)
{
    if (t == 0.0f) return b;
    if ((t/=d) == 1.0f) return (b + c);
 
    float p = d*0.3f;
    float a = c;
    float s = p/4.0f;
    float postFix = a*powf(2.0f, 10.0f*(t-=1.0f));
 
    return (-(postFix*sinf((t*d-s)*(2.0f*PI)/p )) + b);
}
 
EASEDEF float EaseElasticOut(float t, float b, float c, float d)
{
    if (t == 0.0f) return b;
    if ((t/=d) == 1.0f) return (b + c);
 
    float p = d*0.3f;
    float a = c;
    float s = p/4.0f;
 
    return (a*powf(2.0f,-10.0f*t)*sinf((t*d-s)*(2.0f*PI)/p) + c + b);
}
 
EASEDEF float EaseElasticInOut(float t, float b, float c, float d)
{
    if (t == 0.0f) return b;
    if ((t/=d/2.0f) == 2.0f) return (b + c);
 
    float p = d*(0.3f*1.5f);
    float a = c;
    float s = p/4.0f;
 
    if (t < 1.0f)
    {
        float postFix = a*powf(2.0f, 10.0f*(t-=1.0f));
        return -0.5f*(postFix*sinf((t*d-s)*(2.0f*PI)/p)) + b;
    }
 
    float postFix = a*powf(2.0f, -10.0f*(t-=1.0f));
 
    return (postFix*sinf((t*d-s)*(2.0f*PI)/p)*0.5f + c + b);
}
 
#ifdef __cplusplus
}
#endif
 
#endif // EASINGS_H