EOT Bgcolor

//By Glaz and LazyBear
study(title="Ehlers Early Onset Trend",shorttitle="EOT")
Period=input(20)
Q1=input(0.8)
Q2=input(0.4)

Quotient(LPPeriod, K)=>
    PI = 3.1415926
    angle = 0.707 * 2 * PI / 100
    alpha1 = ( cos( angle ) + sin( angle ) - 1 ) / cos( angle )

    a1 = exp( -1.414 * PI / LPPeriod )
    b1 = 2 * a1 * cos( 1.414 * PI / LPPeriod )
    c2 = b1
    c3 = -a1 * a1
    c1 = 1 - c2 - c3

    HP= pow((1-alpha1/2),2)*(close - (2*close[1]) + close[2]) + 2*(1-alpha1)*nz(HP[1]) - pow((1-alpha1),2)* nz(HP[2])
    Filt= c1 * (HP + nz(HP[1]))/2 + c2*nz(Filt[1]) + c3*nz(Filt[2])
    Pk= iff(abs(Filt) >  0.991 *nz(Pk[1]), abs(Filt), 0.991 * nz(Pk[1]))
    X = nz(Filt / Pk)

    q=( X + K ) / ( K * X + 1 )

plot(Quotient( Period, Q1 ),color=red)
plot(Quotient( Period, Q2 ),color=aqua)
hline(0)

red1 = Quotient(Period,Q1)
aqua1 = Quotient(Period,Q2)

up = crossover(red1,0)
down = crossunder(aqua1,0)

bgcolor(down?red:na,transp=50)
bgcolor(up?green:na,transp=50)