func dst(in []float64) []float64 {
out := make([]float64, len(in))
nr := len(in)
for i := 0; i < nr; i++ {
for j := 0; j < nr; j++ {
tmp := (float64(i) + 0.5) * (float64(j) + 0.5) / float64(nr)
out[i] += in[j] * math.Sin(tmp*math.Pi)
}
}
return out
}
func idst(in []float64) []float64 {
out := dst(in)
for i, v := range out {
out[i] = v * 2 / float64(len(in))
}
return out
}
func dct(in []float64) []float64 {
out := make([]float64, len(in))
nr := len(in)
for i := 0; i < nr; i++ {
for j := 0; j < nr; j++ {
tmp := float64(i) * (float64(j) + 0.5) / float64(nr)
out[i] += in[j] * math.Cos(tmp*math.Pi)
}
}
return out
}
func idct(in []float64) []float64 {
out := make([]float64, len(in))
nr := len(in)
for i := 0; i < nr; i++ {
out[i] = in[i] / 2
for j := 0; j < nr; j++ {
tmp := float64(j) * (float64(i) + 0.5) / float64(nr)
out[i] += in[j] * math.Cos(tmp*math.Pi)
}
out[i] = out[i] * 2 / float64(nr)
}
return out
}
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