/** getIndexNearXY: return index of point within (or closest too)
x +- dx which is closest to y **/
int Curve::getIndexNearXY(double x, double dx_per_pix, double y) const {
VectorPtr xv = *_inputVectors.find(XVECTOR);
VectorPtr yv = *_inputVectors.find(YVECTOR);
if (!xv || !yv) {
return 0; // anything better we can do?
}
double xi, yi, dx, dxi, dy, dyi;
bool first = true;
int i,i0, iN, index;
int sc = sampleCount();
if (xv->isRising()) {
iN = i0 = indexNearX(x, xv, NS);
xi = xv->interpolate(i0, NS);
while (i0 > 0 && x-dx_per_pix < xi) {
xi = xv->interpolate(--i0, NS);
}
xi = xv->interpolate(iN, NS);
while (iN < sc-1 && x+dx_per_pix > xi) {
xi = xv->interpolate(++iN, NS);
}
} else {
i0 = 0;
iN = sampleCount()-1;
}
index = i0;
xi = xv->interpolate(index, NS);
yi = yv->interpolate(index, NS);
dx = fabs(x - xi);
dy = fabs(y - yi);
for (i = i0 + 1; i <= iN; i++) {
xi = xv->interpolate(i, NS);
dxi = fabs(x - xi);
if (dxi < dx_per_pix) {
dx = dxi;
yi = yv->interpolate(i, NS);
dyi = fabs(y - yi);
if (first || dyi < dy) {
first = false;
index = i;
dy = dyi;
}
} else if (dxi < dx) {
dx = dxi;
index = i;
}
}
return index;
}
inline int indexNearX(double x, VectorPtr& xv, int NS) {
// monotonically rising: we can do a binary search
// should be reasonably fast
if (xv->isRising()) {
int i_top = NS - 1;
int i_bot = 0;
// don't pre-check for x outside of the curve since this is not
// the common case. It will be correct - just slightly slower...
while (i_bot + 1 < i_top) {
int i0 = (i_top + i_bot)/2;
double rX = xv->interpolate(i0, NS);
if (x < rX) {
i_top = i0;
} else {
i_bot = i0;
}
}
double xt = xv->interpolate(i_top, NS);
double xb = xv->interpolate(i_bot, NS);
if (xt - x < x - xb) {
return i_top;
} else {
return i_bot;
}
} else {
// Oh Oh... not monotonically rising - we have to search the entire curve!
// May be unbearably slow for large vectors
double rX = xv->interpolate(0, NS);
double dx0 = fabs(x - rX);
int i0 = 0;
for (int i = 1; i < NS; ++i) {
rX = xv->interpolate(i, NS);
double dx = fabs(x - rX);
if (dx < dx0) {
dx0 = dx;
i0 = i;
}
}
return i0;
}
}
