A “Perceptual” colormap explicitly identifies a fixed value in the data
On geographical plot this fixed point can, for instance, the "sea level". A perceptual colormap provides a monotonic luminance variations above and below this fixed value. Unlike the rainbow colormap, this colormap provides a faithful representation of the structures in the data.
This macro demonstrates how to produce the perceptual colormap shown on the figure 2 in this article.
The function Perceptual_Colormap
takes two parameters as input:
h
, the TH2D
to be drawn
val_cut
, the Z value defining the "sea level"
Having these parameters this function defines two color maps: one above val_cut
and one below.
Double_t per_cut = (val_cut-min)/(max-min);
Double_t Red[Number] = { 0.11, 0.19 , 0.30, 0.89};
Double_t Green[Number] = { 0.03, 0.304, 0.60, 0.91};
Double_t Blue[Number] = { 0.18, 0.827, 0.50, 0.70};
Double_t Stops[Number] = { 0., per_cut, per_cut+eps, 1. };
}
void perceptualcolormap() {
TH2D *
h =
new TH2D(
"h",
"Perceptual Colormap",200,-4,4,200,-4,4);
for (
Int_t i=0;i<1000000;i++) {
h->Fill(
a-1.5,
b-1.5,0.1);
h->Fill(
a+1.5,
b+1.5,-0.08);
}
Perceptual_Colormap(
h, 0.);
}
R__EXTERN TRandom * gRandom
static Int_t CreateGradientColorTable(UInt_t Number, Double_t *Stops, Double_t *Red, Double_t *Green, Double_t *Blue, UInt_t NColors, Float_t alpha=1., Bool_t setPalette=kTRUE)
Static function creating a color table with several connected linear gradients.
2-D histogram with a double per channel (see TH1 documentation)}
virtual void Rannor(Float_t &a, Float_t &b)
Return 2 numbers distributed following a gaussian with mean=0 and sigma=1.
- Author
- Olivier Couet
Definition in file perceptualcolormap.C.