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Reference Guide
image2hist.C File Reference

Detailed Description

View in nbviewer Open in SWAN Create a 2-D histogram from an image.

void image2hist()
{
TASImage image("$ROOTSYS/tutorials/image/rose512.jpg");
UInt_t yPixels = image.GetHeight();
UInt_t xPixels = image.GetWidth();
UInt_t *argb = image.GetArgbArray();
TH2D* h = new TH2D("h","Rose histogram",xPixels,-1,1,yPixels,-1,1);
for (int row=0; row<xPixels; ++row) {
for (int col=0; col<yPixels; ++col) {
int index = col*xPixels+row;
float grey = float(argb[index]&0xff)/256;
h->SetBinContent(row+1,yPixels-col,grey);
}
}
h->Draw("colz");
}
Author
Olivier Couet

Definition in file image2hist.C.

gStyle
R__EXTERN TStyle * gStyle
Definition: TStyle.h:412
h
#define h(i)
Definition: RSha256.hxx:124
TH2D
2-D histogram with a double per channel (see TH1 documentation)}
Definition: TH2.h:292
TASImage
Definition: TASImage.h:31
UInt_t
unsigned int UInt_t
Definition: RtypesCore.h:46
TStyle::SetPalette
void SetPalette(Int_t ncolors=kBird, Int_t *colors=0, Float_t alpha=1.)
See TColor::SetPalette.
Definition: TStyle.cxx:1785
kCubehelix
@ kCubehelix
Definition: TColor.h:109