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image2hist.C
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1/// \file
2/// \ingroup tutorial_image
3/// \notebook
4/// Create a 2-D histogram from an image.
5///
6/// \macro_image
7/// \macro_code
8///
9/// \author Olivier Couet
10
11void image2hist()
12{
13 TASImage image("$ROOTSYS/tutorials/image/rose512.jpg");
14 UInt_t yPixels = image.GetHeight();
15 UInt_t xPixels = image.GetWidth();
16 UInt_t *argb = image.GetArgbArray();
17
18 TH2D* h = new TH2D("h","Rose histogram",xPixels,-1,1,yPixels,-1,1);
19
20 for (int row=0; row<xPixels; ++row) {
21 for (int col=0; col<yPixels; ++col) {
22 int index = col*xPixels+row;
23 float grey = float(argb[index]&0xff)/256;
24 h->SetBinContent(row+1,yPixels-col,grey);
25 }
26 }
27
29 h->Draw("colz");
30}
#define h(i)
Definition RSha256.hxx:106
unsigned int UInt_t
Definition RtypesCore.h:46
@ kCubehelix
Definition TColor.h:109
R__EXTERN TStyle * gStyle
Definition TStyle.h:412
Image class.
Definition TASImage.h:31
2-D histogram with a double per channel (see TH1 documentation)}
Definition TH2.h:292
void SetPalette(Int_t ncolors=kBird, Int_t *colors=0, Float_t alpha=1.)
See TColor::SetPalette.
Definition TStyle.cxx:1782