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grad2.C
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1/// \file
2/// \ingroup tutorial_gl
3/// Gradient fill with transparency and the "SAME" option.
4/// To use this macro you need OpenGL enabled in pad:
5/// either set OpenGL.CanvasPreferGL to 1 in $ROOTSYS/etc/system.rootrc;
6/// or call `gStyle->SetCanvasPreferGL(kTRUE);` before canvas created.
7///
8/// \macro_image(nobatch)
9/// \macro_code
10///
11/// \author Timur Pocheptsov
12
13//Includes for ACLiC (cling does not need them).
14#include "TColorGradient.h"
15#include "TCanvas.h"
16#include "TError.h"
17#include "TColor.h"
18#include "TStyle.h"
19#include "TH1F.h"
20
21//Aux. functions for tutorials/gl.
22#include "customcolorgl.h"
23
24void grad2()
25{
26 //1. 'Allocate' four indices for our custom colors.
27 //We can use hard-coded indices like 1001, 1002, 1003 ... but
28 //I prefer to find free indices in the ROOT's color table
29 //to avoid possible conflicts with other tutorials.
30 Color_t freeIndices[4] = {};
32 ::Error("grad2", "can not allocate new custom colors");
33 return;
34 }
35
36 //'Aliases' (instead of freeIndices[someIndex])
37 const Color_t customRed = freeIndices[0], grad1 = freeIndices[1];
38 const Color_t customGreen = freeIndices[2], grad2 = freeIndices[3];
39
40 //Make sure canvas supports OpenGL.
42
43 //2. Check that we have a canvas with an OpenGL support.
44 TCanvas * const cnv = new TCanvas("gradiend demo 2", "gradient demo 2", 100, 100, 800, 600);
45 if (!cnv->UseGL()) {
46 ::Error("grad2", "This macro requires OpenGL");
47 delete cnv;
48 return;
49 }
50
51 //3. Custom colors:
52 // a) Custom semi-transparent red.
53 new TColor(customRed, 1., 0., 0., "red", 0.5);
54
55
56
57 // b) Gradient (from our semi-transparent red to ROOT's kOrange).
58 // Linear gradient is defined by: 1) colors (to interpolate between them),
59 // 2) coordinates for these colors along the gradient axis [0., 1.] (must be sorted!).
60 // 3) Start and end points for a gradient, you specify them in some NDC rect ([0,0 - 1,1]),
61 // and this rect is either: bounding rect of your polygon/object to fill
62 // (gradient->SetCoordinateMode(TColorGradient::kObjectBoundingMode))
63 // or bounding rect of a pad (gradient->SetCoordinateMode(TColorGradient::kPadMode)).
64 // kObjectBoundingMode is the default one.
65
66 const Double_t locations[] = {0., 1.};
67 const Color_t idx1[] = {customRed, kOrange};
68 TLinearGradient * const gradFill1 = new TLinearGradient(grad1, 2, locations, idx1);
69
70 typedef TColorGradient::Point Point;
71 //Starting and ending points for a gradient fill (it's a vertical gradient):
72 gradFill1->SetStartEnd(Point(0., 0.), Point(0., 1.));
73
74 // c) Custom semi-transparent green.
75 new TColor(customGreen, 0., 1., 0., "green", 0.5);
76
77 // d) Gradient from ROOT's kBlue to our custom green.
78 const Color_t idx2[] = {customGreen, kBlue};
79
80 TLinearGradient * const gradFill2 = new TLinearGradient(grad2, 2, locations, idx2);
81 //Vertical gradient fill.
82 gradFill2->SetStartEnd(Point(0., 0.), Point(0., 1.));
83
84 TH1F * const hist = new TH1F("a2", "b2", 10, -2., 3.);
85 TH1F * const hist2 = new TH1F("c3", "d3", 10, -3., 3.);
86 hist->FillRandom("landau", 100000);
87 hist2->FillRandom("gaus", 100000);
88
89 hist->SetFillColor(grad1);
90 hist2->SetFillColor(grad2);
91
92 hist2->Draw();
93 hist->Draw("SAME");
94}
short Color_t
Definition: RtypesCore.h:92
double Double_t
Definition: RtypesCore.h:59
const Bool_t kTRUE
Definition: RtypesCore.h:100
@ kOrange
Definition: Rtypes.h:67
@ kBlue
Definition: Rtypes.h:66
void Error(const char *location, const char *msgfmt,...)
Use this function in case an error occurred.
Definition: TError.cxx:187
R__EXTERN TStyle * gStyle
Definition: TStyle.h:414
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
The Canvas class.
Definition: TCanvas.h:23
Bool_t UseGL() const
Definition: TCanvas.h:223
The color creation and management class.
Definition: TColor.h:19
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:574
virtual void FillRandom(const char *fname, Int_t ntimes=5000, TRandom *rng=nullptr)
Fill histogram following distribution in function fname.
Definition: TH1.cxx:3513
void Draw(Option_t *option="") override
Draw this histogram with options.
Definition: TH1.cxx:3060
Define a linear color gradient.
void SetStartEnd(const Point &p1, const Point &p2)
Set end and start.
void SetCanvasPreferGL(Bool_t prefer=kTRUE)
Definition: TStyle.h:326
unsigned FindFreeCustomColorIndices(T(&indices)[N])
Definition: customcolorgl.h:40