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Reference Guide
transparency.C File Reference

Detailed Description

View in nbviewer Open in SWAN This macro demonstrates the use of color transparency.

It is done by specifying the alpha value of a given color. For instance

ellipse->SetFillColorAlpha(9, 0.571);

changes the ellipse fill color to the index 9 with an alpha value of 0.571. 0. would be fully transparent (invisible) and 1. completely opaque (the default).

The transparency is available on all platforms when the flag OpenGL.CanvasPreferGL is set to 1 in $ROOTSYS/etc/system.rootrc, or on Mac with the Cocoa backend. X11 does not support transparency. On the file output it is visible with PDF, PNG, Gif, JPEG, SVG, TeX ... but not PostScript.

void transparency()
{
auto c1 = new TCanvas("c1", "c1",224,330,700,527);
c1->Range(-0.125,-0.125,1.125,1.125);
auto tex = new TLatex(0.06303724,0.0194223,"This text is opaque and this line is transparent");
tex->SetLineWidth(2);
tex->Draw();
auto arrow = new TArrow(0.5555158,0.07171314,0.8939828,0.6195219,0.05,"|>");
arrow->SetLineWidth(4);
arrow->SetAngle(30);
arrow->Draw();
// Draw a transparent graph.
Double_t x[10] = {
0.5232808, 0.8724928, 0.9280086, 0.7059456, 0.7399714,
0.4659742, 0.8241404, 0.4838825, 0.7936963, 0.743553};
Double_t y[10] = {
0.7290837, 0.9631474, 0.4775896, 0.6494024, 0.3555777,
0.622012, 0.7938247, 0.9482072, 0.3904382, 0.2410359};
auto graph = new TGraph(10,x,y);
graph->SetLineColorAlpha(46, 0.1);
graph->SetLineWidth(7);
graph->Draw("l");
// Draw an ellipse with opaque colors.
auto ellipse = new TEllipse(0.1740688,0.8352632,0.1518625,0.1010526,0,360,0);
ellipse->SetFillColor(30);
ellipse->SetLineColor(51);
ellipse->SetLineWidth(3);
ellipse->Draw();
// Draw an ellipse with transparent colors, above the previous one.
ellipse = new TEllipse(0.2985315,0.7092105,0.1566977,0.1868421,0,360,0);
ellipse->SetFillColorAlpha(9, 0.571);
ellipse->SetLineColorAlpha(8, 0.464);
ellipse->SetLineWidth(3);
ellipse->Draw();
// Draw a transparent blue text.
tex = new TLatex(0.04871059,0.1837649,"This text is transparent");
tex->SetTextColorAlpha(9, 0.476);
tex->SetTextSize(0.125);
tex->SetTextAngle(26.0);
tex->Draw();
// Draw two transparent markers
auto marker = new TMarker(0.03080229,0.998008,20);
marker->SetMarkerColorAlpha(2, .3);
marker->SetMarkerStyle(20);
marker->SetMarkerSize(1.7);
marker->Draw();
marker = new TMarker(0.1239255,0.8635458,20);
marker->SetMarkerColorAlpha(2, .2);
marker->SetMarkerStyle(20);
marker->SetMarkerSize(1.7);
marker->Draw();
// Draw an opaque marker
marker = new TMarker(0.3047994,0.6344622,20);
marker->SetMarkerColor(2);
marker->SetMarkerStyle(20);
marker->SetMarkerSize(1.7);
marker->Draw();
}
Author
Olivier Couet

Definition in file transparency.C.

TEllipse
Definition: TEllipse.h:23
x
Double_t x[n]
Definition: legend1.C:17
TLatex
Definition: TLatex.h:18
y
Double_t y[n]
Definition: legend1.C:17
TObject::Draw
virtual void Draw(Option_t *option="")
Default Draw method for all objects.
Definition: TObject.cxx:197
Double_t
double Double_t
Definition: RtypesCore.h:59
TGraph
Definition: TGraph.h:41
TCanvas
Definition: TCanvas.h:23
arrow
Definition: RArrowDS.hxx:9
graph
Definition: graph.py:1
TArrow
Definition: TArrow.h:29
TAttText::SetTextColorAlpha
virtual void SetTextColorAlpha(Color_t tcolor, Float_t talpha)
Set a transparent marker color.
Definition: TAttText.cxx:382
TMarker
Definition: TMarker.h:22
c1
return c1
Definition: legend1.C:41