Logo ROOT   6.18/05
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.
TEllipse *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();
}
double Double_t
Definition: RtypesCore.h:55
Draw all kinds of Arrows.
Definition: TArrow.h:29
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
virtual void SetFillColorAlpha(Color_t fcolor, Float_t falpha)
Set a transparent fill color.
Definition: TAttFill.cxx:260
virtual void SetLineWidth(Width_t lwidth)
Set the line width.
Definition: TAttLine.h:43
virtual void SetLineColorAlpha(Color_t lcolor, Float_t lalpha)
Set a transparent line color.
Definition: TAttLine.cxx:291
virtual void SetLineColor(Color_t lcolor)
Set the line color.
Definition: TAttLine.h:40
The Canvas class.
Definition: TCanvas.h:31
Draw Ellipses.
Definition: TEllipse.h:24
virtual void Draw(Option_t *option="")
Draw this ellipse with its current attributes.
Definition: TEllipse.cxx:166
A Graph is a graphics object made of two arrays X and Y with npoints each.
Definition: TGraph.h:41
To draw Mathematical Formula.
Definition: TLatex.h:18
Manages Markers.
Definition: TMarker.h:23
return c1
Definition: legend1.C:41
Double_t y[n]
Definition: legend1.C:17
Double_t x[n]
Definition: legend1.C:17
Definition: graph.py:1
Author
Olivier Couet

Definition in file transparency.C.