class TAttMarker

Marker Attributes class

This class is used (in general by secondary inheritance) by many other classes (graphics, histograms). It holds all the markers attributes.

Marker attributes

The marker attributes are:

• Marker color.
• Marker style.
• Marker size.

Marker color

The marker color is a color index (integer) pointing in the ROOT color table. The marker color of any class inheriting from TAttMarker can be changed using the method SetMarkerColor and retrieved using the method GetMarkerColor. The following table shows the first 50 default colors.

Color transparency

SetMarkerColorAlpha(), allows to set a transparent color. In the following example the marker color of the histogram histo is set to blue with a transparency of 35%. The color kBlue itself remains fully opaque.

histo->SetMarkerColorAlpha(kBlue, 0.35);

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

Marker style

The Marker style defines the markers' shape. The marker style of any class inheriting from TAttMarker can be changed using the method SetMarkerStyle and retrieved using the method GetMarkerStyle. The following list gives the currently supported markers (screen and PostScript) style. Each marker style is identified by an integer number (first column) corresponding to a marker shape (second column) and can be also accessed via a global name (third column).

   Marker number         Marker shape          Marker name
        1                    dot                  kDot
        2                    +                    kPlus
        3                    *                    kStar
        4                    o                    kCircle
        5                    x                    kMultiply
        6                    small dot            kFullDotSmall
        7                    medium dot           kFullDotMedium
        8                    large scalable dot   kFullDotLarge
        9 -->19              large scalable dot
       20                    full circle          kFullCircle
       21                    full square          kFullSquare
       22                    full triangle up     kFullTriangleUp
       23                    full triangle down   kFullTriangleDown
       24                    open circle          kOpenCircle
       25                    open square          kOpenSquare
       26                    open triangle up     kOpenTriangleUp
       27                    open diamond         kOpenDiamond
       28                    open cross           kOpenCross
       29                    full star            kFullStar
       30                    open star            kOpenStar
       31                    *
       32                    open triangle down
       33                    full diamond
       34                    full cross

Marker size

Various marker sizes are shown in the figure below. The default marker size=1 is shown in the top left corner. Marker sizes smaller than 1 can be specified. The marker size does not refer to any coordinate systems, it is an absolute value. Therefore the marker size is not affected by any change in TPad's scale. A marker size equl to 1 correspond to 8 pixels. That is, a square marker with size 1 will be drawn with a side equal to 8 pixels on the screen. The marker size of any class inheriting from TAttMarker can be changed using the method SetMarkerSize and retrieved using the method GetMarkerSize.

Note that the marker styles number 1 6 and 7 (the dots), cannot be scaled. They are meant to be very fast to draw and are always drawn with the same number of pixels; therefore SetMarkerSize does not apply on them. To have a "scalable dot" a filled circle should be used instead, i.e. the marker style number 20. By default (if SetMarkerStyle is not specified), the marker style used is 1. That's the most common one to draw scatter plots.