adding new tutorial

Author: xination

color_demos/_01_customized_color.C

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+
+// This script demo how to set customize color
+// color picker
+// https://www.w3schools.com/colors/colors_picker.asp 
+void _01_customized_color() {
+
+
+    int rgb [] = { 102, 255, 225 }; // light blue
+    // normally, each r, g, b ranges from 0 to 255,
+    // but in ROOT, each r, g, b range from 0 to 1.
+    // so you have to divide them by 255.
+
+    // to use a customize color,
+    // we have to find a "free" color index to register the new color 
+    // it can be done by TColor::GetFreeColorIndex()
+    // then construct the color.
+    
+    int myColor_idx = TColor::GetFreeColorIndex(); // get the free index.
+
+    TColor* myColor = new TColor( myColor_idx, rgb[0]/255., rgb[1]/255., rgb[2]/255.  ); 
+    // use free index, and rgb values to instantiate TColor object.
+
+
+    // part 2
+    // demo for how to use customized color.
+     
+    TF1* func = new TF1("func", "sin(x)", -1, 1 );
+
+    // put in the color idx  
+    func->SetLineColor( myColor_idx  ); 
+    
+    func->SetLineWidth( 10 );
+    func->Draw();
+}
+

color_demos/_01_customized_color.py

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+import ROOT 
+
+""" This script demo how to set customize color """
+
+# color picker
+# https://www.w3schools.com/colors/colors_picker.asp 
+
+rgb = (146, 50, 195) # light purple.
+# normally, each r, g, b ranges from 0 to 255,
+# but in ROOT, each r, g, b range from 0 to 1.
+# so you have to divide them by 255.
+
+
+# we have to find a free color index to register our color 
+# it can be done by TColor::GetFreeColorIndex()
+# then construct the color.
+myColor_idx = ROOT.TColor.GetFreeColorIndex()
+myColor = ROOT.TColor( myColor_idx, rgb[0]/255., rgb[1]/255., rgb[2]/255. ); 
+
+
+# just use TF1 object to demo the color. 
+func = ROOT.TF1("func", "sin(x)", -1, 1 )
+func.SetLineColor( myColor_idx  )  # put in the color idx.
+func.SetLineWidth( 10 )
+func.Draw()

color_demos/_02_built_in_color.py

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+import ROOT 
+
+ 
+# TColor Reference
+# https://root.cern.ch/doc/master/classTColor.html
+
+if( 0 ):
+    # to show the color_index for built-in 50 colors  
+    
+    canvas_1 = ROOT.TCanvas("canvas_1","50 basic colors");
+    
+    canvas_1.DrawColorTable();
+
+    # usage: xxx.SetLineColor( color_index )
+
+
+
+if( 0 ):
+
+    # there are 15 color names   
+
+    color_names\
+    = ( ROOT.kWhite, ROOT.kBlack,  ROOT.kGray,    ROOT.kRed,   ROOT.kGreen,\
+        ROOT.kBlue , ROOT.kYellow, ROOT.kMagenta, ROOT.kCyan,  ROOT.kOrange,\
+        ROOT.kSpring, ROOT.kTeal,  ROOT.kAzure,   ROOT.kViolet,ROOT.kPink )
+
+     
+    canvas_2 = ROOT.TCanvas("canvas_2","color name");
+    canvas_2.Range( 0, 0, 5, 3 );
+    
+    # use box to demo the colors.
+    box = ROOT.TBox();
+    box.SetFillStyle(1001)
+    x1 = 0.2; x2=0.8;  y1 = 0.2; y2=0.8
+    
+    for idx in range(15):
+        box.SetFillColor( color_names[idx] )  
+        box.DrawBox( x1, y1, x2, y2 );
+
+        # to check the position.
+        # print "idx=%2d, x1 =%4.1f, x2 =%4.1f, y1 =%4.1f, y2 =%4.1f " \
+        # %(idx, x1, x2, y1, y2 )
+    
+        x1 +=1; x2+=1;
+
+        # to move to upper row.
+        if( (idx+1) %5 ==0 ): 
+            x1 = 0.2; x2=0.8; 
+            y1+=1; y2+=1
+        
+
+
+
+if( 1 ):
+    canvas_3 = ROOT.TCanvas("canvas_3","color wheel", 800, 800);
+    colorwheel = ROOT.TColorWheel();
+   
+    colorwheel.SetCanvas( canvas_3 );
+    colorwheel.Draw();
+
+    # usage: xxx.SetLineColor( ROOT.kRed+2 )
+    pass
+

color_demos/_03_contour.py

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+import ROOT 
+from array import array
+
+# in this script, we discuss how to set contour layers.
+
+PI = ROOT.TMath.Pi()
+
+# create a canvas, and draw a function z=f(x,y).
+canvas_1 = ROOT.TCanvas("canvas_1","");
+func = ROOT.TF2("f2","cos(x)*cos(y)", -PI/2,PI/2, -PI/2, PI/2);
+func.SetLineWidth(2); # the mesh
+func.SetLineColor(ROOT.kGray);
+
+if( 0 ):
+    #  example 1
+    # by default for surf1z, we have colors for 20 layers.
+    # and z values are equally divided.
+    func.Draw("surf1z")
+    
+
+
+if( 0 ):
+    #  example 2
+    # Let's use just 4 colors, and set z values are equally divided 
+    nLevels = 4
+    func.SetContour( nLevels )
+    func.Draw("surf1z")
+
+if( 0 ):
+    #  example 3
+    #  4 colors, but  z values are non-equally divided 
+    #  from the previous example or formula, we know z ranges from 0 to 1.
+    
+    #  suppose, we want to divide in the following way:
+    #   0----0.7-----0.8------0.9------>inf
+    #    col1 |  col2 |  col3  |  col4
+    nLevels = 4
+    cutValueArray = array( 'd', [ 0, 0.7, 0.8, 0.9 ] )
+    func.SetContour( nLevels, cutValueArray )
+    func.Draw("surf1z")
+     
+
+if( 1 ):
+    pass 
+    #  example 4
+    #  customized Palette
+    #  let's say, we still want the division setting from example3
+    #  but we want to customize our colors.
+    #  we define 4 colors : 
+    #  color1 = 232, 185, 171
+    #  color2 = 224, 152, 145
+    #  color3 = 203, 118, 158
+    #  color4 = 140,  95, 102
+    #  note: you can set more colors, but since we only have nLevels =4
+    #  there redundant colors will not be shown.
+
+    rgb_set = [ (232, 185, 171), (224, 152, 145),\
+                (203, 118, 158), ( 140, 95, 102)]
+    
+    myColorIdxList = []
+    myColors = []
+    for i in range( len(rgb_set) ):
+
+        myColorIdx = ROOT.TColor.GetFreeColorIndex()
+        myColorIdxList.append( myColorIdx )
+        
+        rgb = rgb_set[i]
+        myColor = ROOT.TColor( myColorIdx, rgb[0]/255., rgb[1]/255., rgb[2]/255. ); 
+        myColors.append( myColor )
+
+    colorAarry = array( 'i', myColorIdxList )
+    ROOT.gStyle.SetPalette( len(colorAarry), colorAarry )
+    # there are many default Palette.
+    # https://root.cern.ch/doc/master/classTColor.html
+
+    # the following is the same for example3
+    nLevels = 4
+    cutValueArray = array( 'd', [ 0, 0.7, 0.8, 0.9 ] )
+    func.SetContour( nLevels, cutValueArray )
+    func.Draw("surf1z")
+