Pie Chart

This code has been declared by its author to be Public Domain code.

Pie Chart by Silver_Knee

2015

Draw a full colored pie chart by adding all pie chart pieces to an array. The angle given must be the angle the pie piece ends. The first pie piece will start at angle 0 that is straight down and the pieces are added counterclockwise. The first piece may have an angle of 10, the second an angle of 180, the third an angle of 200 and so on. To build a full pie, the last piece must have an angle of 360.

The code is only safe if all pieces are in order, so no angle is below an angle that came before it in the array, and all angles are between 0 and 360 inclusive.

The chart is drawn with straigt lines. In BB Rects were faster than straight lines, I don't know how it is with BlitzMax and the diffrent drivers here. Also, the code uses two for-loops, so it is probably slow for many pieces and a big radius.

Function DrawPieChart(x:Float, y:Float, pieces:TPieChartPiece[], radius:Float)
	Local lastAngle:Float=0
	For Local p:TPieChartPiece=EachIn pieces
		SetColor p.r,p.g,p.b
		For Local dy:Float= -radius To +radius Step 1
			'right half - cut to right half with Max here
			Local circleAngle:Float=ACos(dy/radius) 'min 0 / max 180

			If circleAngle<90
				'bottom
				If p.angle>circleAngle And circleAngle>lastAngle
					DrawLine x+Sin(circleAngle)*radius,y+dy,x+Tan(lastAngle)*dy,y+dy
				ElseIf p.angle<=circleAngle
					DrawLine x+Tan(p.angle)*dy,y+dy,x+Tan(lastAngle)*dy,y+dy			
				EndIf
			Else
				'top
				Local dx:Int
				If p.angle<=180
					dx=Tan(p.angle)*dy
				Else
					dx=0
				EndIf
				
				If p.angle>circleAngle And circleAngle>lastAngle
					DrawLine x+dx,y+dy,x+Sin(circleAngle)*radius,y+dy
				ElseIf p.angle>=circleAngle And lastAngle<=180
					DrawLine x+dx,y+dy,x+Tan(lastAngle)*dy,y+dy
				EndIf
			EndIf
			
			'left half - cut to left half with Min here
			circleAngle=360-circleAngle

			If circleAngle>270
				'bottom
				If p.angle>circleAngle And circleAngle>lastAngle
					DrawLine Min(x,x-Sin(360-circleAngle)*radius),y+dy,Min(x,x-Tan(360-p.angle)*dy),y+dy
				ElseIf p.angle>=circleAngle
					DrawLine Min(x,x-Tan(360-p.angle)*dy),y+dy,Min(x,x-Tan(360-lastAngle)*dy),y+dy
				EndIf
			Else
				'top 
				Local dx:Int
				If lastAngle>=180
					dx=-Tan(360-lastAngle)*dy
				Else
					dx=0
				EndIf
				
				If p.angle>circleAngle And circleAngle>lastAngle
					DrawLine x-Sin(360-circleAngle)*radius,y+dy,x+dx,y+dy
				ElseIf p.angle<=circleAngle And p.angle>180
					DrawLine x+Tan(p.angle)*dy,y+dy,x+dx,y+dy
				EndIf			
			EndIf
		Next 
		DrawLine x,y,x+Sin(p.angle)*radius,y+Cos(p.angle)*radius
		DrawLine x,y,x+Sin(lastAngle)*radius,y+Cos(lastAngle)*radius
		lastAngle=p.angle
	Next
End Function 

Type TPieChartPiece
	Function Create:TPieChartPiece(angle:Float,r:Int,g:Int,b:Int)
		Local this:TPieChartPiece=New TPieChartPiece
		this.angle=angle
		this.r=r
		this.g=g
		this.b=b
		Return this
	End Function
	
	Field angle:Float
	Field r:Int,g:Int,b:Int
End Type

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