Graphics 640,480
SetBuffer BackBuffer()
SeedRnd MilliSecs()
Type segment
Field angle#
Field value#
End Type
; just some sizes for the pie chart, based on the graphics resolution, so it will scale ok.
Global pie_chart_start_x# = GraphicsWidth()/2
Global pie_chart_start_y# = GraphicsHeight()/2
Global pie_chart_size# = GraphicsHeight()/2.2
Global segment_text_position# = 0.75 ; a value between 0 and 1: 0 = at the middle. 1 = at the edge.
Global total_value ; this is calculated below, when generating the type object segments.
; create 6 chart segments
For loop = 1 To 6
s.segment = New segment
s\value# = Rand(10,100)
total_value = total_value + s\value
Next
While Not KeyHit(1)
Cls
draw_pie_chart()
Flip
Wend
Function draw_pie_chart()
; draw the circle shape of the pie chart. use the start X and Y and the pie chart size here.
Oval pie_chart_start_x - pie_chart_size, pie_chart_start_y - pie_chart_size,pie_chart_size*2,pie_chart_size*2,0
Local angle# = 90 ; set this to 90 to overcome blitz rotation system, so it start vertically.
Local angle_gap# ; used to work out the angle size, based on the value in the type object.
; as always: (value / total value)*100 gives you a percentage.
Local text_angle#; i take half of the angle_gap and use this angle to place the visual value.
; draw initial line
Line pie_chart_start_x, pie_chart_start_y, pie_chart_start_x - (Cos(angle)*pie_chart_size), pie_chart_start_y - (Sin(angle)*pie_chart_size)
; draw the total value
Text pie_chart_start_x, pie_chart_start_y - (pie_chart_size*1.05), total_value,True,True
For s.segment = Each segment
angle_gap = 360 * (s\value / total_value)
text_angle = angle_gap/2
angle = angle + angle_gap
; BELOW: draw a line to show the segment.
Line pie_chart_start_x, pie_chart_start_y, pie_chart_start_x - (Cos(angle)*pie_chart_size), pie_chart_start_y - (Sin(angle)*pie_chart_size)
; BELOW: place the visual value of the type object, halfway between the centre and circumfirance.
Text pie_chart_start_x - (Cos(angle - text_angle)*(pie_chart_size*segment_text_position)), pie_chart_start_y - (Sin(angle - text_angle)*(pie_chart_size*segment_text_position)),s\value,True,True
Next
End Function |
