Bezier line graph

[l1marik]

I am looking for simple solution to draw line bezier curve from values in 2D array. I do not need any complex library, but solution with example.

Thank you!

Lukas

[blueb]

This might help you...

Code: Select all

; English forum: http://www.purebasic.fr/english/viewtopic.php?t=6511&highlight=
; Author: ricardo (updated for PB4.00 by blbltheworm + Andre)
; Date: 12. June 2003
; OS: Windows
; Demo: No

Structure PointAPI 
  x.l 
  y.l 
EndStructure 

Global Dim P.PointAPI(3) 

Procedure CreateBezier() 
  StartDrawing(WindowOutput(0))
    Red = RGB(255,0,0) 
    Blue = RGB(0,0,255) 
    P(0)\x = 0 
    P(0)\y = 0 
    P(1)\x = 80 
    P(1)\y = 10 
    P(2)\x = 150 
    P(2)\y = 70 
    P(3)\x = 130 
    P(3)\y = 230 
    
    LineXY(P(0)\x+10,P(0)\y+10,P(1)\x+10,P(1)\y+10,Blue) 
    Box(P(0)\x+10,P(0)\y+10, 4, 4,Red) 
    Box(P(1)\x+10,P(1)\y+10, 4, 4,Red) 
    
    LineXY(P(2)\x+10,P(2)\y+10,P(3)\x+10,P(3)\y+10,Blue) 
    Box(P(2)\x+10,P(2)\y+10, 4, 4,Red) 
    Box(P(3)\x+10,P(3)\y+10, 4, 4,Red) 
    hDC = GetDC_(GadgetID(1)) 
    PolyBezier_(hDC,@P(),4) 
  StopDrawing() 
EndProcedure 


If OpenWindow(0,100,150,450,300,"Create Beizer Curve",#PB_Window_SystemMenu) 
 
  ImageGadget(1,10,10,255,255,0) 
  ButtonGadget(3,300,140,50,25,"Curve") 
  Repeat 
    EventID=WaitWindowEvent() 
    
    Select EventID 
    
      Case #PB_Event_Gadget 
        Select EventGadget() 
            
          Case 3 
            CreateBezier() 

        EndSelect 
    
    EndSelect 
    
  Until EventID=#PB_Event_CloseWindow 
EndIf 

[skywalk]

DeCasteljau Spline

[l1marik]

Because I really needed solution I made tiny implementation of Centripetal Catmull–Rom spline algorithm.

Bezier Curve Chart


Source: http://www.ctvrtky.info/wp-content/uplo ... bezier.zip

[l1marik]

Uploaded solution

[Saki]

Please use EnableExplicit.
It is very annoying if you have to add this yourself afterwards.

This you must not declare self, it's predefined on PB as Structure "Point"

Code: Select all

Structure struct_point
  x.i
  y.i
EndStructure

See here, Result is not "Potected"

Code: Select all

Procedure Min(a, b)
  If a <= b 
    Result = a
  Else
    Result = b
  EndIf
  ProcedureReturn Result
EndProcedure

Also use not "Define" inside Procedures, this get quick mismatch with "Global", at the same.
And again, code without EnableExplicit, has a Trapdoor

Code: Select all

Procedure Min_Array(Array a(1))
  Define Result
  Result = a(0)
  For i = 0 To ArraySize(a()) - 1
    If Result >= a(i) 
      Result = a(i)
    EndIf
  Next 
  ProcedureReturn Result

Why you refuse EnableExplicit is hard to understand, too bad - Plonk

[l1marik]

Dear Saki, updated by your reccomendation, only I kept own structure for y,x points.

Can somebody check it on Windows and OSX?

THX
Lukas

[Mindphazer]

Hi Lukas,

I've just checked on OS X, it seems to work fine. Nice job !

[kpeters58]

Can somebody check it on Windows and OSX?
THX
Lukas

Works fine under Windows 10 and looks very nice.

I noticed that you only implemented part of Saki's suggestions. Since I don't know whether you didn't understand what he was suggesting or if you just didn't feel like it, I have modified your code as per below to work without a single global variable.

If I'm telling you something you already know, my apologies: Globals are deemed undesirable by most experienced members of the programming communities - hence a slew of new(er) languages that don't support them at all: Haskell, V etc.

Code: Select all

EnableExplicit

Structure struct_point
  x.i
  y.i
EndStructure

Declare Min_Array(Array a(1))
Declare Max_Array(Array a(1))
Declare Min(a, b)
Declare Max(a, b)
Declare Draw_Chart(gid, Array chart_data(1), in_width, in_height, bgcol = 0, frontcol = 0)
Declare.s catmullRom2bezier(Array points.struct_point(1))

; -----------------------------------------------------------------------------------------
Procedure Min_Array(Array a(1))
  Protected result = a(0), i
  
  For i = 0 To ArraySize(a()) - 1
    If result >= a(i) 
      result = a(i)
    EndIf
  Next 
  ProcedureReturn result
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure Max_Array(Array a(1))
  Protected result = a(0), i
  
  Result = a(0)
  For i = 0 To ArraySize(a()) - 1
    If Result <= a(i) 
      Result = a(i)
    EndIf
  Next 
  ProcedureReturn Result
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure Min(a, b)
  ProcedureReturn (a * Bool(a <= b) + b * Bool(b < a))
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure Max(a, b)
  ProcedureReturn (a * Bool(a >= b) + b * Bool(b > a))
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure.s catmullRom2bezier(Array points.struct_point(1))
  Protected out_string.s = "", i, j
  
  For i = 0 To ArraySize(points()) - 2
    Dim p.struct_point(4) ; no need for protected keyword here - new arrays are always local
    
    If i > 0
      p(0)\x = points(Max(i - 1, 0))\x
      p(0)\y = points(Max(i - 1, 0))\y
    Else
      p(0)\x = points(i)\x
      p(0)\y = points(i)\y
    EndIf
    
    p(1)\x = points(i)\x
    p(1)\y = points(i)\y
    
    p(2)\x = points(i + 1)\x
    p(2)\y = points(i + 1)\y
    
    p(3)\x = points(Min(i + 2, ArraySize(points()) - 1))\x
    p(3)\y = points(Min(i + 2, ArraySize(points()) - 1))\y
    
    ;     For j = 0 To ArraySize(p())-1
    ;       Debug Str(p(j)\x) + "/" + Str(p(j)\y)
    ;     Next
    ;     Debug "-----------------------"
    
    ;Catmull-Rom To Cubic Bezier conversion matrix
    ;  0       1       0       0
    ;-1/6      1      1/6      0
    ;  0      1/6      1     -1/6
    ;  0       0       1       0
    
    Dim bp.struct_point(3) ; no need for protected keyword here - new arrays are always local
    bp(0)\x = (-p(0)\x + 6 * p(1)\x + p(2)\x) / 6
    bp(0)\y = (-p(0)\y + 6 * p(1)\y + p(2)\y) / 6
    
    bp(1)\x = (p(1)\x + 6 * p(2)\x - p(3)\x) / 6
    bp(1)\y = (p(1)\y + 6 * p(2)\y - p(3)\y) / 6
    
    bp(2)\x = p(2)\x
    bp(2)\y = p(2)\y
    
    FreeArray(p()) 
    
    Out_String = Out_String + "C "
    
    For j = 0 To ArraySize(bp()) - 1
      Out_String = Out_String + Str(bp(j)\x) + " " + Str(bp(j)\y) + " "
    Next
    
    FreeArray(bp())
  Next
  ProcedureReturn out_string
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure Draw_Chart(gid, Array chart_data(1), in_width, in_height, bgcol = 0, frontcol = 0)
  Protected x_resolution.f, y_resolution.f, y_middle.f, text.s, x.f, y.f, i
  
  x_resolution = in_width/ArraySize(chart_data())
  y_resolution = in_height/Abs(Max_Array(chart_data()) - Min_Array(chart_data()))
  y_middle = Abs(Max_Array(chart_data()) - Min_Array(chart_data())) / 2
  
  Dim chart.struct_point(ArraySize(chart_data()))
  
  For i = 0 To ArraySize(chart_data()) - 1
    chart(i)\x = ((i + 1) * x_resolution )
    chart(i)\y = (-chart_data(i) * y_resolution / 2) + 2 * in_height / 3
  Next
  
  If StartVectorDrawing(CanvasVectorOutput(gid))
    ScaleCoordinates(DesktopResolutionX(), DesktopResolutionY())
    AddPathBox(0, 0, in_width, in_height)
    VectorSourceColor(RGBA(0, 0, 0, 255))
    FillPath()
    ClosePath()
    
    For i = 0 To ArraySize(chart_data())
      AddPathBox(i * (x_resolution + x_resolution/500) - x_resolution/2, in_height / 11.4, x_resolution -(x_resolution / 50), in_height)
    Next
    VectorSourceLinearGradient(i * (x_resolution + x_resolution/500) - x_resolution / 2, in_height / 11.4, i * (x_resolution + x_resolution / 500) - x_resolution / 2, in_height)
    VectorSourceGradientColor(RGBA(0, 0, 0, 0), 0)
    VectorSourceGradientColor(RGBA(255, 255, 255,   0), 0.01)
    VectorSourceGradientColor(RGBA(255, 255, 255, 200), 0.15)
    VectorSourceGradientColor(RGBA(0, 0, 0, 0), 0.98)
    ClosePath()
    FillPath()
    
    AddPathBox(0, 0, in_width, in_height)
    If bgcol = 0 : bgcol = RGBA(0, 0, 0, 255):EndIf
    VectorSourceColor(bgcol)
    FillPath()
    ClosePath()
    
    ; Chart line
    MovePathCursor(0, (-chart_data(0) * y_resolution / 2) + 2 * in_height / 3)
    AddPathSegments(catmullRom2bezier(chart()))
    VectorSourceLinearGradient(0, 0, in_width, 0)
    VectorSourceGradientColor(RGBA(0, 0, 0, 0), 0)
    VectorSourceGradientColor(RGBA(255, 255, 255,   0), 0.02)
    VectorSourceGradientColor(RGBA(255, 255, 255, 255), 0.10)
    VectorSourceGradientColor(RGBA(255, 255, 255, 255), 0.90)
    VectorSourceGradientColor(RGBA(255, 255, 255,   0), 0.98)
    VectorSourceGradientColor(RGBA(0, 0, 0, 0), 1)
    StrokePath(in_height / 150)
    
    ; Chart area
    MovePathCursor(in_width, in_height)
    AddPathLine(0, in_height)
    AddPathLine(0, (-chart_data(0) * y_resolution / 2) + 2 * in_height / 3)
    AddPathSegments(catmullRom2bezier(chart()))
    VectorSourceLinearGradient(0, 0, in_width, 0)
    VectorSourceGradientColor(RGBA(0,0,0, 0), 0)
    VectorSourceGradientColor(RGBA(255, 255, 255,  0), 0.02)
    VectorSourceGradientColor(RGBA(255, 255, 255, 40), 0.20)
    VectorSourceGradientColor(RGBA(255, 255, 255, 40), 0.80)
    VectorSourceGradientColor(RGBA(255, 255, 255,  0), 0.98)
    VectorSourceGradientColor(RGBA(0, 0, 0, 0), 1)
    FillPath()
    
    ; Chart headers
    For i = 1 To ArraySize(chart_data()) - 1
      AddPathBox(i * (x_resolution + x_resolution / 500) - x_resolution / 2, 0, x_resolution - (x_resolution / 50), in_height / 12)
    Next
    VectorSourceColor(RGBA(255, 255, 255, 50))
    ClosePath()
    FillPath()
    ; Chart headers labels - to be added
    
    ; Chart values
    VectorSourceColor(RGBA(255, 255, 255, 200))
    VectorFont(FontID(0), x_resolution / 2.5)
    For i = 1 To ArraySize(chart_data()) - 1
      text = StrF(chart_data(i - 1) / 10, 1)
      x = i * (x_resolution + x_resolution / 500) - x_resolution / 2
      x = (x + ((x_resolution - (x_resolution / 50)) / 2)) - VectorTextWidth(text) / 2
      MovePathCursor(x, in_height / 8)
      DrawVectorText(text)
    Next
    StopVectorDrawing()
  EndIf
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure Resize_Window()
  Protected i
  Dim chart_dataset(24) ; no need for protected keyword here - new arrays are always local
  
  For i = 0 To ArraySize(chart_dataset()) - 1
    chart_dataset(i) = (Random(100, 0) - 30)
  Next
  ResizeGadget(0, 0, 0, WindowWidth(0), WindowHeight(0))
  Draw_Chart(0, chart_dataset(), WindowWidth(0), WindowHeight(0), RGBA(Random(30, 0), Random(55, 0), Random(55, 0), Random(200, 100)))
EndProcedure

; -----------------------------------------------------------------------------------------
Procedure StartProgram()
  Protected Event
  
  If OpenWindow(0, 0, 0, 400, 200, "Bezier Curve Chart", #PB_Window_SystemMenu | #PB_Window_ScreenCentered| #PB_Window_SizeGadget| #PB_Window_MaximizeGadget)
    CanvasGadget(0, 0, 0, WindowWidth(0), WindowHeight(0))
    AddWindowTimer(0, 123, 1000)
    LoadFont(0, "Ubuntu", 10, #PB_Font_HighQuality)
    Resize_Window()
    ;
    BindEvent(#PB_Event_SizeWindow, @Resize_Window(), 0)
    BindEvent(#PB_Event_Timer, @Resize_Window(), 0)
    ;
    Repeat
      Event = WaitWindowEvent()
    Until Event = #PB_Event_CloseWindow
  EndIf
EndProcedure

; -----------------------------------------------------------------------------------------
StartProgram()

[dige]

Looks very good! Thx for sharing!