Clip Rectangle To Rectangle

[kevin]

 Clip Rectangle To Rectangle

 In this example, we're clipping the background rectangle to the foreground rectangle. This results in 16 possible layouts that the pair of rectangles can have in relation to each other. The goal is to output a list of areas that represent the visible portion of the background rectangle without overlapping any pixels

PlayBASIC Code: [Select]

; PROJECT : Clip Foreground Rectangle TO Background Rectangle
; AUTHOR  : Kev Picone - https://playbasic.com
; CREATED : 8/04/2023
; EDITED  : 9/04/2023
; ---------------------------------------------------------------------

   loadfont "courier new",1, 40

   Type tRect
         x1,y1
         x2,y2
         Colour
   EndType
   
   Dim Rects(16) as tRect

   Global RectCount   =0

   do


      Dim Back as tRect Pointer
      Back = new TRect

      w= rndrange(100,500)
      h= rndrange(100,500)
      X=rnd( getscreenwidth() * 0.60)
      Y=rnd(getscreenheight() * 0.60)
      Back.x1 = x
      Back.y1 = y
      Back.x2 = x+w
      Back.y2 = y+h
      Back.colour =rndrgb()   

      Dim Front as tRect Pointer
      Front = new TRect
   
      W= 500
      H= 150
      
      // --------------------------------------------------------
      Do
      // --------------------------------------------------------
         cls $203040
      
            Boxc Back.x1,Back.y1,Back.x2,Back.y2,true,Back.Colour
   
   
            Front.x1=mousex()
               Front.y1=mousey()
            Front.x2=Front.x1+W
            Front.y2=Front.y1+H
   
            box Front.x1,Front.y1,Front.x2,Front.y2,true
   
   
            inkmode 1+1024
            Status =ClipRectangles(Front,Back)
            inkmode 1
   
            for lp =0 to Status-1
               X1=Rects(lp).x1
                  y1=Rects(lp).y1   
               x2=Rects(lp).x2   
               y2=Rects(lp).y2
               boxc x1,y1,x2,y2,false, $00ff00
               boxc x1+1,y1+1,x2-1,y2-1,false, $00ff00

               s$ =" X1="+str$(X1)
               s$+=" Y1="+str$(Y1)
               s$+=" Y1="+str$(X2)
               s$+=" Y1="+str$(Y2)

               Print "#"+str$(lp)+s$
                     
            next

            if Status=-2
               Print "Foreground covers background"
            endif

            if mousebutton()=2
                  w=rndrange(50,500)
                  h=rndrange(50,350)
            endif
   
         sync

      // --------------------------------------------------------
      loop spacekey()
      // --------------------------------------------------------

      free front
      free back

         
loop   




Function ClipRectangles(Front as tRect Pointer, Back as tRect Pointer)

      RectCount   =0
      Count = -1   

      if int(Front)=0 or int(Back)=0 then ExitFunction -1

      // chec if the Front rect to the left or right of te back rect
      if Front.X2<Back.X1 then exitfunction Count
      if Front.X1>Back.X2 then exitfunction Count
   
      //  check if the FRONT is ABOVE or BELLOW the BACK rect
      if Front.Y2<Back.Y1 then exitfunction Count
      if Front.Y1>Back.Y2 then exitfunction Count


      //  Make bit pattern for what side each point is to its patern
      Layout   = (Front.X1>=Back.X1 << 1)+ ( Front.X2>Back.X2) 
      Layout   =Layout<<2

      Layout+= Front.Y1>=Back.Y1 << 1
      Layout+= Front.Y2>Back.Y2 

      Filled   =true
      static ThisRGB   
      
      ThisRGB = -1
      
      print bin$(Layout)
      
      Select LayOut

            // ---------------------------------------------
            case %0000
            // ---------------------------------------------

                  //  front is covering back to left and 
                  //  above and bellow back
                  SetBox( Front.x2   ,Back.y1      ,back.x2   ,front.y2   , ThisRGB)
                  SetBox( Back.x1   ,front.y2   ,back.x2   ,back.y2      , ThisRGB)

            // ---------------------------------------------
            case %0001
            // ---------------------------------------------

                  //  front is covering back to left and 
                  //  above and bellow back

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