Copying and pasting a non-rectangular area of screen

[ahenry3068]

Has anyone made a routine to copy a paste a non-rectangular area of the screen?  Or does QB64PE have a built-in way?  I'm working on a new drawing program and trying to add a feature where you can draw an enclosed area with the mouse, copy it, and paste it.  Making a circle area routine was easy, but having some difficulty with the any shape one.  I'm doing a polygon approach for the any shaped one, capture all the pixels inside the drawn polygon.   Wondered if someone here has already made such a routine that is working.

Here's the circle copy/paste that is working ok.

- Dav

Code: (Select All)

Screen _NewImage(1000, 700, 32)



For t = 1 To 7000

    Color _RGB(Rnd * 255, Rnd * 255, Rnd * 255)

    Print _Trim$(Str$(Int(Rnd * 10)));

Next



Circle (100, 100), 51, _RGB(255, 255, 255)

x& = GetCircle&(100, 100, 50)



Locate 2, 24:: Color _RGB(255, 255, 255)

Print "  Copied this area of the screen  "

_Delay 2



Cls



Do

    PutCircle Rnd * _Width, Rnd * _Height, x&, Rnd * 255

    _Limit 30

Loop Until InKey$ <> ""







Function GetCircle& (cx, cy, radius)



    If circleimg& <> 0 Then _FreeImage circleimg&



    circleimg& = _NewImage(radius * 2, radius * 2) '



    _Dest circleimg&



    For x = 0 To radius * 2

        For y = 0 To radius * 2

            If Sqr((x - radius) ^ 2 + (y - radius) ^ 2) <= radius Then

                clr& = Point(cx - radius + x, cy - radius + y)

                PSet (x, y), clr&

            End If

        Next

    Next



    GetCircle& = _CopyImage(circleimg&)

    _FreeImage circleimg&



    _Dest 0



End Function



Sub PutCircle (cx, cy, img&, alpha)



    If img& = 0 Then Exit Sub



    radius = _Width(img&) / 2



    _Source img&

    _Dest 0



    For x = 0 To radius * 2

        For y = 0 To radius * 2

            If Sqr((x - radius) ^ 2 + (y - radius) ^ 2) <= radius Then

                clr~& = Point(x, y)

                r = _Red32(clr~&)

                g = _Green32(clr~&)

                b = _Blue32(clr~&)

                PSet (cx + x, cy + y), _RGBA(r, g, b, alpha)

            End If

        Next

    Next



    _Source 0



End Sub

       I don't have any code handy but I have a good idea how you must go about it.      Because of how Video Ram is layed out _PutImage & _GetImage only operate on rectangular images.  I believe you MUST be in 32 bit color mode to do this but what you have to do is do a _GetImage of what you want.     Then Mask out the shape with pixels that have an _Alpha (opacity) value of 0.    Then when you do the _PutImage the ALPHA=0 pixels will not be visible.      Depending on the shape the masking code will be different.    Your code is clever but I have the feeling that it might be to slow for animation.    (Maybe not though,  It is a bit amazing how fast modern computers are.   But my code mind set is stuck on slower systems)