How to scale polygons mapped to a resizeing picture
Im craeating a dart scoring program (to use myself in my dart room) and want the user to be able to click in different areas of a picture of a dart board to register the thrown darts.
This program will be resizable, so the picture of the dart board can change it's size when the user change the program window size.
Im using a list of polygons(pointF-arrays) to map up each area and run some calculation to see if the mouse click is inside the polygons area, but how do I scale those polygons correctly when the picturebox is resized? My polygons are hard coded to map the dartboards area of the picture at a specific size.
Edit: After the the really brilliant answer from Olivier Jacot-Descombes, I fixed the scaling with a GetScaledPoint-function that transform the mousepointer x and y value to values matching the original picture size, making it easy to check for hits in the original polygons. I have edited in the solution in the code below if anyone is interrested. In this example, Picture1 is a picture of a dart board (like this one http://quizmasters.biz/Pub%20Genius/Darts/Gfx/Dartboard_05.jpg) that is set to sizemode=stretch and docking=fill.
Public Class DartBoard
Dim Double20 = New PointF() {New PointF(263, 78), New PointF(275, 76), New PointF(284, 76), New PointF(293, 75), New PointF(306, 75), New PointF(319, 75), New PointF(332, 76), New PointF(330, 89), New PointF(320, 88), New PointF(309, 87), New PointF(300, 87), New PointF(289, 88), New PointF(277, 89), New PointF(267, 91), New PointF(264, 78)}
Dim Triple20 = New PointF() {New PointF(279, 154), New PointF(285, 154), New PointF(293, 154), New PointF(301, 152), New PointF(306, 152), New PointF(312, 152), New PointF(314, 151), New PointF(322, 152), New PointF(320, 167), New PointF(312, 165), New PointF(304, 164), New PointF(297, 165), New PointF(289, 166), New PointF(281, 166), New PointF(277, 154), New PointF(283, 153), New PointF(291, 153), New PointF(299, 15开发者_如何学JAVA2), New PointF(308, 152), New PointF(314, 153), New PointF(322, 153)}
Private startwidth As Integer = 0
Private startheight As Integer = 0
Public Structure DartBoardAreaStruct
Public Points As Integer
Public Area() As PointF
End Structure
Dim DartBoardAreas As New List(Of DartBoardAreaStruct)
Private Sub DartBoard_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
DartBoardAreas.Add(New DartBoardAreaStruct With {.Area = Double20, .Points = 40})
DartBoardAreas.Add(New DartBoardAreaStruct With {.Area = Triple20, .Points = 60})
startwidth = PictureBox1.Width
startheight = PictureBox1.Height
End Sub
Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
Dim scaledpos As PointF = GetScaledPoint(e.Location)
For Each DartBoardArea In DartBoardAreas
If Me.PolyGonHitTest(DartBoardArea.Area, scaledpos) Then
MsgBox(DartBoardArea.Points)
End If
Next
End Sub
Public Function PolyGonHitTest(ByVal polygonPoints() As PointF, ByVal mousePos As PointF) As Boolean
Dim path As New System.Drawing.Drawing2D.GraphicsPath
path.AddLines(polygonPoints)
Dim region As New Region(path)
If region.IsVisible(mousePos) Then Return True
Return False
End Function
Function GetScaledPoint(ByVal s As Point) As PointF
Dim xfactor As Double = 0
Dim yfactor As Double = 0
Dim OriginalSize As Size = New Size(startwidth, startheight)
Dim NewSize As Size = New Size(PictureBox1.Width, PictureBox1.Height)
If NewSize.Width < OriginalSize.Width Then
xfactor = OriginalSize.Width / NewSize.Width
Else
xfactor = NewSize.Width / OriginalSize.Width
End If
If NewSize.Height < OriginalSize.Height Then
yfactor = OriginalSize.Height / NewSize.Height
Else
yfactor = NewSize.Height / OriginalSize.Height
End If
Return New PointF(s.X / xfactor, s.Y / yfactor)
End Function
End Class
A easy and fast solution would be to keep the polygons unchanged, but to scale the mouse coordinates. For instance you could have polygon coordiantes between 0.0f and 1.0f and scale your mouse coordinates like:
xScaled As Single = e.X/DartBoardArea.Width
yScaled As Single = e.Y/DartBoardArea.Height
scaledPos As PointF = new PointF(xScaled, yScaled)
精彩评论