Rotate image of windbarb around tip point

[jwyman]

Hello all,
I have a collection of windbarbs of different wind velocities that i need to have displayed on a map. I would like the image to use the bottom of the windbarb/tip ad the rotation point. This is needed because the windbarb is oriented in which the wind is coming from. Below is the routine i am using. The size of the windbarb image is 12px wide X 57px height.

 Private Function RotateImage(image As Image, angle As Single) As Bitmap
        ' the calling code is responsible for (and must) 
        ' disposing of the bitmap returned

        Dim retBMP As New Bitmap(image)
        retBMP.SetResolution(image.HorizontalResolution, image.VerticalResolution)

        Using g = Graphics.FromImage(retBMP)
            g.TranslateTransform(CSng(image.Width / 2), CSng(image.Height / 2))
            g.RotateTransform(angle)
            g.DrawImage(retBMP, New Point(-image.Width \ 2, -image.Height \ 2))
        End Using

        Return retBMP

    End Function

[.paul.]

Ok. First, always format code when you post it in this forum

[code]’ your code[/code]

Will format as…

’ your code

Secondly, you’ve posted code, and a brief description of your intentions, but you haven’t told us whether your code works, or what doesn’t work about it???

If you want to rotate around a point, you’d generally use [graphics].TranslateTransForm(x, y), before the rotate call…

[jwyman]

It appears that the image is rotating around the center of the image defined coordinates.

[jwyman]

I have attached an image of the map with the windbarb displayed. I need to have this image rotate around from 0-360 degrees with the pivot point being the base of the windbarb.

Attachment 185481

[jwyman]

Solution Found!

  Try

            Dim MaxSize As Integer

            Dim retBMP As New Bitmap(image)

            MaxSize = Math.Max(image.Width, image.Height) * 2

            Dim tempImage As New Bitmap(MaxSize, MaxSize)

            retBMP.SetResolution(image.HorizontalResolution, image.VerticalResolution)

            Using g = Graphics.FromImage(tempImage)

                g.TranslateTransform(CSng(tempImage.Width / 2), CSng(tempImage.Height / 2))

                g.RotateTransform(angle)

                g.DrawImage(retBMP, New PointF(0, -image.Height))

                g.ResetTransform()

                Return tempImage

            End Using



        Catch ex As Exception
            MsgBox(ex.Message & vbCrLf & ex.StackTrace)
        End Try