I've been with a problem for about two months and i've bought books and
search the internet for an explanation, and haven't found one.
I'm developing a cephalometric software, that needs to capture an image from
the scanner, mark the image with dots in order to find distances and angles.
Everything is ok except when i try to zoom in/zoom out the image. Every
calculated angle and distance becomes variable because when i use the zoom
the dots have to be repositioned on the image, acording to the pacient face
I'm using a "picturebox" and the "Zoom" value in the "SizeMode" property
when i try to zoom in i'm using the following code on the button:

Private Sub ZoomIn_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles ZoomIn.Click
    Dim intWidthAnterior As Integer, intWidthPosterior As Integer
        Dim intHeightAnterior As Integer, intHeightPosterior As Integer
        Dim sngDpiX As Single, sngDpiY As Single
        Dim g As Graphics = picDraw.CreateGraphics


        sngDpiX = g.DpiX
        sngDpiY = g.DpiY
        intWidthAnterior = picDraw.Width
        intHeightAnterior = picDraw.Height
        picDraw.Width = picDraw.Width * 1.2      'Here i'm making the
picturebox larger
        picDraw.Height = picDraw.Height * 1.2    'Here i'm making the
picturebox larger
        intWidthPosterior = picDraw.Width
        intHeightPosterior = picDraw.Height

        MainDrawPics.RedefinePontosAdicao(intWidthAnterior,
intHeightAnterior, intWidthPosterior, intHeightPosterior, picDraw, sngDpiX,
sngDpiY)
        picDraw.Refresh()
End Sub

'And this function is used to reposition the dots (point) on the screen
Friend Overloads Sub RedefinePontosAdicao(ByVal intWidthPictureBoxAnterior
As Integer, ByVal intHeightPictureBoxAnterior As Integer, _
                                              ByVal
intWidthPictureBoxPosterior As Integer, ByVal intHeightPictureBoxPosterior As
Integer, _
                                              ByVal picDesenho As
System.Windows.Forms.PictureBox, ByVal sngDesenhoDpix As Single, _
                                              ByVal sngDesenhoDpiy As Single)

        Dim intContador As Integer
        Dim intResultado As Integer
        Dim sngFactor As Single = 1.2


    'I have an array with all the dots that have been marked on the patient
face, and this procedure
        'tries to reposition the dots on the screen in order to show the
user the place where he clicked
        'but in a larger scale
        For intContador = 0 To UBound(ArrayPontos) - 1
            intResultado = CInt(ArrayPontos(intContador).lngValorX *
sngFactor)
            ArrayPontos(intContador).lngValorX = intResultado
            intResultado = CInt(ArrayPontos(intContador).lngValorY *
sngFactor)
            ArrayPontos(intContador).lngValorY = intResultado
        Next
End Sub

I'm really desperate!
My thanks in advanced

Ricardo Furtado wrote:
If you work in a world-space then the positions of the dots are always the
same.
Transform from world-space to screen-space when you display it, and have a
reverse transformation from screen-space to world-space for identifying
where the user clicked.


<snip>
Surely that should be UBound(ArrayPontos) without subtracting 1?

I suspect you aren't taking into account the origin when you're scaling.

It would be easier if you put screen grabs of what happens and what you want
to happen on a web page somewhere so we can see what's going wrong.

Andrew

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