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Thread: Drawing a map

  1. #1
    Join Date
    Jan 2006

    Drawing a map


    I am trying to draw a map in a picturebox. First I load the base image which is a 1024x1024 bitmap of the map (no annotations) from Private Sub draw_map(), then to add all the map synbols, the data is collected from a simple text file, analysed and then drawn over the base map using x y coordinates. This is called from Private Sub draw_objects()

    So when the form containing the picturebox loads it runs
    The strange thing is that all the objects are drawn first, then the map, over the objects (or the objects disappear again, I don't know). I tried doing it from the form_Paint but that only results in the symbols reloading endlessly and flashing on the screen.

    I'm thinkig of going back to VB6

    I am so new to this so be gentle

  2. #2
    Join Date
    Nov 2003
    Portland, OR
    Please post a sample of your code from the draw_objects function. Are you sure you're drawing the objects on the picturebox and not on the form?
    Phil Weber

    Please post questions to the forums, where others may benefit.
    I do not offer free assistance by e-mail. Thank you!

  3. #3
    Join Date
    Jan 2006
    Quote Originally Posted by Phil Weber
    Please post a sample of your code from the draw_objects function. Are you sure you're drawing the objects on the picturebox and not on the form?
    Thanks for replying Phil, I will try to provide som code here (the pictureBox is names picChart) :

    Private Sub draw_map()
       Dim vsImage As Image
       vsImage = System.Drawing.Image.FromFile(vsPath & "simple.bmp")
       picChart.Image = vsImage
    End Sub
    So far so good, this displays as it should. Then to load the map symbols it uses

    Private Sub draw_objects()
       Dim drawSymbol As System.Drawing.Graphics
       drawSymbol = picChart.CreateGraphics
       objImage = System.Drawing.Image.FromFile("C:\bla bla bla\images\buoy.gif")
       drawSymbol.DrawImage(objImage, xCoord - 5, yCoord - 5, 10, 10)
    End Sub
    This is only a part of the code where it draws the buoy.gif onto the map.
    (The xCoord and yCoord are calculated from Latitude/Longitude values in the objects.txt file)

    Then the final part is

    Private Sub picChart_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles picChart.Paint
    End Sub
    My understanding is that using the _Paint will replace the AutoRedraw previosly used in VB6.

    I've also tried running the draw_map and draw_object on the form Load but that will only show the objects loading once and then clear them. At least this way keeps them flashing on the screen so I can see them

    Please let me know if you need any more code, I'm not really sure what I should be showing here.

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