[2005] Graphics.DrawImage incorrectly scaling an image?

[agent]

I'm writing some code that draws a barcode at a given size and scales it. It starts off with an image that varies in width but is always one pixel in height.

When I'm ready to draw the barcode, it scales the image to fit into a label control (a simple call to e.Graphics.DrawImage(...) in the Paint event).

What I'm getting, however is a barcode that is half the height of the label control, regardless of the size of the label control.

To use this, create a new form with a text box and a label. Label.autosize = false, text="". Anchor all four sides. Once running, type something into the text box. The code converts the 1 and 0 into black and white pixels respectively and sets a private field to the new bitmap. The label draws from this bitmap. Any ideas why it only fills half the label even though I provided label1.size to draw image? Seems like a bug.

Public Class Form1
 
    Private bc As Bitmap
 
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        If Not TextBox1.Text = "" Then
            Dim a As New BarcodeLib.Barcode
 
            'a.RawData = TextBox1.Text
            'a.EncodedType = BarcodeLib.TYPE.CODE128
            'a.Encode()
            'bc = BCFromEncodedData(a.EncodedValue)
 
            bc = BCFromEncodedData("1011001101100110110011011001101100110110011011001")
 
            Label1.Refresh()
        Else
            bc = Nothing
            Label1.Refresh()
        End If
    End Sub
 
    Private Function BCFromEncodedData(ByVal data As String) As Bitmap
        Dim a As New Bitmap(data.Length, 1, Imaging.PixelFormat.Format32bppArgb)
 
        For i As Integer = 0 To data.Length - 1
            If data(i) = "1" Then a.SetPixel(i, 0, Color.Black)
        Next
 
        Return a
    End Function
 
    Private Sub Label1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Label1.Paint
        e.Graphics.InterpolationMode = Drawing2D.InterpolationMode.NearestNeighbor
 
        If bc IsNot Nothing Then
            e.Graphics.DrawImage(bc, New Rectangle(Point.Empty, Label1.Size))
        End If
    End Sub
 
    Private Sub Label1_SizeChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Label1.SizeChanged
        Refresh()
    End Sub
End Class

[EntityX]

I ran your code. I pretty much got the results you were talking about.

There's a line that I commented out

Dim a As New BarcodeLib.Barcode

a wasn't being used in that sub.

Where you have

e.Graphics.DrawImage(bc, New Rectangle(Point.Empty, Label1.Size))

I tried experimenting with rectangle and got rid of Point.Empty, Label1.Size.

I came up with this instead.

          Dim w, h As Integer
            h = Label1.Height
            w = Label1.Width
            e.Graphics.DrawImage(bc, New Rectangle(0, 0, w, 2 * h))

I'm running Visual Basic 2008 not 2005. What's weird is that I had to multiply height of label by 2 to get the barcode to display taller. Don't know why.

I attached screenshots. First using your code and second using my code.

[agent]

whoops, forgot to comment that out myself. the Barcode reference isn't relevant to this problem, hence the other commented out code.

I figured I could just scale it to twice the height, but I'm curious as to why it's doing this in the first place.

[jmcilhinney]

Have you tested similar things with other images?

Also, this is an odd way to display a barcode. They are usually done by displaying text in a specific font.

[agent]

...Also, this is an odd way to display a barcode. They are usually done by displaying text in a specific font.

Actually, this is more common than you think, especially in codes where there is not a 1:1 ratio of segments (combination of bars) to digits. Examples include upc-a (half the code is black-white inverted from the other half) and pharmacode (the bars are a binary representation of a single number).

I need absolute control over the size of the code and may need to stretch it vertically. Unlike regular text, 1-dimensional barcodes don't have to maintain an aspect ratio to be readable. This is why I start with a bitmap one pixel in height. It's easier to set individual pixels than to draw a bunch of boxes (bars).

Not to mention, I have zero budget for this project. I can't purchase a font or five to make this work.