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Calculate height and width of GIF/JPG files(6) AfterError:
retVal(Lbound(retVal)) = w
retVal(Ubound(retVal)) = h
Close #f
ImageSize = retVal
End Function
Here's a sample GIFFile class cloning ImageSize() routine original logic:
Private Const GIF_HEADER_LENGTH = 10
Private Const GIF_MARKER = "GIF"
Private Const GIF_ID1 = "87a"
Private Const GIF_ID2= "89a"
Private Class GIFFile
Private m_w As Integer
Private m_h As Integer
Public Property Set fileName As String
Dim h ' GIF file Header: "GIF87a" or GIF89a" followed by logical width & height
h = Me.Header ' Let's check GIF format presence..
If ( Left$( h, 3 ) <> GIF_MARKER ) Then Error 1000, _
Not a GIF file: Graphical Interchange File "GIF" marker not found
If ( Mid$( h, 4, 3 ) <> GIF_ID1 And Mid$( h, 4, 3 ) <> GIF_ID2 ) Then Error 1002, _
Not a GIF file: Graphical Interchange File "87a/89a" identifier not found
m_w = Asc( Mid( h, 8, 1 ) ) * 256 + Asc( Mid( h, 7, 1 ) ) ' Little-endian Screen Width
m_h = Asc( Mid( h, 10, 1 ) ) * 256 + Asc( Mid( h, 9, 1 ) ) ' Little-endian Screen Height
End Property
Private Property Get Header As Variant
Dim h As Integer
h% = Freefile()
Open Me.Name For Input Shared As #h
Header = Input( GIF_HEADER_LENGTH, #h )
Close #h
End Property
Public Property Get Heigth As Integer
Heigth = m_h
End Property
Public Property Get Width As Integer
Me.Width = m_w
End Property
Public Sub new( fileName As String )
Me.FileName = fileName
End Sub
End Class
I have added GIF format additional checks intended to detect files holding inaccurate extension/type
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