Read two .TIF files from an .IMG file

Question

Dealing with some legacy code that parses .TIF images (front and back images for checks) from an .IMG file. For example, I have the following file: 05090001.IMG and then I have the following values about that file:

FrontStart: 8 | FrontLength: 10600 | RearStart: 10608 | RearLength: 6372

The size of 05090001.IMG is 16980 bytes, so it seems that the front image should be 10600 bytes and does in fact create a valid .TIF file while the rear image always ends up corrupt.

This is the existing code that retrieves the front .TIF file:

Dim fs As New FileStream(Me.FileName, FileMode.Open, FileAccess.Read)
Dim sr As New BinaryReader(fs)
Dim fname As String = {long formula to generate fname}

Dim fsFront As New FileStream(fname & "_Front.tif", FileMode.Create)
Dim swFront As New BinaryWriter(fsFront)
Dim imgBytesFront As Byte()

fs = New FileStream(Path.Combine(DownImageFiles, dr("ImgFile")), FileMode.Open, FileAccess.Read)
sr = New BinaryReader(fs)
imgBytesFront = sr.ReadBytes(dr("FrontLength"))

swFront.Write(imgBytesFront)
swFront.Close()
fsFront.Close()

I'm trying to add similar code to access the rear image file:

Dim fsRear As New FileStream(fname & "_Rear.tif", FileMode.Create)
Dim swRear As New BinaryWriter(fsRear)
Dim imgBytesRear As Byte()

fs = New FileStream(Path.Combine(DownImageFiles, dr("ImgFile")), FileMode.Open, FileAccess.Read)
Using br As New BinaryReader(fs)
    br.BaseStream.Seek(Long.Parse(dr("FrontLength"), Globalization.NumberStyles.Integer), SeekOrigin.Begin)
    imgBytesRear = br.ReadBytes(dr("RearLength"))
End Using

imgBytesRear = sr.ReadBytes(dr("RearLength"))
swRear.Write(imgBytesRear)
swRear.Close()
fsRear.Close()

This generates an image, but Windows says it is "damaged, corrupted, or is too large".

Any ideas what I'm missing? Am I using the Seek method properly? Am I somehow reading the first 6372 bytes again instead of skipping the first 10600 and starting there? Any help greatly appreciated!

Answer 1

Thanks to several people in the comments above, I found that simply loading the .IMG file in as a System.Drawing.Image, I could then split it into individual page files.

Dim tiffCheck As Image = Image.FromFile(Path.Combine(DownImageFiles, dr("ImgFile")))

After that, I essentially followed the solution under the Split() function here: https://code.msdn.microsoft.com/windowsdesktop/Split-multi-page-tiff-file-058050cc