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Reduce Tiff file size. Need to set bit dept to 1.

I want to reduce the image of a tiff by about 1/2.  Or maybe I just want to change the DPI from 300 to 96.  Either solution would be fine.  The method below takes a tiff and makes it larger because the bit depth changes from 1 to 32.  It does change the DBI from 300 to 96 and that is desirable.

I have read to use Imaging.PixelFormat.Format1bppIndexed in the constructor, but that creates the exception A Graphics object cannot be created from an image that has an indexed pixel format.

Thank you for your suggestions.


Method 1.
Public Sub ResizeAndSave03(ByVal ImagePath As String, ByVal SavePath As String)

        If File.Exists(SavePath) = True Then
            File.Delete(SavePath)
        End If

        Dim b As New Bitmap(ImagePath)
        Dim Width As Int32 = Convert.ToInt32(b.Width / 2)
        Dim Height As Int32 = Convert.ToInt32(b.Height / 2)
        Dim result As New Bitmap(Width, Height)
        Using g As Graphics = Graphics.FromImage(DirectCast(result, Image))
            'Will throw  - A Graphics object cannot be created from an image that has an indexed pixel format.
            'when this constructor used  Dim result As New Bitmap(Width, Height, Imaging.PixelFormat.Format1bppIndexed)
            g.DrawImage(b, 0, 0, Width, Height)
        End Using
        result.Save(SavePath)
    End Sub

Method 2.

 Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim inFile = "test01.tif"
        Dim outFile03 = "outFile03.tif"
        Dim thePath As String = Directory.GetParent(Directory.GetCurrentDirectory()).Parent.FullName + "\files\"
        Dim inImage As String = Path.Combine(thePath, inFile)
              ResizeAndSave03(inImage, Path.Combine(thePath, outFile03))

    End Sub
0
wilfordrocks
Asked:
wilfordrocks
  • 2
1 Solution
 
Joe Winograd, EE MVE 2015&2016DeveloperCommented:
My suggestion is to use IrfanView's command line capability. IrfanView is excellent (free!) imaging software that I've been using for many years:
http://www.irfanview.com/

I recommend the Brothersoft link to download IrfanView:
http://www.brothersoft.com/download-irfanview-6224.html

This will download a single install file called <iview437_setup.exe> with no adware and no junk!

And I recommend the Brothersoft link for the PlugIns, which are needed to give you PDF capability:
http://www.brothersoft.com/download-irfanview-all-plugins-164981.html

This will download a single install file called <irfanview_plugins_437_setup.exe> with no adware and no junk!

Install IrfanView first, then install the PlugIns. The PlugIns are optional...only if you want PDF support...and the other features that come with the PlugIns. Although I recommend adding the PlugIns, that's for general, future usage. For this situation, you don't need it, as IrfanView will handle your TIFF files directly.

The IrfanView command line options are documented in a file called <i_options.txt> in the installation folder. I have attached it to this post for your convenience for the latest version of IrfanView, 4.37. In terms of your goal to reduce size, note the following:

(1) The "/tifc" option, which sets the TIFF Compression. Values are:

0=None
1=LZW
2=Packbits
3=ITU-T Group 3
4=ITU-T Group 4
5=Huffman
6=JPG
7=ZIP

I've done a lot of experimenting with these settings and have found that 4 (ITU-T Group 4) provides the best compression in most cases.

(2) The "/dpi" option, which changes the DPI values.

(3) The "/bpp" option (bits per pixel), which changes the color depth.

If you'd like to see an IrfanView command line call (with TIFF Compression) used in a program, take a look at this article:
http://www.experts-exchange.com/Web_Development/Document_Imaging/A_10745-How-To-Combine-Merge-Append-TIFF-Files-in-Batch-Mode.html

Regards, Joe
IrfanView-4.37-i-options.txt
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wilfordrocksAuthor Commented:
Thank you for a very detailed response.
0
 
Joe Winograd, EE MVE 2015&2016DeveloperCommented:
You're welcome. Good luck with your project! Regards, Joe
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