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Re: Adjusting contrast levels for a batch of TIFF files

Posted by venukesireddy on May 20, 2008; 4:25pm
URL: http://imagej.273.s1.nabble.com/Adjusting-contrast-levels-for-a-batch-of-TIFF-files-tp3696177p3696179.html

hallo,

Many Thanks for your suggestions.( Now I understood why my images are Black in photoshop but bright in ImagJ. I have also got some advice from Christophe Leterrier, who suggested I import this batch of TIFF images and adjust brightness and contrast ( this requires 8 bit grayscale or RGB stack) so I am converting my RGB 16 bit images to 8 bit grayscale  and saving the images as Image sequence, so it works. This series of TIFF images are a result of a time lapse movie, so probably by loading movie it self and adjusting the contrast levels and saving as image sequence might also work.

many thanks for your suggestions.

Venu Kesireddy



--- On Tue, 5/20/08, Harry Parker <[hidden email]> wrote:

> From: Harry Parker <[hidden email]>
> Subject: Re: Adjusting contrast levels for a batch of TIFF files
> To: [hidden email]
> Date: Tuesday, May 20, 2008, 5:46 PM
> Hi Venu,
>
> I am not sure of what you want to do. One thing I've
> noticed for 16 bit images is that Photoshop expects white
> to be 2^16 - 1 = 65535 , while ImageJ looks at the
> distribution of values and displays the darkest as black
> and the lightest as white automatically. I'm assuming
> you have a similar problem.
>
> I had 10 bit linear images (max = 2^10-1=1023) saved in 16
> bit format. They looked good in ImageJ but black in
> Photoshop until I manually changed the contrast. By
> multiplying all the values in my images by 64, they looked
> good when opened in Photoshop. This is a single command in
> ImageJ ( menu: Process->Math->Multiply...->[type]
> 64.)
> Its very easy to apply the same processing to a whole
> folder of images. See the ImageJ documentation on
> "Virtual Stacks", or the example macros starting
> with "batch".
>
> If your images are linear in intensity, you will also want
> to adjust their "gamma" by some number around 0.5
> to brighten the middle gray values. (0.4545 is the standard
> value.) (Menu: Process->Math->Gamma...) This is
> required to compensate for the nonlinear intensity
> characteristics of computer displays. You may also want to
> first subtract some value from all your pixels if your
> darkest pixels look too light.
>  
> --
> Harry Parker
> Senior Systems Engineer
> Digital Imaging Systems, Inc.
>
>
> ----- Original Message ----
> From: kesireddy venu <[hidden email]>
> To: [hidden email]
> Sent: Tuesday, May 20, 2008 3:48:21 AM
> Subject: Adjusting contrast levels for a batch of TIFF
> files
>
> Dear list members ,
>
> I am looking for a simple way which can adjust the contrast
> levels of TIFF files  for a large batch of images.( Save
> those contast adjusted images) Opening each image and
> adjusting the contrast levels is very laborious work.
> Unfortunately other propritery software that I am using
> takes only contrast adjusted images. While Image J can
> display images of correct intensity automatically.The
> software I am using has no such option to adjust contrast
> levels.
> So are there any tricks to change contrast levels for a
> btach of TIFF files in photoshop or in ImageJ
>
> SINCERELY
> VENU