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#1 Posted : Thursday, October 11, 2007 3:53:43 AM(UTC)

subo  
subo

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Hi,

I am wondering if predefined threshold value can be used as input to any contrast enhancement function in leadtools. For example, in my recent project I need to enahnce the contrast of images with predefined threshold values. For example, if I have an 8 bit image and if I calculate the threshold for signal and background as 200, then how can I pass this threshold information as an input to the leadtools function to enhance the contrast?

Awating for fruitful response...

Thanking you,
Subo
 

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#2 Posted : Thursday, October 11, 2007 11:41:13 AM(UTC)

jigar  
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Hello,

Our ChangeContrastCommand handles that for you, so there isn't an option to specify any values of that sort.  But you can use those values to determine what percentage value to pass to the method.  So for example if you have threshold value of 200, based on what that represents or means to you, you can set the contrast change value to 15%, -50%, etc.  Let me know if this answers your question.  What language/interface are you developing in?  Based on that I can give more specifics on the implementation of the change contrast command if you need.

Thanks.
 
#3 Posted : Thursday, October 11, 2007 8:11:29 PM(UTC)

subo  
subo

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Hi jigar,

Thanks for your reply. To be specific, I am using .Net C# for developing the application. I have a requirement "auto adjust contrast" for viewing purpose. This expects 80% of the pixels after contrast have a value of 0. So in such case how should I proceed to serve my purpose?

Thanking you,
Subo
 
#4 Posted : Friday, October 12, 2007 11:06:33 AM(UTC)

jigar  
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Hello,

So you are saying that you would like to adjust the contrast within a certain range?  I say "range" because there's no absolute value for a contrast.  Also what do you mean by "a value of 0".  You mean to say you want them to be black or you want that to be the center of the contrast range?  For example, if the contrast range was from 150 to 300, you would want 80% of the pixels to be at 225?
 
#5 Posted : Sunday, October 14, 2007 7:17:32 PM(UTC)

subo  
subo

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Hi,

Yes, you are right. I would like to have 80% of pixel as black after the contrast adjustment. I want this because in my application around 80% pixels are the background, which are darker in comparison to 20% of foreground pixels. I even know the threshold value, which is at a value around 200 in the range of 0 to 255. I mean foreground intensities are always more than 200 and background intensities are always less than 200. So, please let me know how background pixels can be made darken (black) using contrast adjustment in leadtools?

Thanking you,
Subo
 
#6 Posted : Tuesday, October 16, 2007 5:29:32 AM(UTC)

jigar  
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Hello Subo,

Since your images have a uniform contrast, all you need to do it figure out how much contrast you would need to increase on an image.  The ChangeContrastCommand has only one paramemter, which is the percentage of contrast increase/decrease.  Set it to 100 (10%) first, see how it looks, and just increment it by 100 each time until you get closer to your desired output.  Then you can do smaller increments/decrements to that value once you get closer, to find the best value.
 
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