ImagePro>Re: median filter and floating point images

[Aryeh Weiss <aryeh[at]optics.jct.ac.il>]

On Monday 07 July 2003 05:50 pm, Martin, Jean-Paul wrote:
> My un-educated guess is that somewhere in the process of filtering a
> floating point image, some of the filters used in IPP don't support the
> floating point format, forcing IPP to convert the data to 8-bit by default.
> The data is filtered and then it's converted back to floating point.
>
> If that's the case, I suggest doing all the pre-filtering in 12 bit or 16
> bit format and convert to float when you start doing the arithmetical
> stuff.
>
 I was afraid this was the case. Perhaps it would not be too hard to make the 
internal conversion be by default to 16 bits. In some cases, it is awkward to 
work with 12 or 16 bit formats when the highest value is 1023. I can scale 
the images with no loss, but since I have to take ratios, it is easier to 
convert to floating point and work in that format. 

Perhaps it woudl not be too difficult to change the default internal 
conversions to 16 bit.

One other thing that affects floating point images. The binary logical 
functions (AND, OR, etc) are not able to work with floating point format.
This is no surprise -- a bitwise comparison would make no sense. However, it 
would be nice if there were a "logical" or "binary" file type that could be 
used for conveniently running masks on floating point images. Presently, I 
use the "MIN" function against my mask, and I also MAX against 0 to eliminate 
negative values. But this means that I have to make sure that my mask has 
values greater than anything in the floating point image, and this is not 
always assured.

--aryeh



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