Can not WindowLevel for some DICOM images

I'm using WindowLevel function to do w/l for dicom images, but i found that some of the images is not affected by this function, it just keep its original look however i do WindowLevel, this kind of image is very few, but i can not ignore them.
following is my code:

int nLUTLen = 256;//just for this image
RGBQUAD* pLUT = new RGBQUAD[nLUTLen];
//fill my pLUT, it assert valid
int nType = this->IsGrayScale(); //the return is 1
int nRes = WindowLevel(nLowBit, nHighBit, pLUT, nLUTLen, 1); //the return is 1

I'm using Leadtools 14.0 Medical Suite.
i tested this image with bin\DEMO32.exe, but the menu Color\Widow Level is gray.
the attachment is the image with problem.

Can anyone helps?
Thanks.

Thanks,

What does "The WinodwLevel function only works on 12 and 16 bit grayscale images." means exactly?
Does it means i'll can not apply WindowLevel to 8, 11, 13 or 14 bit grayscale images? if yes, how do i WindowLevel these kind of images?

Edited by moderator Tuesday, October 11, 2016 9:02:40 AM(UTC)  | Reason: Not specified

Due to a Microsoft Window's limitation on only being able to display 256 shades
of gray,WindowLeveling allows you toadjust which 256 shades of gray appear on
the screen at one time. So for 8 bit Grayscale images you do not need to
WindowLevel. For
11, 13 or 14 bit grayscale images, we do support these
bits per pixel, however, most images that are these bits per pixel are12 bit
allocated or 16 bit allocated. For instance you can have an image that is 12
bits allocated but only 10 of those 12 bits are used. This means the image is
10 bits per pixel but becausethere are 12 bits allocated for each pixel, it is
still considered a 12 bpp image. I hope these make this more clear for
you.

Edited by moderator Tuesday, October 11, 2016 9:03:01 AM(UTC)  | Reason: Not specified

Yes, i know what W/L just doing, i can display all the gray level of the 8 bit Grayscale images at one time, but some times, i would not like to show all the gray level, for instance, i just like to see the bone, assume the bone's gray level is between 200 - 255 for 8 bit unsigned image, then i just need map gray level 200 - 255 to display gray level(0 - 255), thus, i can get most contrast for only the bone region, of course, the gray level beyond 200 - 255 is invisible, but i don't need them this time, and next time, maybe i will like to see the soft tissue, this will need to map another gray level to display gray level.
So, WindowLevel for 8 bit grayscale images is senseful for medical image.

thx.

Edited by moderator Tuesday, October 11, 2016 9:03:25 AM(UTC)  | Reason: Not specified

Okay I see. We have a function called GetFunctionalLookupTable.
With this you can create your own LUT, specifiing a start and end
color. You would create a LUT, then alter the Bitmap's palette to
match the table.

Edited by moderator Tuesday, October 11, 2016 9:03:47 AM(UTC)  | Reason: Not specified