[racket] Is there any way to get the bit depth of a bitmap?

Racket libraries can read and write images of various formats and
pixels depths, but a `bitmap%` object always represents an image using
1 or 32 bits per pixel in memory.

At Mon, 29 Sep 2014 23:14:43 +0800, rrandom wrote:
> Hi,I am recently working in the book Digital Image Processing with
> racket. I want to know is there any way to get the bit depth or color
> depth of a input bitmap in Racket? I found the get-depth method in
> racket/draw,bitmap%, but it only return 1 and 32, that's not what i
> really want.I input a bitmap whose bit depth is 8 but i got 32.
> following is the code:
> 
> > (send (read-bitmap "Fig0305(a)(DFT_no_log).tif")
> get-depth)
> 32
> 
> Is there anything I am wrong? Thank you!
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