accessing bitmap representation, NSImage

[Riccardo Mottola]

Hi,

trying to debug certain stuff in PRICE, I found out that a certain 
assumption I made is perhaps not true or only conditionally true. I'm 
investigating on Mac 10.4, not yet on GNUstep, so this is not a bug, I 
ask what to do best.

In PRICE all filters need to access the "raw data", that is, they 
manipulates pixesl directly or even their components. To do that, I need 
to access the data in  the NSBitmapImageRep.

NSImages are allocated in the standard way, by opening TIFFS or jpegs.

What I always did is get the first representation of the representation. 
It has always been an NSBitmaImageRep and it is very fast, it is already 
there.
I had the suspect that this assumption was fragile and only found in 
quick examples, although it always worked for TIFF or JPEGS or PNGs.

However I have a consistent way of proving it wrong: Open a 16bit depth 
image on Mac. Be it grayscale or RGB. What happens is:
- after loading I have an NSimage, with a single 16-bit depth bitmap rep 
with either 1 or 3 samples (that is, 16bit or 48bit)
- as soon as i want tor un the filter, the only representation present 
is a CachedImageRep, which is unsuitable for my purpose, it is the image 
used for rendering to the screen. Pixel size changed and most notably, 
it is an 8bit image, it can even be a color image instead of a grayscale 
image

I understand I can have more representations, I expected to find BOTH 
the cached representation but also he original image. How can I get the 
original image data, as I had after opening the file? Instead I end 
having only the screen representation, this confuses me.

Perhaps by playing with the cache use options?

Riccardo