NSBitmapImageRep with double precision floats?

I have some processing code that works on double precision arrays that I'd like to visualize using an NSImage. I thought I could be clever and just use the NSBitmapImageRep data buffer directly, but it doesn't seem to support double precision values. I can get it to accept 32 bit floats, but not 64 bit doubles.

Now, I could keep a separate buffer of doubles, and then resize them all to floats for display but I'd like to find a better way.

I think the answer is a custom NSImageRep, but I'm having a hard time finding an example of one that draws bitmaps. In particular, how to implement the -draw method. Do I draw a colored rectangle for each pixel or is there a better way to transfer bitmap data?

Anybody have a better idea of how to do this?

 

Isn't -draw one of the methods in NSImageRep I need to implement?

The only references I've seen are in the Cocoa Drawing Guide:

And the NSImageRep Class Reference:

That doesn't sound like drawing rectangles, but I can't figure out which more primitive method to call from within my custom representation that I can give the NSCompositeCopy operator to.

 

I think you're getting at the first approach I listed-- keep a separate buffer of doubles and convert them through to a standard NSBitmapImageRep. I could, for example, create a CustomImageRep with an encapsulated NSBitmapImageRep, do a data conversion and transfer into that rep on each update, and then route the draw call to it. I'm not sure that's less naive though... For one thing I've now got two copies of each large data set hanging around.

How does NSBitmapImageRep do it's drawing? I'm sure it's not going straight to hardware, it must be using some Quartz calls, no? I mention drawing rectangles because I've seen that suggested in other places for transferring bitmap data-- I agree it feels a bit much, but when I think about what a bitmap really is it certainly isn't a sparse set of points-- it's an array of color patches.

Apple has intentionally not gone with the class cluster model on ImageReps to make it easier to subclass, so it seems like this is what they have in mind-- the only worked examples I can find though are vector formats.

 

Data sets can be of varying sizes, some much larger than a screen size.

I could certainly treat the data as a custom view and do all the windowing and whatnot that you're suggesting. It seems more natural to me, however, to treat it as an image. I agree it's odd that the -draw method is the base method to overload, rather than drawInRect: fromRect: operation: fraction: respectFlipped: hints:, but I'll have to see if overriding the later helps once I figure out how to override the former. I'm really not even to the point of optimizing yet, I'm just looking for where to start.

I feel like this is drifting away from my question: How do I implement the draw method of a custom NSImageRep representing a bitmap image?