RE: [Matplotlib-users] sending plot output to a bitmap widget

[Perry G. <pe...@st...>]

John Hunter wrote:

> Well, assuming you passed it to matplotlib with no colormap, then a
> default intensity grayscale would be used.  In that case, just build
> the rgb array as above using string methods and then take the r, g, or
> b slice out of it since they are all identical.
> 
Yep, this is the simple case.

> If you passed in a colormap, you would need to invert the colormap,
> which would be relatively easy to provide in the colors.Colormap
> interface but I'm having trouble imagining why someone would want to
> do this.
> 
Me too.  (Well, I'm thinking of older displays that actually 
used color lookup tables. The image would be stored in the 
display buffer as 8-bit intensity, and displayed to the screen
through a lookup color table. In that case one could manipulate
the image display as a intensity image and expect to read it 
out as such while using whatever psychedelic color table one wanted
to please their eyes. But that's rare these days.)

> Both of these would be lossy, of course, eg if you started with an
> array of floats you would get back an array of UInt8s.
> 
Yep.

> Note agg comes with several helpful pixel converters functions: gray8,
> rgb565, rgb555, bgr24, bgr24, bgra32, abgr32, argb32, rgba32.  Perhaps
> the best general solution is to define these as module constants and
> provide a single tostring method that takes one of these constants and
> returns the appropriate string representation.  I can image that this
> would be useful both for backend agg and the image module.
> 
Sounds reasonable.

Perry