On Tue, Aug 10, 2010 at 4:21 PM, Eric Firing <efir...@hawaii.edu> wrote:
> On 08/10/2010 10:27 AM, Friedrich Romstedt wrote: > > Ah, the list config got me ... (resending to list) > > > > 2010/8/10 Benjamin Root<ben.r...@ou.edu>: > >> I am working on a function that can take a Colormap object and return a > >> grayscale form of it. Ideally, I would like to return the same type of > >> Colormap that was provided, but I am wondering if this is necessary. I > >> supposed it is sufficient to just create a LinearSegmentedColormap from > the > >> self._lut data? > >> > >> The problem I see with that approach is that there is still possibly > some > >> information loss, particularly with the alpha part of the rgba data. > >> LinearSegmentedColormap has a .from_list() function, but it uses only > the > >> rgb part of the rgba array and does not take alpha data. > >> > >> Is the inability of setting alpha a problem? Or maybe I should use > >> deepcopy() instead? > > > > If you mean me, I really don't know, but I think it is always better > > to do things > > properly than to publish something done with the attitute "just > > working" .... > > > > So I think it is probably best to code it into the Colormap object > > itself, so that each and ever derived class can define its own method > > of how to create a greyscale version. What do you think about that? > > Good idea. The base class could define a default to_grayscale() method > that would do the conversion near the very end of the Colormap.__call__ > method if an as_gray attribute, also defined in the base class, is True. > No need for getters and setters--let it be a simple attribute. This > is much simpler than generating a whole new colormap--instead, just set > an attribute to switch an existing colormap to gray or back to color. I > would leave the switch out of the __init__ args and kwargs. If someone > wants grey, they can add one more line of code to set the attribute. I > suspect only a small fraction of users will need this. > > If people really are going to want to fiddle with the conversion > function, then the scheme above could easily be extended by allowing the > as_gray attribute to be a callable; if it is a callable, then > to_grayscale() would use it instead of the default function. > > Eric > > > > > Friedrich > > > > Interesting ideas, I will try that out tonight. Ben Root
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