[Qgis-developer] Re: classification of rasters

[Peter Ersts]

Marco Hugentobler wrote:
> Hi Peter,
>
> You are right,  mValueClassification.size() should be replaced with 
> mCustomClassificationEnabled. My original idea was that it is either 
> clipping/stretching or custom colormap.
>   
Ok, great! I made this change already so it is currently either 
stretching or custom colormap and should behave when you switch between 
these options.

>> But I maintain the custom color map should display stretch values.
>>     
>
> I'm not sure I undestand what you mean. Do you mean that, if there is 
> stretching enabled and custom colormap, there should be a combination of 
> both?
> Maybe I can understand better with an example. Let's say we have a DTM and 
> there is clipping and stretching enabled for values 500 - 800. But in custom 
> colormap tab there are items 400 red / 600 green / 1000 blue and linear color 
> interpolation. How would the application behave in such a situation?

So yes, I am suggesting there should be a combination of both. In your 
example: the DTM values 500 - 800 get stretched from 0 to 255 for 
rendering. In this case the color map could also be scaled so that  0 = 
red 85= green and 255 = blue, but this is only done at during rendering, 
the table values still stay the same (i.e. 400 - 1000). It may not 
always make sense to do both but I am looking at if from a clarity and 
usability standpoint for the user. If it is only going to be one or the 
other, the we need to add quite a but more to the GUI to make it clear 
that the user that they only have one option or the other.

-pete

-- 
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Peter J. Ersts, Project Specialist
American Museum of Natural History
Center for Biodiversity and Conservation
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