[Numpy-discussion] first recarray steps

Vincent Schut schut@sarvision...
Wed May 21 01:48:25 CDT 2008


Christopher Barker wrote:
> 
> Vincent Schut wrote:
>> Lets say I have a rgb image of arbitrary size, as a normal ndarray 
>> (that's what my image reading lib gives me). Thus shape is 
>> (3,ysize,xsize), dtype = int8. How would I convert/view this as a 
>> recarray of shape (ysize, xsize) with the first dimension split up into 
>> 'r', 'g', 'b' fields? No need for 'x' and 'y' fields.
> 
> Take a look in this list for a thread entitled "recarray fun" about a 
> month ago -- you'll find some more discussion of approaches.

Well, actually that thread was my inspiration to take a closer look into 
recarrays...
> 
> Also, if you image data is rgb, usually, that's a (width, height, 3) 
> array: rgbrgbrgbrgb... in memory. If you have a (3, width, height) 
> array, then that's rrrrrrr....gggggggg......bbbbbbbb. Some image libs 
> may give you that, I'm not sure.

My data is. In fact, this is a simplification of my situation; I'm 
processing satellite data, which usually has more (and other) bands than 
just rgb. But the data is definitely in shape (bands, y, x).
> 
> Also, you probably want a uint8 dtype, giving you 0-255 for each byte.

Same story. In fact, in this case it's int16, but can actually be any 
data type, even floats, even complex.
But thanks for the thoughts :-)
> 
> -Chris
> 
> 
> 



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