Re: importing functions from image package to core

[Daniel J Sebald]

On 10/15/2012 02:01 PM, John W. Eaton wrote:
> On 15-Oct-2012, Carnë Draug wrote:
>
> | Hi
> |
> | there's a bunch of simple functions on the image package that I think
> | could be moved to octave core (even though they used to belong to the
> | matlab image processing toolbox). These are the isbw, isgray, isind
> | and isrgb.
> |
> | The reason I propose the move is that some functions in core already
> | perform this checks but have their own code.
>
> Which functions do that?
>
> | This functions are very
> | simple and would cause very little maintenance issues while reducing
> | repeated code.
> |
> | If no one objects, I can prepare a changeset with them.
> |
> | By the way, matlab removed this functions because of
> | 
> http://blogs.mathworks.com/steve/2007/03/09/what-happened-to-isgray-isind-isbw-and-isrgb/
> | Not sure about the best approach there.
>
> It seems like these functions are not really very useful.  So why
> should we have them?  I'd vote for deprecating them instead of moving
> them to core Octave.

Deprecate.  As Carnë stated, these routines are very short, typically on 
the order of a couple conditional statements.  So if the user really 
wants to implement the functionality of one of these, it's not a challenge.

The problem with these routines is that they impose a meaning on the 
data that simply can't be done generally.  For example, "isbw" really 
means "is-the-data-0-or-1-only".  Similarly "isrbg" really means 
"is-the-data-MxNx3".  Etc.

If you feel these routines are often used and have general use, I'd 
propose coming up with different names that reflect what the routine is 
specifically testing.  It seems to me the scenario is if the user loads 
an image (or data), not quite sure if it is 1 component, or 3 
components.  Otherwise, the user sort of needs to know the nature of the 
data before hand, i.e., black and white image, monochrome image, etc. 
If the data originates from some known image encoding standard, such 
information should be available from the encoding header.

Dan