imread (repost)

[Daniel J Sebald]

soren at hauberg.org wrote:
> Quoting Daniel J Sebald <daniel.sebald at ieee.org>:
> 
>> soren at hauberg.org wrote:
>>
>>> Quoting Daniel J Sebald <daniel.sebald at ieee.org>:
>>>
>>>> 100% transparent would be not visible, I guess.  The applications   
>>>> would be special effects or masking off a rectangular image to  
>>>> make  it appear of a different shape.
>>>
>>>
>>>
>>> But what does 'not visible' mean? Should we just show the  
>>> background  color of the figure?
>>
>>
>> Yes, whatever is behind the image (up to the point of plotting the  
>> image) gets blended with the image.  Wherever the image is 100%  
>> transparent the contents behind it is completely visible, i.e.,  
>> unaltered.
> 
> 
> Currently (and also in matlab I believe) you can only view one image  at 
> a time.

That is why I'm not necessarily in the match-Matlab-exactly camp.  (However, can't multiple images be placed by using a collection of subplots?  Of course, that doesn't mean Matlab has implement alpha-blending across subplots.)

Anyway, I don't think there is any reason to not handle the data for a fourth dimension in terms of imread()/imshow().  There still may be image processing applications that want to simply bring in the image, perhaps manipulate the alpha channel in some way, and then send the whole image to file as a new image.  No need for imshow() for that.

Dan