Re: False negatives with compare?

Thanks for you reply Fred.

I checked the 2 images, I still don't understand why just using "-alpha on" 
fails, based on the description of alpha on in the docs.

compare confuses me anyway, why does the order of the 2 images to compare 
matter?

Still on the 2 icons I referenced earlier, the last commands I was trying 
were:

compare -channel RGBA -alpha on -metric ae crushed.png original.png /dev/null
2 <- I expect 0 here, why is it 2?

compare -channel RGBA -alpha on -metric ae original.png crushed.png /dev/null
98 	<- wtf?


compare -channel RGBA -alpha set -metric ae crushed.png original.png /dev/null
0
compare -channel RGBA -alpha set -metric ae original.png crushed.png /dev/null
0


These last 2 look promising, but I don't trust that they do what I want for 
images that do contain an alpha.



I appreciate the one-liner replies but is there a place with more info for me 
to figure this out, please?

Thanks in advance,
Tim.



On 31 December 2009 am 11:38:28 Fred Weinhaus wrote:
> >Sorry I'm kind of new to this, how would I go about checking out the
> > actual structure of the first non-optimized image?
> 
> identify -verbose image.png