Re: ChannelThresholdImage interface

On Thu, 20 Mar 2003, Glenn Randers-Pehrson wrote:
> >
> >Does anyone have an idea of how the current syntax can be supported
> >while also being able to specify that a channel should not be altered?
>
> Two possibilities:  Use negative input for channels to be ignored,
> or define another input option -channel-select <mask>.  I think the
> original intent in ImageMagick was to do the latter, but it has not
> happened yet.  Channel selection is a little confusing because we need
> to consider CMYKA, in which the opacity channel is displaced into
> the index channel.

The negative input would work (as would any other invalid option such
as a character or empty argument), but adding a new command-line
option would not work since the function does its own parsing of the
argument.

We could support unspecified channel arguments like

  -threshold '30%//40%/'

to threshold only the red and blue channels.  Does that seem like a
good approach?

Bob
======================================
Bob Friesenhahn
[email protected]
http://www.simplesystems.org/users/bfriesen



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