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Re: Several suggestions for image support

From: Kim F. Storm
Subject: Re: Several suggestions for image support
Date: 21 Apr 2004 12:10:08 +0200
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3.50

David Kastrup <address@hidden> writes:

> address@hidden (Kim F. Storm) writes:
> > David Kastrup <address@hidden> writes:
> > 
> > > PNG images support transparency.  Emacs can't make use of it.  You can
> > > only have Emacs declare a particular color as transparent.  This is
> > > dissatisfactory.  It should tell the PNG decoding routines Emacs'
> > > background color for the purpose of transparency.
> > > 
> > > I would find it important if an image specifier could restrict the
> > > displayed portion of an image.
> > 
> > I have just implemented image slicing via a new slice property:
> > 
> >         display ((slice X Y WIDTH HEIGHT) (image ...))
> Does that imply that slicing is not only applicable to images?

Currently it only applies to images.  It can be extended to other
objects as well, but I don't plan to do that myself.

> Anyway, I have been wondering about how to make slicing an image
> property while being able to reuse the image for several slices.
> Making this a separate property of course solves that concern.
> The effect would presumably be that only the selected slice of the
> image gets displayed, right?  


>                               And if the current line height exceeds
> that of slices in consecutive rows, then there would be white space
> between them, right?  

Unfortunately, yes.

However, I have fixed the treatment of newline characters
so that non-empty lines are no longer made a minimum
height equal to the frame default line height.

So you can use very small slices with good results.

>                       Does anybody know offhand whether one can
> _reduce_ the linespacing to "tight" for a given interval?

We can probably build on the existing "overlapping rows" code,
thus allowing a slice to be physically higher than its logical
height.  But it is a bit complicated, so I postponed that to
later -- and to see if something better could be found.

> It probably will not be "crucial" though.


Kim F. Storm <address@hidden> http://www.cua.dk

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