Re: scrolling images?

Re: scrolling images?

[Richard Stallman]

    The manual lacks info on working with images.  Maybe I'm wrong but I
    only see this section:

I don't think there is anything else a user can do with images.
Aside from that, there are only the facilities for programs.

    You cannot view all parts of an image which is larger than the frame
    (e.g. on an 800x600  display try
    http://www.ub.uni-bielefeld.de/diglib/adelung/grammati/1/jpeg/00000000.jpg
    -- scanned title page of a German dictionary (1808); I can send the
    image by mail if necessary).

I guess we need to have commands that can scroll through images.
Really C-v ought to do it.  This relates to one of the items
in etc/TO-DO.  Are you interested in working on it?

Re: scrolling images?

[Karl Eichwalder]

Richard Stallman <rms@gnu.org> writes:

> I don't think there is anything else a user can do with images.
> Aside from that, there are only the facilities for programs.

Thanks for telling me.

> I guess we need to have commands that can scroll through images.
> Really C-v ought to do it.  This relates to one of the items
> in etc/TO-DO.  Are you interested in working on it?

I fear that's too complicate for me.  I'll ask around on gnu.emacs.help;
maybe, somebody else already wrote appropriate commands.  Another
possibility could be to take over code pieces from Gnus' attachment
handling.

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Re: scrolling images?

[Karl Eichwalder]

Karl Eichwalder <keichwa@gmx.net> writes:

> Richard Stallman <rms@gnu.org> writes:

>> I guess we need to have commands that can scroll through images.
>> Really C-v ought to do it.  This relates to one of the items
>> in etc/TO-DO.

Concerning image handling items in the TODO file are rather sparse.

> I fear that's too complicate for me.  I'll ask around on gnu.emacs.help;
> maybe, somebody else already wrote appropriate commands.

Thus far nobody could offer help.

> Another possibility could be to take over code pieces from Gnus'
> attachment handling.

Gnus seems to lack the wanted features as well.

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Re: scrolling images?

[Glenn Morris]

Karl Eichwalder wrote:

> Karl Eichwalder <keichwa@gmx.net> writes:
>
>> Richard Stallman <rms@gnu.org> writes:
>
>>> I guess we need to have commands that can scroll through images.
>>> Really C-v ought to do it.  This relates to one of the items
>>> in etc/TO-DO.
>
> Concerning image handling items in the TODO file are rather sparse.
>
>> I fear that's too complicate for me.  I'll ask around on gnu.emacs.help;
>> maybe, somebody else already wrote appropriate commands.
>
> Thus far nobody could offer help.
>
>> Another possibility could be to take over code pieces from Gnus'
>> attachment handling.
>
> Gnus seems to lack the wanted features as well.

The Emacs mail client VM (http://www.wonderworks.com/vm/) divides images
into strips to allow scrolling. From the documentation of
vm-mime-use-image-strips:

    *Non-nil means chop an image into horizontal strip for display. Emacs
    treats a displayed image as a single large character and cannot scroll
    vertically within an image. To work around this limitation VM can
    display an image as a series of contiguous horizontal strips that
    Emacs' scrolling routines can better handle. To do this VM needs to
    have the ImageMagick programs 'convert' and 'identify' installed;
    `vm-imagemagick-convert-program' and `vm-imagemagick-identify-program
    must point to them.

    A nil value means VM should display images without cutting them into
    strips.

Does that sound like it would be of use?

Re: scrolling images?

[Stefan Monnier]

> The Emacs mail client VM (http://www.wonderworks.com/vm/) divides images
> into strips to allow scrolling. From the documentation of
> vm-mime-use-image-strips:
> 
>     *Non-nil means chop an image into horizontal strip for display. Emacs
>     treats a displayed image as a single large character and cannot scroll
>     vertically within an image. To work around this limitation VM can
>     display an image as a series of contiguous horizontal strips that
>     Emacs' scrolling routines can better handle. To do this VM needs to
>     have the ImageMagick programs 'convert' and 'identify' installed;
>     `vm-imagemagick-convert-program' and `vm-imagemagick-identify-program
>     must point to them.
> 
>     A nil value means VM should display images without cutting them into
>     strips.
> 
> Does that sound like it would be of use?

I think it's a neat workaround, but we want a real solution.
Emacs' display engine is quite capable of scrolling the image by bits,
the only problem is that the elisp scrolling commands work line-by-line.
Also a related problem is that elisp has no easy way to find the pixel-height
of a given line, so it's difficult from elisp to know how much to scroll.


	Stefan

Re: scrolling images?

[Richard Stallman]

    Also a related problem is that elisp has no easy way to find the pixel-height
    of a given line, so it's difficult from elisp to know how much to scroll.

I guess that primitive has to be the first job.

Re: scrolling images?

[Richard Stallman]

    The Emacs mail client VM (http://www.wonderworks.com/vm/) divides images
    into strips to allow scrolling. From the documentation of
    vm-mime-use-image-strips:

It would be very unclean to require every Lisp program that displays
images to cut them apart in this way in order to get better scrolling.
If it were installed inside of `create-image', and if all other Lisp
programs call `create-image', then the interface could remain clean.
That might be a good first step, I suppose.

Unfortunately we cannot use the code from VM, since its author
won't sign a copyright assignment.

What we really want in the longer term is to have scrolling commands
that do the job cleanly.

Scrolling images?

[Karl Eichwalder]

Problem:
========

You cannot view all parts of an image which is larger than the frame
(e.g. on an 800x600 display, try
http://www.ub.uni-bielefeld.de/diglib/adelung/grammati/1/jpeg/00000000.jpg
-- scanned title page of a German dictionary (1808).  You cannot scroll
right or down the image, neither using the mouse nor using the keyboard.

RMS confirmed the problem.  He asked whether I'd like help implementing
such a feature.  Ideally it should be bound to the regular scroll-up and
scroll-down command (C-v / M-v).  Unfortunately, that's too complicate
for me.

Has someone else already worked on this issue?

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ke@suse.de (work) / keichwa@gmx.net (home):              |
http://www.suse.de/~ke/                                  |      ,__o
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