Re: image size limit?

[Chong Yidong <cyd@stupidchicken.com>]

David Kastrup <dak@gnu.org> writes:

>> But it definitely sounds better to scale according to display size
>> rather than frame size (but round up to minimum size e.g. 4096x4096).
>
> It sounds to me like the limits should be configurable, with a
> somewhat conservative default.  Applications where larger dimensions
> might be appropriate (image viewers with provisions for panning, i.e.)
> can allow them in their own buffers using buffer-local settings of the
> variables limiting the size.

Scaling according to display size isn't entirely problem-free either,
because Emacs frames can be put on different X displays ;-)

I think scaling according to frame size is not a great solution, but
it's OK because of the way image loading works.  If the frame is
initially too small, Emacs won't load the image.  But each time you
increase the size of the frame, Emacs checks again, and loads the
image if the size relative to the frame is now OK.  Once an image is
loaded, it's put in the image cache, so it will always be displayed
regardless of the frame size.

The max-image-size code is checked into CVS.  I've set a conservative
value of 6.0 times the frame width and height.  After all, the
original rationale for this feature is to avoid over-allocating memory
in case a malicious image demands a gigantic image widths/heights of
millions of pixels.  In ordinary situations, it shouldn't get in the
way of the user.