bug#13887: 24.3; doc-view will render blurry images when image-magick is available

[E Sabof]

This function gives the native pixel dimensions of an image:

(defun es-image-file-pixel-dimensions (file)

  (let* ((type (image-type file nil nil))

         (spec (list 'image :type type :file file)))

    (image-size spec t)))

When

(> (getf (cdr (doc-view-current-image)) :width)

   (car (es-image-file-pixel-dimensions 

         (getf (cdr (doc-view-current-image)) :file))))

there is quality loss.

What I don't want to see is margins having a different width - for the same reasons you wouldn't put a photograph in a frame in the top left corner. Ideally I'd also center vertically (should the image be shorter than the window) and add a window-configuration-change-hook (or there might be an appropriate display-spec), so it's always centered. Unfortunately no image-viewer that currently comes with emacs (image-mode ,doc-view-mode ,image-dired-display-image-mode) does this.

Evgeni

On Wed, Mar 6, 2013 at 1:01 PM, Tassilo Horn <tsdh@gnu.org> wrote:

E Sabof <esabof@gmail.com> writes:

> I've tried it, indeed it works much better. Might it be possible to
> store the the "native" size, and raise the resolution automatically
> when the zoom exceeds it?

Well, the resolution should be increased and the doc reconverted when
the up-scaled image becomes blurry.  But how should emacs know when you
think it becomes blurry?

> On a side note, might it be also possible to horizontally center the
> image?  There is a pretty straight-forward way to do it, used in the
> about-emacs screen.

I guess this could be done somehow.  But do you want to center to make
the contents a bit larger and not to see the margins?  If so, then
slicing to the bounding box (`s b') followed by fitting to width (`W')
may be the better approach.

Bye,
Tassilo