Re: image-rotate: Accept angle as an argument

[Tino Calancha <tino.calancha@gmail.com>]

On Mon, 5 Sep 2016, Lars Ingebrigtsen wrote:

> Anyway, I don't really see the use case here: The only reason somebody
> (in real life) has for changing the displayed angle of an image is if
> it's vertical instead of horizontal (and vice versa), so rotating by 90
> degrees is the only thing that makes sense, I think.
>
> Do you see a use case for changing the displayed angle of an image by 72
> degrees?
I think not, but unfortunately i am not the right person to answer: i 
don't like photograpy.
You are right, these commands are fine.
OTOH, I read at the first line of the file that image.el is the image API: 
Why don't we provide a function 'image--change-orientation' and use it
in the 'image-rotate' implementation? (See patch below)
The new function playing similar role as 'image--change-size' in 
'image-increase-size'.
Then, users will keep using the same commands, but programs might
use 'image--change-orientation' if they need it.
This came to my mind after looking image-mode.el:
i guess the code in image-mode.el for the rotations/resizes would be
much simple using the API from image.el.

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commit e4621bb833ba0bf6b1d62800c1d03137458bc58e
Author: Tino Calancha <tino.calancha@gmail.com>
Date:   Tue Sep 6 01:24:05 2016 +0900

     Extract function from image-rotate accepting arbitrary angles

     * lisp/image.el (image--change-orientation): New defun.
     (image-rotate): Use it.

diff --git a/lisp/image.el b/lisp/image.el
index e1f52de..780305e 100644
--- a/lisp/image.el
+++ b/lisp/image.el
@@ -1011,9 +1011,12 @@ image--current-scaling
  (defun image-rotate ()
    "Rotate the image under point by 90 degrees clockwise."
    (interactive)
+  (image--change-orientation 90))
+
+(defun image--change-orientation (angle)
    (let ((image (image--get-imagemagick-and-warn)))
      (plist-put (cdr image) :rotation
-               (float (mod (+ (or (plist-get (cdr image) :rotation) 0) 90)
+               (float (mod (+ (or (plist-get (cdr image) :rotation) 0) angle)
                             ;; We don't want to exceed 360 degrees
                             ;; rotation, because it's not seen as valid
                             ;; in exif data.
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Repository revision: 62e4dc4660cb3b29cfffcad0639e51c7f382ced8