[O] Error with inline image resizing

[Takeshi Teshima]

Hi all,

When I try to show inline images automatically resized in an org-mode buffer, the thumbnail doesn't show (a big blank box shows where the resized image should be) and the following errors are echoed in the "*Messages*" buffer.

```

ImageMagick error: no decode delegate for this image format `JPEG' @ error/constitute.c/ReadImage/504

```

The image types I have tried are JPG and PNG.

When tried with a PNG file, the error message changes to 

```

ImageMagick error: no decode delegate for this image format `PNG' @ error/constitute.c/ReadImage/504

```

* [Related settings]:

** init.el

`(setq org-image-actual-width nil)`

** the org-mode file

```

#+ATTR_LATEX: :width 300pt

[[file:20160802-142357_2016-08-02_13.35.28-1.jpg]]

```

I tried this with Emacs running in the safe mode, i.e. running with "-q" option.

The inline image shows correctly (with the original size) until I set `org-image-actual-width` to `nil`, after which I don't see the image in the buffer

 (A big blank box appears where the image should be. I also see the errors mentioned above in the "*Messages*" buffer.).

* [Current workaround I use]:

It doesn't occur when I use the snippet in this SO answer.

http://stackoverflow.com/questions/17637685/configuring-emacs-for-showing-fixed-width-inline-images

It basically rewrites org-display-inline-images function.

* [Environmental information]:

** (i) I built my Emacs using the following tool:

https://github.com/renard/emacs-build-macosx

by running `./build-emacs emacs-24.5`.

It was built with ImageMagick, and I can correctly export LaTeX formula with it.

Also it works fine when I don't use the resize feature, i.e. `org-image-actual-width` is set to `t`.

** (ii) Versions

*** Emacs:  emacs-24.5.50.1

*** Mac OS X: El Capitan 10.11.6(15G31).

*** $ convert --version

Version: ImageMagick 6.9.5-1 Q16 x86_64 2016-07-15 http://www.imagemagick.org

Copyright: Copyright (C) 1999-2016 ImageMagick Studio LLC

License: http://www.imagemagick.org/script/license.php

Features: Cipher DPC Modules 

Delegates (built-in): bzlib freetype jng jpeg ltdl lzma png tiff webp xml zlib

Thank you very much in advance.

    diadochos