bug#54493: 27.2; image-convert :data broken

bug#54493: 27.2; image-convert :data broken

[awrhygty]

I tried to view non-native image files.
I need not only to set variables, but also to modify a function.
The externally converted data is broken by automatic code-conversion.

(setq image-use-external-converter t
      image-converter--converters
      '((imagemagick :command ("magick" "convert")
                     :probe ("-list" "format"))))
(advice-add #'image-converter--convert
            :before (lambda (&rest r) (setq-local coding-system-for-read 'binary)))



In GNU Emacs 27.2 (build 1, x86_64-w64-mingw32)
 of 2021-03-26 built on CIRROCUMULUS
Repository revision: deef5efafb70f4b171265b896505b92b6eef24e6
Repository branch: HEAD
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Pro (v10.0.2009.19044.1586)

Recent messages:

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY W32NOTIFY ACL GNUTLS LIBXML2
HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS MODULES THREADS JSON PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: JPN
  locale-coding-system: cp932

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
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  font-lock-mode: t
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  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

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emacs)

Memory information:
((conses 16 48618 9086)
 (symbols 48 6089 1)
 (strings 32 16924 1180)
 (string-bytes 1 521726)
 (vectors 16 9935)
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 (floats 8 21 347)
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 (buffers 1000 11))

bug#54493: 27.2; image-convert :data broken

[Lars Ingebrigtsen]

awrhygty@outlook.com writes:

> I tried to view non-native image files.
> I need not only to set variables, but also to modify a function.
> The externally converted data is broken by automatic code-conversion.

I can reproduce this in Emacs 27.2, but not on the trunk, so it looks
like this has been fixed.  Here's my test case:

(insert-image
 (create-image
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (insert-file-contents "/home/larsi/src/WebKit/LayoutTests/fast/css/resources/bikes.bmp")
    (buffer-string))
  nil t :format 'image/bmp))



-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#54493: 27.2; image-convert :data broken

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Mon, 21 Mar 2022 17:35:07 +0100
> Cc: 54493@debbugs.gnu.org
> 
> awrhygty@outlook.com writes:
> 
> > I tried to view non-native image files.
> > I need not only to set variables, but also to modify a function.
> > The externally converted data is broken by automatic code-conversion.
> 
> I can reproduce this in Emacs 27.2, but not on the trunk, so it looks
> like this has been fixed.  Here's my test case:
> 
> (insert-image
>  (create-image
>   (with-temp-buffer
>     (set-buffer-multibyte nil)
>     (insert-file-contents "/home/larsi/src/WebKit/LayoutTests/fast/css/resources/bikes.bmp")
>     (buffer-string))
>   nil t :format 'image/bmp))

What if you evaluate this first:

  (set-default-coding-systems 'utf-8-dos)

Does it still work for you?  The OP is on MS-Windows, where the
default decodes the CRFL EOLs, something we shouldn't do with image
data.

In general, I believe explicitly binding coding-system-for-read, as
the OP suggested, is better than relying on some code somewhere that
just happens to let this work (on some systems).

bug#54493: 27.2; image-convert :data broken

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> What if you evaluate this first:
>
>   (set-default-coding-systems 'utf-8-dos)
>
> Does it still work for you?

Yes.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no