GNU bug report logs - #77841
Some svg image's black color is replaced by emacs's theme foreground color

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Alan Third <alan <at> idiocy.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#77841: closed (Some svg image's black color is replaced by
 emacs's theme foreground color)
Date: Thu, 10 Jul 2025 17:03:02 +0000

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Your message dated Thu, 10 Jul 2025 18:01:55 +0100
with message-id <aG_yAxbEBi2rbhTj <at> faroe.holly.idiocy.org>
and subject line Re: bug#77841: Some svg image's black color is replaced by emacs's theme foreground color
has caused the debbugs.gnu.org bug report #77841,
regarding Some svg image's black color is replaced by emacs's theme foreground color
to be marked as done.

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help-debbugs <at> gnu.org.)


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From: Billy Lei <LeiYiXia29 <at> outlook.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Some svg image's black color is replaced by emacs's theme foreground
 color
Date: Wed, 16 Apr 2025 20:09:46 +0800

I found this issue when debugging org LaTeX preview, see 
https://list.orgmode.org/87cydchjqn.fsf <at> gmail.com/T/#ed7ba8310f82e8be8a2e7360df1568ed485434df3

> When using themes with background color set to #000000, and org-preview-default-process is set to dvisvgm, the LaTeX fragments are displayed incorrectly.
> 
> To reduplicate:
> 
> 1. Switch to a theme with background color set to #000000 (like Modus Vivendi)
> 2. Set org-preview-default-latex-process to dvisvgm
> 3. Create an org-mode document. Write some LaTeX fragment and press C-c C-x C-l to preview LaTeX fragment.
> 4. The LaTeX preview is displayed as a white rectangle.
> 
> After debugging, I found that it is because dvisvgm omitts the default #000 color value when generating SVG file, and emacs has a unique way of displaying the SVG, which caused foreground color to be applied to it.
> 
> A solution is to change org-format-latex-options to use transparent background by default. I've attached this fix.

It turned out that emacs displays svg images differently compared to an 
image viewer. I can reduplicate this issue when I use emacs to view this 
svg image, which emacs replaces the image's black color with the current 
theme's foreground color:

https://commons.wikimedia.org/wiki/File:Flag_of_the_German_Democratic_Republic.svg

See also (Chinese): https://emacs-china.org/t/emacs-30-1-svg/29217

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From: Alan Third <alan <at> idiocy.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: yantar92 <at> posteo.net, 77841-done <at> debbugs.gnu.org, manuel <at> ledu-giraud.fr,
 LeiYiXia29 <at> outlook.com
Subject: Re: bug#77841: Some svg image's black color is replaced by emacs's
 theme foreground color
Date: Thu, 10 Jul 2025 18:01:55 +0100

On Thu, Jul 10, 2025 at 09:03:31AM +0300, Eli Zaretskii wrote:
> 
> > Am I good to go ahead and push this to master? It's currently in 4
> > separate commits.
> 
> Feel free, and thanks.

Done, thanks.
-- 
Alan Third

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