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G'MIC Markdown

The main G'MIC documentation pages are written using a specific Markdown-like syntax, namely G'MIC Markdown (a.k.a gmd). You can contribute writing documentation pages with this syntax.

G'MIC Markdown is defined by these simple rules:

• Sections and subsections

Start a line with one, two, three or four consecutive number signs (#), then a whitespace, to begin a section, a sub-section, a sub-sub-section or a sub-sub-sub-section:

# 1. Section title
## 1.1. Sub-section title
### 1.1.1. Sub-sub-section title
#### 1.1.1.1. Sub-sub-sub-section title

is rendered as

1. Section title

1.1. Sub-section title

1.1.1. Sub-sub-section title

1.1.1.1. Sub-sub-sub-section title

• Lists:

Start a line with one of the characters *,-,+ or _ to insert a list item:

* First item
* Second item
- Indent with two whitespaces to start a sub-list.
+ Indent with four whitespaces to start a sub-sub-list.
* Third iterm

is rendered as

First item

Second item

Indent with two whitespaces to start a sub-list.

Indent with four whitespaces to start a sub-sub-list.

Third iterm

• Centered blocks:

A line that contains three consecutive equal signs === opens or closes a centered block:

===
This text is centered
===

is rendered as

This text is centered

• Right-aligned blocks:

A line that contains three consecutive greater-than signs >>> opens or closes a right-aligned block:

>>>
This text is right-aligned
>>>

is rendered as

This text is right-aligned

• Tables:

A line starting with |, ||, |- or |+ defines one row of a table.

is rendered as:

First Name	Last Name	Group
Angus	Young	AC/DC
Kirk	Hammett	Metallica
David	Gilmour	Pink Floyd

The first delimiter actually defines the border style:

|: No borders.

||: Vertical borders only.

|-: Horizontal borders only.

|+: Both horizontal and vertical borders.

• Blockquote:

A line starting with > defines a blockquote (possibly multi-line):

> \G'MIC is a full-featured open-source framework for digital image processing,
> distributed under the **CeCILL** free software licenses (**LGPL**-like and/or **GPL**-compatible).
>
> It provides several user interfaces to _convert / process / visualize_ generic images.

is rendered as

G'MIC is a full-featured open-source framework for digital image processing,
distributed under the CeCILL free software licenses (LGPL-like and/or GPL-compatible).

It provides several user interfaces to convert / process / visualize generic images.

• Detail block:

A line starting with three consecutive question mark (???) opens or closes a detail block that the user can open or close on demand.

??? Details:
There are the details you want!
???

is rendered as

Details:

There are the details you want!

• Code block:

A line that contains three consecutive backticks (```) or tildes (~~~) opens or closes a block of code:

~~~
1. This is a block of code.
2. It can have multiple lines.
~~~

is rendered as

1. This is a block of code.
2. It can have multiple lines.

• Shell command:

A line that contains three consecutive double quotes (""") opens or close a shell command block.
It displays what you gets in stderr and stdout when you run a command from the shell.

"""
gmic help index
"""

is rendered as

$ gmic help index

index (+):
{ [palette] | palette_name },0<=_dithering<=1,_map_colors={ 0:No | 1:Yes }

Index selected vector-valued images by specified vector-valued palette.
'palette_name' can be { default | hsv | lines | hot | cool | jet | flag | cube | rainbow | algae | amp |balance | curl | deep | delta | dense | diff | haline |
ice | matter | oxy | phase | rain | solar | speed | tarn |tempo | thermal | topo | turbid | aurora | hocuspocus | srb2 | uzebox }

Default values: 'dithering=0' and 'map_colors=0'.

Example:
[#1] image.jpg +index 1,1,1
[#2] image.jpg (0;255;255^0;128;255^0;0;255) +index[-2] [-1],1,1

Tutorial: https://gmic.eu/tutorial/gindex

• Horizontal rule:

A line that contains three consecutives minus signs (---) or underscores (___) or asterisks (***) inserts an horizontal rule.

---
***
___

is rendered as

• Text styles

Special separators can be used to enclose a word or a phrase to apply specific text styles:

This is ***bold and italic*** ⟶ This is bold and italic (colored version).

This is ___bold and italic___ ⟶ This is bold and italic.

This is **bold only** ⟶ This is bold only (colored version).

This is __bold only__ ⟶ This is bold only.

This is *italic only* ⟶ This is italic only (colored version).

This is _italic only_ ⟶ This is italic only.

This is ~~strikethrough~~ ⟶ This is strikethrough.

This is ==underlined== ⟶ This is underlined.

This is `in monospace` ⟶ This is in monospace.

This is { a set of values } ⟶ This is { a set of values }.

This is a highlighted monospace 'expression' ⟶ This is a highlighted monospace expression (works for expressions having up to two whitespaces).

• Links

There are three different ways of inserting a clickable link in a .gmd file:

Enclose the link between separators < and >, as <https://gmic.eu> ⟶ https://gmic.eu.

Enclose a text between two consecutive single quotes to link to:

A reference page, about a command: ''blur'' ⟶ blur.

A section in a reference page: ''Mathematical Expressions'' ⟶ Mathematical Expressions.

To force a hard link to a G'MIC reference page, add a minus sign - as first character of the link: ''-blur'' ⟶ blur.

Use the generic expression [This is a link](https://gmic.eu) ⟶ This is a link.

• Images

There are two different ways to insert an image in a .gmd file:

Use the expression

This is an image: ![gmicky the tiger](https://gmic.eu/img/gmicky_deevad220.jpg)

is rendered as

This is an image: gmicky the tiger

You can also directly invoke the G'MIC interpreter to generate an image:

This is a G'MIC-generated image: %% sp gmicky,220 deform 30 blur_radial 2% frame xy,1,0 %%

is rendered as

This is a G'MIC-generated image: sp gmicky,220 deform 30 blur_radial 2% frame xy,1,0

• Math Formula

If you have pdflatex installed on your system, you can insert LaTeX equations in your .gmd document:

$$ f(x) &= \cos\left(x + \frac{pi}{2}\right) \\
&= -\sin(x) $$

is rendered as

$f(x) &= \cos\left(x + \frac{\pi}{2}\right) \\ &= -\sin(x)$

• Anchor

Start a line with an equal sign (=), then a whitespace, to define an invisible anchor that can be used in links afterwards:

= document_top

Then, you can add an anchor link somewhere else:

[This is an anchor link](#document_top) ⟶ This is an anchor link

• Convert a .gmd file to HTML

Assuming you have gmic installed (the CLI interface of G'MIC), then the command below converts a file input.gmd into a HTML file output.html:

$ gmic it input.gmd gmd2html ot output.html

◀ Funny Oneliners | Help Writing Reference Documentation ▶

A Full-Featured Open-Source Framework for Image Processing

Latest stable version: 3.5.5 Current pre-release: 3.6.0 (2025/08/04)

G'MIC Markdown

• Sections and subsections

1. Section title

1.1. Sub-section title

1.1.1. Sub-sub-section title

1.1.1.1. Sub-sub-sub-section title

• Lists:

• Centered blocks:

• Right-aligned blocks:

• Tables:

• Blockquote:

• Detail block:

• Code block:

• Shell command:

• Horizontal rule:

• Text styles

• Links

• Images

• Math Formula

• Anchor

• Convert a .gmd file to HTML