diff --git a/.readthedocs.yml b/.readthedocs.yml
deleted file mode 100644
index 25b0eb6..0000000
--- a/.readthedocs.yml
+++ /dev/null
@@ -1,35 +0,0 @@
-# Read the Docs configuration file for Sphinx projects
-# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
-
-# Required
-version: 2
-
-# Set the OS, Python version and other tools you might need
-build:
-  os: ubuntu-22.04
-  tools:
-    python: "3.11"
-    # You can also specify other tool versions:
-    # nodejs: "20"
-    # rust: "1.70"
-    # golang: "1.20"
-
-# Build documentation in the "docs/" directory with Sphinx
-sphinx:
-  configuration: docs/source/conf.py
-  # You can configure Sphinx to use a different builder, for instance use the dirhtml builder for simpler URLs
-  # builder: "dirhtml"
-  # Fail on all warnings to avoid broken references
-  # fail_on_warning: true
-
-# Optionally build your docs in additional formats such as PDF and ePub
-# formats:
-#    - pdf
-#    - epub
-
-# Optional but recommended, declare the Python requirements required
-# to build your documentation
-# See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
-python:
-   install:
-   - requirements: docs/requirements.txt
diff --git a/docs/.gitignore b/docs/.gitignore
deleted file mode 100644
index 9ab870d..0000000
--- a/docs/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-generated/
diff --git a/docs/Makefile b/docs/Makefile
deleted file mode 100644
index 02344e0..0000000
--- a/docs/Makefile
+++ /dev/null
@@ -1,23 +0,0 @@
-# Minimal makefile for Sphinx documentation
-#
-
-# You can set these variables from the command line.
-SPHINXOPTS    =
-SPHINXBUILD   = sphinx-build
-SOURCEDIR     = source
-BUILDDIR      = build
-
-# Put it first so that "make" without argument is like "make help".
-help:
-	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
-
-.PHONY: help Makefile
-
-clean:
-	rm -rf $(BUILDDIR)/*
-	find source -type d -name generated -print0 | xargs -0 rm -rf
-
-# Catch-all target: route all unknown targets to Sphinx using the new
-# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
-%: Makefile
-	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
diff --git a/docs/requirements.txt b/docs/requirements.txt
deleted file mode 100644
index 5183539..0000000
--- a/docs/requirements.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-..
-sphinx
-sphinx_automodapi
-sphinx_rtd_theme
diff --git a/docs/rtd_conda.yml b/docs/rtd_conda.yml
deleted file mode 100644
index af872e1..0000000
--- a/docs/rtd_conda.yml
+++ /dev/null
@@ -1,5 +0,0 @@
-# Conda environment definition to build documentation on RTD
-
-name: imgviz-docs
-dependencies:
-  - python=3
diff --git a/docs/source/_docstring_check.py b/docs/source/_docstring_check.py
deleted file mode 100644
index c88e4e7..0000000
--- a/docs/source/_docstring_check.py
+++ /dev/null
@@ -1,90 +0,0 @@
-import math
-
-
-def check(app, what, name, obj, options, lines):
-    ctx = DocstringCheckContext(app, what, name, obj, options, lines)
-
-    if what in ('function', 'method'):
-        _docstring_check_returns_indent(ctx)
-
-
-class DocstringCheckContext(object):
-    def __init__(self, app, what, name, obj, options, lines):
-        self.app = app
-        self.what = what
-        self.name = name
-        self.obj = obj
-        self.options = options
-        self.lines = lines
-
-        self.iline = 0
-
-    def nextline(self):
-        if self.iline >= len(self.lines):
-            raise StopIteration
-        line = self.lines[self.iline]
-        self.iline += 1
-        return line
-
-    def error(self, msg, include_line=True, include_source=True):
-        lines = self.lines
-        iline = self.iline - 1
-        msg = ('{}\n\n'
-               'on {}'.format(msg, self.name))
-
-        if include_line and 0 <= iline < len(lines):
-            line = lines[iline]
-            msg += '\n' + 'at line {}: "{}"\n'.format(iline, line)
-
-        if include_source:
-            msg += '\n'
-            msg += 'docstring:\n'
-            digits = int(math.floor(math.log10(len(lines)))) + 1
-            linum_fmt = '{{:0{}d}} '.format(digits)
-            for i, line in enumerate(lines):
-                msg += linum_fmt.format(i) + line + '\n'
-        raise InvalidDocstringError(msg, self, iline)
-
-
-class InvalidDocstringError(Exception):
-    def __init__(self, msg, ctx, iline):
-        super(InvalidDocstringError, self).__init__(self, msg)
-        self.msg = msg
-        self.ctx = ctx
-        self.iline = iline
-
-    def __str__(self):
-        return self.msg
-
-
-def _docstring_check_returns_indent(ctx):
-    # Seek the :returns: header
-    try:
-        line = ctx.nextline()
-        while line != ':returns:':
-            line = ctx.nextline()
-    except StopIteration:
-        return  # No `Returns` section
-
-    # Skip empty lines and seek the first line of the content
-    try:
-        line = ctx.nextline()
-        while not line:
-            line = ctx.nextline()
-    except StopIteration:
-        ctx.error('`Returns` section has no content')
-
-    # Find the indentation of the first line
-    # (note: line should have at least one non-space character)
-    nindent = next(i for i, c in enumerate(line) if c != ' ')
-
-    # Check the indentation of the following lines
-    try:
-        line = ctx.nextline()
-        while line.startswith(' '):
-            if (not line.startswith(' ' * nindent) or
-                    line[nindent:].startswith(' ')):
-                ctx.error('Invalid indentation of `Returns` section')
-            line = ctx.nextline()
-    except StopIteration:
-        pass
diff --git a/docs/source/_static/getting_started.jpg b/docs/source/_static/getting_started.jpg
deleted file mode 120000
index a607aed..0000000
--- a/docs/source/_static/getting_started.jpg
+++ /dev/null
@@ -1 +0,0 @@
-../../../.readme/getting_started.jpg
\ No newline at end of file
diff --git a/docs/source/_static/getting_started.py b/docs/source/_static/getting_started.py
deleted file mode 120000
index 9d0d294..0000000
--- a/docs/source/_static/getting_started.py
+++ /dev/null
@@ -1 +0,0 @@
-../../../getting_started.py
\ No newline at end of file
diff --git a/docs/source/conf.py b/docs/source/conf.py
deleted file mode 100644
index 98ff799..0000000
--- a/docs/source/conf.py
+++ /dev/null
@@ -1,314 +0,0 @@
-# -*- coding: utf-8 -*-
-#
-# Configuration file for the Sphinx documentation builder.
-#
-# This file does only contain a selection of the most common options. For a
-# full list see the documentation:
-# http://www.sphinx-doc.org/en/master/config
-
-# -- Path setup --------------------------------------------------------------
-
-# If extensions (or modules to document with autodoc) are in another directory,
-# add these directories to sys.path here. If the directory is relative to the
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-#
-import inspect
-import os
-import sys
-
-import pkg_resources
-import sphinx_rtd_theme
-
-sys.path.insert(0, os.path.abspath(os.path.dirname(__file__)))  # NOQA
-
-import _docstring_check
-
-__version__ = pkg_resources.get_distribution('imgviz').version
-on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
-tag = 'main'
-
-# -- Project information -----------------------------------------------------
-
-project = u'imgviz'
-copyright = '2019, Kentaro Wada'
-author = 'Kentaro Wada'
-
-# The short X.Y version
-version = __version__
-# The full version, including alpha/beta/rc tags
-release = __version__
-
-
-# -- General configuration ---------------------------------------------------
-
-# If your documentation needs a minimal Sphinx version, state it here.
-#
-# needs_sphinx = '1.0'
-
-# Add any Sphinx extension module names here, as strings. They can be
-# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
-# ones.
-extensions = [
-    'sphinx.ext.autodoc',
-    'sphinx.ext.autosummary',
-    'sphinx.ext.coverage',
-    'sphinx.ext.githubpages',
-    'sphinx.ext.intersphinx',
-    'sphinx.ext.napoleon',
-    'sphinx.ext.linkcode',
-    'sphinx.ext.mathjax',
-]
-
-# Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
-
-# The suffix(es) of source filenames.
-# You can specify multiple suffix as a list of string:
-#
-# source_suffix = ['.rst', '.md']
-source_suffix = '.rst'
-
-# The master toctree document.
-master_doc = 'index'
-
-# The language for content autogenerated by Sphinx. Refer to documentation
-# for a list of supported languages.
-#
-# This is also used if you do content translation via gettext catalogs.
-# Usually you set "language" from the command line for these cases.
-language = None
-
-# List of patterns, relative to source directory, that match files and
-# directories to ignore when looking for source files.
-# This pattern also affects html_static_path and html_extra_path.
-exclude_patterns = []
-
-# The name of the Pygments (syntax highlighting) style to use.
-pygments_style = None
-
-
-# -- Options for HTML output -------------------------------------------------
-
-# The theme to use for HTML and HTML Help pages.  See the documentation for
-# a list of builtin themes.
-#
-# html_theme = 'alabaster'
-html_theme = 'sphinx_rtd_theme'
-html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
-
-# Theme options are theme-specific and customize the look and feel of a theme
-# further.  For a list of options available for each theme, see the
-# documentation.
-#
-# html_theme_options = {}
-
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
-
-# Custom sidebar templates, must be a dictionary that maps document names
-# to template names.
-#
-# The default sidebars (for documents that don't match any pattern) are
-# defined by theme itself.  Builtin themes are using these templates by
-# default: ``['localtoc.html', 'relations.html', 'sourcelink.html',
-# 'searchbox.html']``.
-#
-# html_sidebars = {}
-
-
-# -- Options for HTMLHelp output ---------------------------------------------
-
-# Output file base name for HTML help builder.
-htmlhelp_basename = 'imgvizdoc'
-
-
-# -- Options for LaTeX output ------------------------------------------------
-
-latex_elements = {
-    # The paper size ('letterpaper' or 'a4paper').
-    #
-    # 'papersize': 'letterpaper',
-
-    # The font size ('10pt', '11pt' or '12pt').
-    #
-    # 'pointsize': '10pt',
-
-    # Additional stuff for the LaTeX preamble.
-    #
-    # 'preamble': '',
-
-    # Latex figure (float) alignment
-    #
-    # 'figure_align': 'htbp',
-}
-
-# Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title,
-#  author, documentclass [howto, manual, or own class]).
-latex_documents = [
-    (master_doc, 'imgviz.tex', u'imgviz Documentation',
-     u'Matthew Matl', 'manual'),
-]
-
-
-# -- Options for manual page output ------------------------------------------
-
-# One entry per manual page. List of tuples
-# (source start file, name, description, authors, manual section).
-man_pages = [
-    (master_doc, 'imgviz', u'imgviz Documentation', [author], 1)
-]
-
-
-# -- Options for Texinfo output ----------------------------------------------
-
-# Grouping the document tree into Texinfo files. List of tuples
-# (source start file, target name, title, author,
-#  dir menu entry, description, category)
-texinfo_documents = [
-    (master_doc, 'imgviz', u'imgviz Documentation',
-     author, 'imgviz', 'One line description of project.',
-     'Miscellaneous'),
-]
-
-
-# -- Options for Epub output -------------------------------------------------
-
-# Bibliographic Dublin Core info.
-epub_title = project
-
-# The unique identifier of the text. This can be a ISBN number
-# or the project homepage.
-#
-# epub_identifier = ''
-
-# A unique identification for the text.
-#
-# epub_uid = ''
-
-# A list of files that should not be packed into the epub file.
-epub_exclude_files = ['search.html']
-
-
-# -- Extension configuration -------------------------------------------------
-
-# -- Options for intersphinx extension ---------------------------------------
-
-# Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {
-    'python': ('https://docs.python.org/3/', None),
-    'numpy': ('https://docs.scipy.org/doc/numpy/', None),
-}
-
-# Autosummary fix
-autosummary_generate = True
-
-# Try to suppress multiple-definition warnings by always taking the shorter
-# path when two or more paths have the same base module
-
-
-def setup(app):
-    app.connect('autodoc-process-docstring', _autodoc_process_docstring)
-
-
-def _autodoc_process_docstring(app, what, name, obj, options, lines):
-    _docstring_check.check(app, what, name, obj, options, lines)
-
-
-def _import_object_from_name(module_name, fullname):
-    obj = sys.modules.get(module_name)
-    if obj is None:
-        return None
-    for comp in fullname.split('.'):
-        obj = getattr(obj, comp)
-    return obj
-
-
-def _is_egg_directory(path):
-    return (path.endswith('.egg') and
-            os.path.isdir(os.path.join(path, 'EGG-INFO')))
-
-
-def _is_git_root(path):
-    return os.path.isdir(os.path.join(path, '.git'))
-
-
-_source_root = None
-
-
-def _find_source_root(source_abs_path):
-    # Note that READTHEDOCS* environment variable cannot be used, because they
-    # are not set under docker environment.
-    global _source_root
-    if _source_root is None:
-        dir = os.path.dirname(source_abs_path)
-        while True:
-            if _is_egg_directory(dir) or _is_git_root(dir):
-                # Reached the root directory
-                _source_root = dir
-                break
-
-            dir_ = os.path.dirname(dir)
-            if len(dir_) == len(dir):
-                raise RuntimeError('Couldn\'t parse root directory from '
-                                   'source file: {}'.format(source_abs_path))
-            dir = dir_
-    return _source_root
-
-
-def _get_source_relative_path(source_abs_path):
-    return os.path.relpath(source_abs_path, _find_source_root(source_abs_path))
-
-
-def _get_sourcefile_and_linenumber(obj):
-    # Retrieve the original function wrapped by contextlib.contextmanager
-    if callable(obj):
-        closure = getattr(obj, '__closure__', None)
-        if closure is not None:
-            obj = closure[0].cell_contents
-
-    # Get the source file name and line number at which obj is defined.
-    try:
-        filename = inspect.getsourcefile(obj)
-    except TypeError:
-        # obj is not a module, class, function, ..etc.
-        return None, None
-
-    # inspect can return None for cython objects
-    if filename is None:
-        return None, None
-
-    # Get the source line number
-    _, linenum = inspect.getsourcelines(obj)
-
-    return filename, linenum
-
-
-def linkcode_resolve(domain, info):
-    if domain != 'py' or not info['module']:
-        return None
-    if 1 == int(os.environ.get('IMGVIZ_DOCS_SKIP_LINKCODE', 0)):
-        return None
-
-    # Import the object from module path
-    obj = _import_object_from_name(info['module'], info['fullname'])
-
-    # If it's not defined in the internal module, return None.
-    mod = inspect.getmodule(obj)
-    if mod is None:
-        return None
-    if not (mod.__name__ == 'imgviz' or mod.__name__.startswith('imgviz.')):
-        return None
-
-    # Retrieve source file name and line number
-    filename, linenum = _get_sourcefile_and_linenumber(obj)
-    if filename is None or linenum is None:
-        return None
-
-    filename = os.path.realpath(filename)
-    relpath = _get_source_relative_path(filename)
-
-    return 'https://github.com/wkentaro/imgviz/blob/{}/{}#L{}'.format(
-        tag, relpath, linenum)
diff --git a/docs/source/getting_started.rst b/docs/source/getting_started.rst
deleted file mode 100644
index 4252dc9..0000000
--- a/docs/source/getting_started.rst
+++ /dev/null
@@ -1,7 +0,0 @@
-Getting Started
----------------
-
-.. image:: /_static/getting_started.jpg
-   :align: center
-
-.. literalinclude:: /_static/getting_started.py
diff --git a/docs/source/index.rst b/docs/source/index.rst
deleted file mode 100644
index 15f7040..0000000
--- a/docs/source/index.rst
+++ /dev/null
@@ -1,25 +0,0 @@
-.. _root:
-
-imgviz Documentation
-====================
-
-Image Visualization Tools.
-
-.. image:: /_static/getting_started.jpg
-   :align: center
-
-.. include:: installation.rst
-
-.. toctree::
-   :maxdepth: 2
-
-   getting_started.rst
-   Examples <https://github.com/wkentaro/imgviz/tree/main/examples>
-   reference/index.rst
-
-
-Indices and tables
-==================
-
-* :ref:`genindex`
-* :ref:`search`
diff --git a/docs/source/installation.rst b/docs/source/installation.rst
deleted file mode 100644
index 085bafd..0000000
--- a/docs/source/installation.rst
+++ /dev/null
@@ -1,9 +0,0 @@
-Installation
-------------
-
-.. code-block:: bash
-
-   pip install imgviz
-
-   # there are optional dependencies like skimage, below installs all.
-   pip install imgviz[all]
diff --git a/docs/source/reference/classes/index.rst b/docs/source/reference/classes/index.rst
deleted file mode 100644
index b302311..0000000
--- a/docs/source/reference/classes/index.rst
+++ /dev/null
@@ -1,9 +0,0 @@
-Classes
-=======
-
-.. autosummary::
-   :toctree: generated/
-   :nosignatures:
-
-   imgviz.Depth2RGB
-   imgviz.Nchannel2RGB
diff --git a/docs/source/reference/draw/index.rst b/docs/source/reference/draw/index.rst
deleted file mode 100644
index 2c77027..0000000
--- a/docs/source/reference/draw/index.rst
+++ /dev/null
@@ -1,14 +0,0 @@
-Draw Module
-===========
-
-.. autosummary::
-   :toctree: generated/
-   :nosignatures:
-
-   imgviz.draw.circle
-   imgviz.draw.rectangle
-   imgviz.draw.star
-   imgviz.draw.text
-   imgviz.draw.text_in_rectangle
-   imgviz.draw.text_size
-   imgviz.draw.triangle
diff --git a/docs/source/reference/functions/index.rst b/docs/source/reference/functions/index.rst
deleted file mode 100644
index 35b3667..0000000
--- a/docs/source/reference/functions/index.rst
+++ /dev/null
@@ -1,26 +0,0 @@
-Functions
-=========
-
-.. autosummary::
-   :toctree: generated/
-   :nosignatures:
-
-   imgviz.asgray
-   imgviz.gray2rgb
-   imgviz.rgb2gray
-   imgviz.rgb2rgba
-   imgviz.rgb2hsv
-   imgviz.rgba2rgb
-   imgviz.hsv2rgb
-   imgviz.depth2rgb
-   imgviz.flow2rgb
-   imgviz.instances2rgb
-   imgviz.label_colormap
-   imgviz.label2rgb
-   imgviz.nchannel2rgb
-   imgviz.plot_trajectory
-
-   imgviz.centerize
-   imgviz.normalize
-   imgviz.resize
-   imgviz.tile
diff --git a/docs/source/reference/index.rst b/docs/source/reference/index.rst
deleted file mode 100644
index 2ee76e0..0000000
--- a/docs/source/reference/index.rst
+++ /dev/null
@@ -1,12 +0,0 @@
-.. _reference:
-
-API Reference
-=============
-
-.. toctree::
-   :maxdepth: 2
-
-   functions/index.rst
-   classes/index.rst
-   draw/index.rst
-   io/index.rst
diff --git a/docs/source/reference/io/index.rst b/docs/source/reference/io/index.rst
deleted file mode 100644
index 2d7ade6..0000000
--- a/docs/source/reference/io/index.rst
+++ /dev/null
@@ -1,15 +0,0 @@
-IO Module
-=========
-
-.. autosummary::
-   :toctree: generated/
-   :nosignatures:
-
-   imgviz.io.imread
-   imgviz.io.imsave
-   imgviz.io.cv_imshow
-   imgviz.io.cv_waitkey
-   imgviz.io.pyplot_to_numpy
-   imgviz.io.pyglet_imshow
-   imgviz.io.pyglet_run
-   imgviz.io.PygletThreadedImageViewer