[Feature] Support qualitative comparison tools (#1303)

* Add base gui
* support patch compare
* support slider compare
* readme
* add recording prompt
* fix lint
* fix comments

Co-authored-by: unknown <zhangjingdong@pjlab.org>

tools/gui/README.md

@@ -0,0 +1,105 @@
+# MMEditing Viewer
+
+- [Introduction](#introduction)
+- [Major features](#major-features)
+- [Prerequisites](#prerequisites)
+- [Getting Started](#getting-started)
+- [Examples](#examples)
+- [Contributing](#contributing)
+
+## Introduction
+
+**MMEditing Viewer** is a qualitative comparison tools to facilitate your research.
+
+## Major features
+
+- **Patch-based comparison**
+  - Crop a patch on multiple images to compare
+  - Batch comparison
+  - Flexible settings on number of columns and size of images.
+  - Save your comparison result
+- **Before/After slider comparison**
+  - Support both videos and images comparison
+  - Record and save comparison results as a video clip
+
+## Prerequisites
+
+MMEditing Viewer works on Linux, Windows and macOS. It requires:
+
+- Python >= 3.6
+- PyQt5
+- opencv-python (headless version)
+
+## Getting Started
+
+**Step 0.**
+Install PyQt5.
+
+```shell
+pip install PyQt5
+```
+
+**Step 1.**
+Install and check opencv-python version.
+If your meet following errors:
+
+```
+QObject::moveToThread: Current thread is not the object's thread.
+Available platform plugins are: xcb... .
+```
+
+Please install opencv-python-headless version.
+
+```shell
+pip install opencv-python-headless
+```
+
+**Step 2.**
+Install MMEditing.
+
+```shell
+git clone -b 1.x https://github.com/open-mmlab/mmediting.git
+```
+
+If you want to follow the newest features, you can clone `dev-1.x` branch.
+
+```shell
+git clone -b dev-1.x https://github.com/open-mmlab/mmediting.git
+```
+
+**Step 3.**
+Run
+
+```shell
+python tools/gui/gui.py
+```
+
+## Examples
+
+**1. Patch-based comparison: batch images**
+
+https://user-images.githubusercontent.com/49083766/199232588-7a07a3d9-725d-48be-89bf-1ffb45bd5d74.mp4
+
+**2. Patch-based comparison: single image**
+
+https://user-images.githubusercontent.com/49083766/199232606-f8539191-4bda-4b2c-975a-59020927abae.mp4
+
+**3. Before/After slider comparison: images**
+
+https://user-images.githubusercontent.com/49083766/199232615-2c56dcf1-0b42-41a5-884c-16a8f28a2647.mp4
+
+**4. Before/After slider comparison: input video frames**
+
+https://user-images.githubusercontent.com/49083766/199232617-e03a06dc-727b-43bb-8110-049d0fff28ba.mp4
+
+**5. Before/After slider comparison: input Mp4 video**
+
+https://user-images.githubusercontent.com/49083766/199232651-87d8064e-cbaf-4d30-b90b-94ee0af7d497.mp4
+
+**6. Before/After slider comparison: record**
+
+https://user-images.githubusercontent.com/49083766/199232634-eca70d28-8437-400a-8ab9-d2fe396b6ea9.mp4
+
+## Contributing
+
+We appreciate all contributions to improve MMEditing Viewer. You can create your issue to report bugs or request new features. Welcome to give us suggestions or contribute your codes.