README_en.md · 空间栈/GRAS数据处理

# GRAS-data-processing

## Description
The project provides the capability to process data provided by Lunar and Planet Exploration Program Ground Application System (GRAS) of Chinese Lunar Exploration Program (CLEP). The data can be downloaded from Lunar and Planetary Data Release System website ([https://clpds.bao.ac.cn](https://clpds.bao.ac.cn)).

## Architecture
The project employes Python 3.11. To allow people with limited coding experience to try the tool, the project only needs basic commands to operate in order to reduce the reliance on IDEs or other frameworks.

## Installation

1.  Install Python v3.11
2.  Use command `pip install [package_name]` to install the following packages:
* pds4-tools
* Pillow
* scikit-image
* colour-science
* matplotlib
* colour-demosaicing
* tqdm
3.  Download or Git clone this repository to arbitary location where Python is allowed to run.

## Instructions

### Scope of Use
As of now, this repo is mainly used to offer image export functions that convert raw data obtained from GRAS to common image formats. The major sources of such type of data include *Chang'e*-3/4/5 lander, *Yutu*-1/2 rover and *Zhurong* rover.

GRAS website allows users to download data and label files in PDS4 format. The file extensions of data files are usually .2A, .2B and .2C as the extensions of label files are .2AL, .2BL and .2CL. Under normal circumstances, the parsing and exporting of data require the existence of both data and corresponding label files. But in special cases, data processing can be done by feeding minimal data required without original label files, as described in the following section.

### Label File Generation (optional)
As of now, due to unknown reasons, the GRAS website is unable to provide download service for part of the label files, which mostly are from the Tianwen-1 mission. While waiting for a fix of the issue, users can use the script *CreateLabelFile.py* to generate temporary label files by using templates to enable partial data parsing.

The scientific payloads currently supported by this method include *Zhurong* rover's Navigation and Terrain Camera (NaTeCam) and Multispectral Camera (MSCam), whose label file templates are placed under *.\template* directory in this repo.

**Usage**
```
python .\src\CreateLabelFile.py -i input_dir -t template_file
```

**Options**

`-i` (required) The directory where data files are stored.

`-t` (required) The path of the label file templates.

Suppose we have data file named *HX1-Ro_GRAS_NaTeCamB-sample.2C* under directory *.\TW1*. An example of the running of the script is:

```
python .\src\CreateLabelFile.py -i .\TW1\ -t .\template\template-NaTeCam.2CL
```

Once executed, the script will generated a temporary label file called *HX1-Ro_GRAS_NaTeCamB-sample-temp.2CL* within the input directory. If there is already a label file with standard file namen under that directory, the script won't perform an action.

The user can run the script repeatedly by feeding different templates against the same directory. The script will examine each data file to determine whether to apply the current template automatically.

There are two different formats of the Multispectral Camera (MSCam) data files, the sizes of which are 128 KB and 8192 KB respectively. Templates with corresponding names will be applied accordingly.

**Note: The generated temporary data files do NOT guaranteed to fully work as expected. Please use the standard label file offered by the official source when possible.**

### Image Export

This script implements image export of data with valid label file to common image formats.

**Usage**
```
python .\src\ExportImage.py -i input_dir [-o output_dir] [-f format] [--no-debayer] [--no-stretch]
```
**Options**

`-i` (required) The directory where data and label files are stored. Mixture of different types of data is allowed as the script is capable of selecting suitable export methods automatically.

`-o` (optional) The direcotry where exported images are to be stored. Input directory will be selected if omitted.

`-f` (optional) Format of exported images. JPG and PNG are two available options as JPG being the default one.

`--no-debayer` (optional) By default, the script will go through the debayer process to generate a color image. Applying this option will disable this particular step. Additionally, the script will automatically skip the debayer process if the file to be process is a panchromatic image, thus the user doesn't have to enable this option deliberately.

`--no-stretch` (optional) By default, the script will perform a 2% linear stretch to achieve better contrast. Enabling this option will skip the stretch and generate images based on original brightness data.

### Rename Image by Timestamp (optional)

By default, when sorted by file names, the order of data and output image files do not represent the order of time when the images were taken, which brings difficulty for those who wish for a sort-by-date function. This script reads the timestamp embedded within the original image file name and adds it at the beginning of the original one, enabling a convenient sort-by-date capability.

**Usage**
```
python .\src\RenameImageByTime.py -i input_dir
```

**Options**

`-i` (required) The directory where image files are stored. Only files with .jpg and .png extensions will be renamed.

Suppose there's file
```
HX1-Ro_GRAS_NaTeCamB-F-004_SCI_N_20210705045826_20210705045826_00051_A.jpg
```
By running the script against the directory where it is located, its file name becomes:
```
20210705045826_HX1-Ro_GRAS_NaTeCamB-F-004_SCI_N_20210705045826_20210705045826_00051_A.jpg
```

## Reference

This project along with its partial codes is based on the work [用Python打开嫦娥玉兔的科学数据](http://siyu.china-vo.org/2019/02/11/MakingOfCE4Image/?continueFlag=55e456ec3bc9bcf0d27e8ecc80f8e10d) and Github repo [ChangE_4_data_playground](https://github.com/siyu6974/ChangE_4_data_playground).

Special thanks to the author [Siyu Zhang](http://siyu.china-vo.org/).

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Author Sina Weibo：空间栈

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