[Fix] Fix bug in conversion of potsdam

[SBCV]

Motivation

Currently, the success of the conversion of the potsdam dataset depends on the order of the files returned by os.listdir(tmp_dir)[0]. This works correctly for the first zip file, but can potentially break the processing of the second zip file.

Modification

Ensure that a new temporary directory is created for each zip file. This way each temporary directory contains only one zip file. In this case os.listdir(tmp_dir)[0] will return the correct string.

[CLAassistant]

All committers have signed the CLA.

[Junjun2016]

Hi @SBCV
Thanks for your contribution.
Please sign the CLA.

[MengzhangLI]

Hi, thanks for your warm hearted pr.

By the way, in what circumstance would the potential error happen? In current code, all zip files are used in tempfile.TemporaryDirectory, which would be elapsed after all codes within it being executed.

Could you give certain examples or error snapshot to help me figure out your explanation? Thanks in advance.

Best,

[SBCV]

Let's assume that we have a folder containing

• 2_Ortho_RGB.zip
• 5_Labels_all_noBoundary.zip

Now let us assume that
zipp_list = glob.glob(os.path.join(dataset_path, '*.zip'))
contains
zipp_list = ["path/to/5_Labels_all_noBoundary.zip", "path/to/2_Ortho_RGB.zip"]

Note: The ORDER of zipp_list is ESSENTIAL for the bug to appear!

After the SECOND execution of

for zipp in zipp_list:
    zip_file = zipfile.ZipFile(zipp)
    zip_file.extractall(tmp_dir)

the temporary folder contains

2_Ortho_RGB	                             
	top_potsdam_2_10_RGB.tif          <-- these files are in a subfolder
	top_potsdam_2_10_RGB.tfw
	top_potsdam_2_11_RGB.tif
	top_potsdam_2_11_RGB.tfw
	...						
top_potsdam_2_10_label_noBoundary.tif     <-- these files are at the top level of the temp dir
top_potsdam_2_11_label_noBoundary.tif
....

Because the temporary folder already contains

top_potsdam_2_10_label_noBoundary.tif
top_potsdam_2_11_label_noBoundary.tif
...

the following if case (in the second iteration) is never executed

src_path_list = glob.glob(os.path.join(tmp_dir, '*.tif'))
if not len(src_path_list):

But it should, since the tif files in 2_Ortho_RGB.zip are located in a subdirectory.

Therefore, the created dataset directory does not contain the RGB images of the potsdam dataset (only the labels)

[MengzhangLI]

OK, got it. Thanks for your nice explanation!

[jason102811]

sbcv，您好！您在MMSeg项目中给我们提的PR非常重要，感谢您付出私人时间帮助改进开源项目，相信很多开发者会从你的PR中受益。
我们非常期待与您继续合作，OpenMMLab专门成立了贡献者组织MMSIG，为贡献者们提供开源证书、荣誉体系和专享好礼，可通过添加微信：openmmlabwx 联系我们（请备注mmsig+GitHub id），由衷希望您能加入！
Dear sbcv,
First of all, we want to express our gratitude for your significant PR in the MMSeg project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
We are looking forward to continuing our collaboration with you. OpenMMLab has established a special contributors' organization called MMSIG, which provides contributors with open-source certificates, a recognition system, and exclusive rewards. You can contact us by adding our WeChat（if you have WeChat): openmmlabwx, or join in our discord： https://discord.gg/qH9fysxPDW. We sincerely hope you will join us!
Best regards！ @SBCV