The reason why the image quality of quark network disk becomes low may be due to the use of compression algorithm. Files uploaded to the network disk can be compressed to reduce the file size, thus saving storage space and improving transmission speed. The compression algorithm will compress the file according to certain rules, including reducing the details and color depth of the image, which will lead to the decline of image quality.

When a user downloads a compressed file, Quark network disk will decompress the file and restore it to its original state, so the image quality of the downloaded file will not be affected. This is because the decompression process will restore the details and color depth after compression, thus restoring the original clarity and quality of the file.

It should be noted that the use of compression algorithm is to improve the efficiency in the process of storage and transmission, but it will also cause some loss to the image quality of the file. Therefore, when uploading important HD files, it is recommended to choose uncompressed storage mode to maintain the original image quality of the files.

In addition, there are some factors that may affect the change of image quality, such as packet loss during network transmission, network speed and other factors, which may lead to a slight difference between downloaded files and uploaded files. Therefore, in the process of network transmission, maintaining a stable network connection and high-speed download speed are also important factors to ensure the quality of file images.

To sum up, the image quality of Quark network disk becomes lower because the file is compressed when it is uploaded, but decompressed and restored when it is downloaded. At the same time, other factors in the process of network transmission may also have a slight impact on image quality.