Format png file is bigger than original.

[wchaws]

IN: 1648891399391.png 389 kb
OUT: 5.98mb

  --> GET /1648891399391.png?x-oss-process=image/resize,w_1024,h_3949,m_fill/format,png/sharpen,100 200 574ms 5.98mb

Describe the bug

To Reproduce

Expected behavior

Please complete the following information about the solution:

• Version: [e.g. v1.0.0]
• Region: [e.g. us-east-1]
• Was the solution modified from the version published on this repository?
• If the answer to the previous question was yes, are the changes available on GitHub?
• Have you checked your service quotas for the sevices this solution uses?
• Were there any errors in the CloudWatch Logs?

Screenshots

Additional context