feat: render .clip thumbnails.

[Sola-ris]

Summary

Add support for rendering .clip thumbnails.
Fixes #1146

.clip project files embedd an SQLite database at the end of the file which contains the thumbnail in the CanvasPreview table.

Before

After

Sources for the file format

• clip-studio-paint-layers-extractor
• The test file opened in a text editor

File used for testing

Drawing by Surendra Rajawat hosted on Clip Studio Paint's website

Tasks Completed

• Platforms Tested:
  • Windows x86
  • Windows ARM
  • macOS x86
  • macOS ARM
  • Linux x86
  • Linux ARM
• Tested For:
  • Basic functionality
  • PyInstaller executable

[Pheubel]

I just tried this PR on windows 10 (x86_64) with a simple illustration i quickly drew together and an illustration that uses a newer version of CSP and it works like expected, this will be a nice addition for my artist friend. 👍

[TrigamDev]

Checked and it appears to be working as expected

[CyanVoxel]

Sorry for the delay on reviewing this! Everything looks great outside of the hanging sqlite connection to the .clip file. I know it's been a while since you've submitted this PR, and I'd be more than happy to implement the change on your behalf if you don't have the time to.

[Sola-ris]

Sorry for the delay on reviewing this! Everything looks great outside of the hanging sqlite connection to the .clip file. I know it's been a while since you've submitted this PR, and I'd be more than happy to implement the change on your behalf if you don't have the time to.

No worries^^

I'm kinda surprised about the indent on conn.close(). It works, but I would have expected that it should be part of the with block.

[CyanVoxel]

Thank you for your work on this, and the quick update!