Refactor:Improve the logic so that it does not decode base 64 for the test image each time (#9264)
### What problem does this PR solve?
Improve the logic so that it does not decode base 64 for the test image
each time
### Type of change
- [x] Refactoring
- [x] Performance Improvement
---------
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>
Refa: Update base64 test image with new sample data (#9115)
### What problem does this PR solve?
Replace the placeholder test image in base64_image.py with a new sample
image data string.
### Type of change
- [x] Refactoring