### 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

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Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### 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

### What problem does this PR solve?

#9050

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)