Original PickImageColors source-file lab, 2026-10-25.
Can an indexed PNG be transparent without an alpha band?
Run: python reproduce.py --case indexed-png-transparency --out rerun
Dependency: Pillow. Recorded runtime: Python 3.12.14, Pillow 12.3.0, libwebp 1.6.0.
Measurements are local source-file computations, not browser observations. Library-dependent compression sizes and quantizer choices may change with runtime.
We did not measure a browser color picker’s composited output. The fully transparent gold has stored RGB but contributes no visible foreground in an ordinary composite. This case concerns indexed palette transparency, not PNG quantization or unused palette entries.
