## Summary
Consolidate the script help/startup fixes so standalone helper commands
can show usage without requiring runtime-only dependencies or generating
files.
## Details
Several helper scripts imported optional packages, evaluated newer
annotations, or started generation before users could inspect CLI usage.
On a fresh checkout, this made common help paths fail on missing
packages such as `cairosvg`, `Pillow`, `freetype-py`, `fontTools`,
`pyphen`, `pyserial`, or on Python 3.9 annotation evaluation. A few
generators also treated `--help` as a normal output argument and wrote
files instead of printing usage.
This change keeps runtime dependencies on the code paths that need them,
handles lightweight help/list commands first, and adds explicit `--help`
handling for generator scripts that previously started work.
## Validation
- `python3 <script> --help` across tracked Python scripts, excluding
`scripts/patch_jpegdec.py` because it is a PlatformIO pre-build hook
rather than a standalone CLI
- `python3 scripts/convert_icon.py` still exits with usage for missing
required arguments
- `python3 lib/EpdFont/scripts/fontconvert_sdcard.py --list-presets`
- `python3 -m py_compile` for the changed scripts
## Summary
* What is the goal of this PR?
- Allow users to create custom sleep screen images with standard tools
(ImageMagick, GIMP, etc.) that render cleanly on the e-ink display
without dithering artifacts. Previously, avoiding dithering required
non-standard 2-bit BMPs that no standard image editor can produce. ( see
issue #931 )
* What changes are included?
- Add 4-bit BMP format support to Bitmap.cpp (standard format, widely
supported by image tools)
- Auto-detect "native palette" images: if a BMP has ≤4 palette entries
and all luminances map within ±21 of the display's native gray levels
(0, 85, 170, 255), skip dithering entirely and direct-map pixels
- Clarify pixel processing strategy with three distinct paths:
error-diffusion dithering, simple quantization, or direct mapping
- Add scripts/generate_test_bmps.py for generating test images across
all supported BMP formats
## Additional Context
* The e-ink display has 4 native gray levels. When a BMP already uses
exactly those levels, dithering adds noise to what should be clean
output. The native palette detection uses a ±21 tolerance (~10%) to
handle slight rounding from color space conversions in image tools.
Users can now create a 4-color grayscale BMP with (imagemagic example):
```
convert input.png -colorspace Gray -colors 4 -depth
```
---
### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _** YES**_
Danila Yudin