c4e3c244ea
## 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**_
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