- Add 1-bit BMP generation with Atkinson dithering for better quality thumbnails
- Replace noise dithering with error diffusion for smoother gradients
- Add fillPolygon() to GfxRenderer for proper bookmark ribbon shape
- Change bookmark from rect+triangle carve to pentagon polygon
- Fix bookmark inversion when Continue Reading card is selected
- Show selection state on first render (not just after navigation)
- Fix 1-bit BMP palette lookup in Bitmap::readRow()
- Add drawBitmap1Bit() optimized path for 1-bit BMPs
The 1-bit format eliminates gray passes on home screen for faster rendering
while Atkinson dithering maintains good image quality through error diffusion.
Display book cover image as background in the Continue Reading card on
the home screen, improving visual identification of the current book.
Key changes:
- Add thumbnail generation (thumb.bmp) for EPUB and XTC/XTCH files
- Uses same dithering/scaling algorithms as sleep screen covers
- Target size: 240x400 (half screen) for optimal Continue Reading card fit
- Add JpegToBmpConverter::jpegFileToBmpStreamWithSize() for custom target sizes
- Add GfxRenderer::copyStoredBwBuffer() and freeStoredBwBuffer() for
framebuffer caching to maintain fast navigation performance
- Add UTF-8 safe string truncation for Korean/CJK text in title/author display
- Draw white boxes behind title/author text for readability over cover image
- Increase HomeActivityTask stack size to 4096 for cover image rendering
- Add bounds checking in XTC thumbnail generation to prevent buffer overflow
## Summary
* Swap to updated SDCardManager which uses SdFat
* Add exFAT support
* Swap to using FsFile everywhere
* Use newly exposed `SdMan` macro to get to static instance of
SDCardManager
* Move a bunch of FsHelpers up to SDCardManager
## Summary
* **What is the goal of this PR?**
Replace simple threshold-based grayscale quantization with ordered
dithering using a 4x4 Bayer matrix. This eliminates color banding
artifacts and produces smoother gradients on e-ink display.
* **What changes are included?**
- Add 4x4 Bayer dithering matrix for 16-level threshold patterns
- Modify `grayscaleTo2Bit()` function to accept pixel coordinates and
apply position-based dithering
- Replace simple `grayscale >> 6` threshold with ordered dithering
algorithm that produces smoother gradients
## Additional Context
* Bayer matrix approach: The 4x4 Bayer matrix creates a repeating
pattern that distributes quantization error spatially, effectively
simulating 16 levels of gray using only 4 actual color levels (black,
dark gray, light gray, white).
* Cache invalidation: Existing cached `cover.bmp` files will need to be
deleted to see the improved rendering, as the converter only runs when
the cache is missing.
## Summary
- Add basic JPG image support
- Map JPG back to 2-bit BMP output
- Can be used to later render the BMP file from disk or directly pass to
output if wanted
- Give the 3 passes over the data needed to render grayscale content,
putting it on disk is preferred to outputting it multiple times
## Additional Context
- WIP, looking forward to BMP support from
https://github.com/daveallie/crosspoint-reader/pull/16
- Addresses some of #11
