0bc6747483
## Summary - EPUB books with PNG cover images now display covers on the home screen instead of blank rectangles - Adds `PngToBmpConverter` library mirroring the existing `JpegToBmpConverter` pattern - Uses miniz (already in the project) for streaming zlib decompression of PNG IDAT data - Supports all PNG color types (Grayscale, RGB, RGBA, Palette, Gray+Alpha) - Optimized for ESP32-C3: batch grayscale conversion, 2KB read buffer, same area-averaging scaling and Atkinson dithering as the JPEG path ## Changes - **New:** `lib/PngToBmpConverter/PngToBmpConverter.h` — Public API matching JpegToBmpConverter's interface - **New:** `lib/PngToBmpConverter/PngToBmpConverter.cpp` — Streaming PNG decoder + BMP converter - **Modified:** `lib/Epub/Epub.cpp` — Added `.png` handling in `generateCoverBmp()` and `generateThumbBmp()` ## Test plan - [x] Tested with EPUB files using PNG covers — covers appear correctly on home screen - [ ] Verify with various PNG color types (most stock EPUBs use 8-bit RGB) - [ ] Confirm no regressions with JPEG cover EPUBs <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit **New Features** - Added PNG format support for EPUB cover and thumbnail images. PNG files are automatically processed and cached alongside existing supported formats. This enhancement enables users to leverage PNG cover artwork when generating EPUB files, improving workflow flexibility and compatibility with common image sources. <!-- end of auto-generated comment: release notes by coderabbit.ai --> --------- Co-authored-by: Nik Outchcunis <outchy@gmail.com> Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Dave Allie <dave@daveallie.com>
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