ereader_cover Directory Reference

Directory dependency graph for ereader_cover:

Directories
	inc
	scripts
	src

Detailed Description

The headline "show the book cover" pipeline, end to end (#143): pull the cover image out of an .epub, decode it, scale it to fit, and render it. The EPUB is opened in memory from a baked fixture (vendored miniz plus the bounded XML reader, zero-heap through a static arena); epub_get_cover_image resolves the properties="cover-image" manifest item; ra8_img_decode_blit decodes the PNG with stb_image, nearest-neighbour scales it preserving aspect ratio, and blits it into an RGB565 framebuffer – allocating only from a fixed SRAM bump arena, so the decode reaches no malloc (NASA Rule 3). The framebuffer is then hashed.

The fixture cover is a portrait at a real 2:3 book ratio, and the target box is landscape, so the fit is height-limited and the blitted image is narrower than the box. Its approved PNG bytes are embedded in the generator and every EPUB member is stored without compression, so regeneration does not depend on a host image encoder or compressor. No panel, SDRAM, touch or SD dependency.

It does not pass on silicon

On the bench epub_open fails outright on the real part, against the same baked in-memory fixture the host tests use. The UART reader was attached before the reset, so the #390 print-once race cannot explain it, and there is no SD card, external hardware or provisioning anywhere in this path – so it is a firmware defect, not a rig gap (#170). ra8_emulator cannot arbitrate it either: it stops on an Armv8.1-M encoding the Unicorn M33 model has no seam for. hil.conf holds the capture. Re-promote only from a bench capture showing the PASS banner and its CRC.

Why it exists separately

ereader_image (#106) and ereader_jpeg (#143) prove the bare decode + scale + blit pipeline for PNG and JPEG. This app adds the piece in front that the cover use case actually needs – pulling the image out of an EPUB manifest before decoding it. Any drift in EPUB cover resolution, the PNG decoder, the scale math or the toolchain trips the same deterministic hash gate.

Regenerate the fixture with examples/ek_ra8d2/hw_pending/ereader_cover/scripts/make_cover_fixture.py for src/main.c, then re-read the CRC the board prints and update hil.conf.