LiteReader

Light e-reader for old Android devices ( minimum deployment : Android 4 "Ice cream sandwich" , API 14. . APK about 3.5 MB, no network access, only READ_EXTERNAL_STORAGE. Everything below was measured on that tablet with real files; numbers are in REPORT.md.

How to use

• Home (library): recent books with "Page N of M (x%)", then the contents of the Books and Documents folders (3 levels deep), and a File explorer button at the bottom. Long-press a recent book to remove it from the list.
• File explorer: folders and supported files; known unsupported types (DjVu, CHM, Word, KFX) are listed in grey and explain why when tapped.
• Reading: one page per screen. Tap the centre for the menu (Library, Mark, Bookmarks, direction, page slider). Tap the left/right quarter to turn. Drag to turn (the page follows your finger). Pinch to zoom 1x–5x, double-tap to zoom 2.5x and back, drag to pan (fling continues), push past the page edge while zoomed to turn. Volume keys and D-pad also turn pages. Back closes the menu first.
• Direction button (image books only): Manga ← = right-to-left (next page on the left, default for mangas), Normal/Comics → = left-to-right. PDFs, text books and TXT always read left-to-right and hide the button.
• Saved position: saved on every page change and when the screen turns off or the app closes; reopening the same file (same path and size) resumes on that page. Bookmarks: "Mark" toggles the current page, "Bookmarks" lists and jumps; stored per book.
• Previews: low-resolution page previews are built in the background while you are idle (about 10 pages/s) so scrubbing and jumping show a page instantly ("previews N%" in the menu).

Supported formats (verified on the tablet)

Format	Supported	Route (engine)	Measured	Limits
EPUB with image pages (manga/comics)	yes	image engine: native PNG/JPEG decoder, one GPU texture per page	1.86 GB / 2,787 pages: first page 2.9 s, peak 129 MB	file under 2 GB; reading order from the OPF spine
CBZ / zip of images	yes	image engine	small sample verified	under 2 GB, natural file-name order
MOBI6 comic (.mobi, image pages)	yes	image engine, records read in place, page order from the book text	1.03 GB / 2,787 pages: 2.4 s, 126 MB	page order verified against the EPUB for the one real file
KF8/AZW3 comic	yes	libmobi converts to a cached EPUB, then image engine	175–189 pages: 1.7–2.5 s, about 100 MB; order verified on all 15 volumes	file up to 150 MB (tested to 32 MB)
EPUB with text	yes	MuPDF renders reflowed pages	513 pages: 3.3 s, 174 MB; 50 MB text: 91 s, 162 MB	one chapter file at most 10 MB; opening takes about 1.5 s per MB of text
MOBI6 / AZW3 / KF8 text (no DRM)	yes	libmobi to cached EPUB, then MuPDF	Dante 2.8–3.9 s, 140–150 MB; 50 MB AZW3: 122 s, 222 MB	file up to 150 MB; MOBI6 text block at most 10 MB
PDF (text and image)	yes	MuPDF, pages rendered at 2.8 Mpixel	179 MB / 4,351 pages: first page 6.4 s, peak 192 MB	under 2 GB (larger files are refused); complex pages can take 3–5 s; password PDFs refused
TXT	yes	MuPDF	9.5 MB: 18 s, 269 MB	up to 10 MB
DOCX (Word, .docx)	yes	MuPDF converts the text to reflowed pages (layout not preserved)	2.4 MB file / 9.1 MB of text, 2,891 pages: first page 11.7 s, peak 223 MB; 0.35 MB file: 2.5 s, 140 MB	file up to 15 MB and document text up to 12 MB (the 12 MB guard is tested only up to 9.1 MB); not tested with images/tables in large files
DRM-protected AZW/AZW3/MOBI	no (message)	—	detection tested with a flagged real AZW3	cannot be opened without the owner's key

Converting what is not supported (on a computer, with Calibre)

• MOBI/AZW3 over 150 MB, or a MOBI6 text book that is one huge block: ebook-convert book.mobi book.epub
• DjVu: ebook-convert book.djvu book.cbz or ddjvu -format=pdf book.djvu book.pdf
• CHM: ebook-convert book.chm book.epub · old Word/ODT/RTF: save as DOCX or export to PDF
• KFX / DRM books: remove DRM only where the law allows it for your own books, then convert to EPUB.
• TXT over 10 MB: split it, or ebook-convert big.txt big.epub --chapter-mark pagebreak

Storage used

/data/data/com.litereader/: page index per book (small), preview images (about 150–250 MB for a 2,800-page book, deleted with the app), converted EPUBs for MOBI/AZW3 (size of the book), reading positions and bookmarks. Nothing is written to your book folders.

Engines and licences

• Image engine: own C decoder (zlib + IJG libjpeg), OpenGL ES 2.0 renderer, 2 decode threads, prefetch 3 pages ahead and 1 behind.
• Text/PDF engine (liblrmu.so, loaded only when needed): MuPDF 1.28.5 — AGPL-3.0; libmobi — LGPL-3.0; miniz (MIT/public domain). Because MuPDF is AGPL, the whole app must be offered under AGPL-3.0 with source if you ever give the APK to anyone; for private use there is no obligation. Source and build scripts are in litereader/ and scripts/.

Known limits

• Text books are laid out at a fixed size (page 360x576 pt, 11 pt font); font size and margins are not adjustable yet.
• Zoom on PDFs/text scales the rendered page (sharp to about 2x); there is no re-render at higher zoom.
• Touch gestures were verified through a gesture simulator on the real GPU engine and by code review; multi-touch translation has not been tested with real fingers by me.
• Android 4.0 only gives about 768 MB of RAM to the system; the limits above exist so that the system never kills the app.