Bind a .rabook image-pool figure as a zoom source (#478). More...

#include <stdint.h>
#include "book.h"
#include "book_paged.h"
#include "ra8_err.h"
#include "zoom.h"

Include dependency graph for zoom_book.h:

Data Structures
struct	zoom_book_src_t
	One .rabook raster figure, ready to be magnified. More...

Functions
ra8_err_t	zoom_book_src_init (zoom_book_src_t bs, const book_src_t src, uint32_t img_idx)
	Look up one image in a book source and prepare it for magnification.
ra8_err_t	zoom_book_src_bind (zoom_book_src_t bs, zoom_source_t out)
	Present a bound figure to the zoom engine as a zoom_source_t.
ra8_err_t	zoom_book_read (void ctx, uint32_t x, uint32_t y, uint32_t w, uint32_t h, uint8_t out, uint32_t out_stride)
	zoom_read_fn over a .rabook image pool.

Detailed Description

Bind a .rabook image-pool figure as a zoom source (#478).

The EPUB half of the tap-to-zoom viewer. A reflow page lays a figure out at whatever size the column allows; tapping it should open the retained image, not the laid-out thumbnail, and let the reader magnify into it – which is the whole reason .rabook import stopped downscaling (#210-213, #476).

This adapter is deliberately thin, because the work is already done: book_src_image_rect owns the image-pool addressing contract, serves both retained depths (4 bpp packed and 8 bpp continuous tone) as gray8, and faults a paged book frame-by-frame so a figure larger than RAM still reads. All this file does is present that call as a zoom_read_fn and remember the two things the engine needs – the descriptor and its extent.

The TU compiles to nothing when book_paged.h is not on the include path, so an app that only magnifies tiled comics does not drag book in.

Note: Not thread-safe; inherits the (non-)reentrancy of the bound book source.

See also: zoom.h The viewport engine this feeds.; zoom_tiles.h The tiled-atlas source, for comics and manga.

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file zoom_book.h.

Function Documentation

◆ zoom_book_read()

ra8_err_t zoom_book_read	(	void *	ctx,
		uint32_t	x,
		uint32_t	y,
		uint32_t	w,
		uint32_t	h,
		uint8_t *	out,
		uint32_t	out_stride )

nodiscard

zoom_read_fn over a .rabook image pool.

Bound by zoom_book_src_bind; not normally called directly. It forwards to book_src_image_rect, which is where the gray4 nibble parity, the gray8 passthrough and the bounded paged reads all live.

Parameters

[in]	ctx	The zoom_book_src_t binding.
[in]	x	Rectangle left edge, source pixels.
[in]	y	Rectangle top edge, source pixels.
[in]	w	Rectangle width, source pixels (> 0).
[in]	h	Rectangle height, source pixels (> 0).
[out]	out	gray8 destination of at least out_stride * h bytes.
[in]	out_stride	Bytes between successive output rows (>= w).

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	The rectangle was written as gray8.
k_ra8_err_null_ptr	`ctx` or `out` is NULL.
k_ra8_err_*	Propagated verbatim from book_src_image_rect.

Precondition: ctx is a bound zoom_book_src_t.; The rectangle lies inside the bound image.

Postcondition: On k_ra8_ok every output pixel is the gray8 value of its source pixel.; On failure out content is unspecified.

Note: Not thread-safe.

See also: book_src_image_rect

Since: 0.1.0

◆ zoom_book_src_bind()

ra8_err_t zoom_book_src_bind	(	zoom_book_src_t *	bs,
		zoom_source_t *	out )

nodiscard

Present a bound figure to the zoom engine as a zoom_source_t.

Parameters

[in]	bs	Binding populated by zoom_book_src_init.
[out]	out	Source descriptor to fill.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	`out` is ready to hand to zoom_view_open.
k_ra8_err_null_ptr	`bs`, `out`, or bs->src is NULL.
k_ra8_err_invalid_arg	The bound extent is unusable (zero or too large).

Precondition: bs was populated by zoom_book_src_init.; bs outlives every view bound to out.

Postcondition: On k_ra8_ok out->ctx == bs and the extent equals the image's.; bs is not modified.

Note: Not thread-safe.

See also: zoom_view_open

Since: 0.1.0

◆ zoom_book_src_init()

ra8_err_t zoom_book_src_init	(	zoom_book_src_t *	bs,
		const book_src_t *	src,
		uint32_t	img_idx )

nodiscard

Look up one image in a book source and prepare it for magnification.

Reads the descriptor once, and fails closed on anything the viewer cannot magnify: a vector (SVG) entry, or a zero extent. A raster is accepted at either retained depth – book_src_image_rect normalises both to gray8, which is the only depth the engine reads.

Parameters

[out]	bs	Binding to populate.
[in]	src	Book source, already bound resident or paged.
[in]	img_idx	Image index, < src->hdr.image_count.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	`bs` describes a magnifiable raster.
k_ra8_err_null_ptr	`bs` or `src` is NULL.
k_ra8_err_not_supported	The entry is SVG, not a raster.
k_ra8_err_invalid_arg	The entry has a zero width or height.
k_ra8_err_*	Propagated from book_src_image.

Precondition: src was populated by book_src_resident() / book_src_paged().; bs addresses writable storage for one zoom_book_src_t.

Postcondition: On k_ra8_ok bs->src == src and bs->img is the descriptor copy.; On any error bs is not left partially bound.

Note: Not thread-safe.

See also: zoom_book_src_bind

Since: 0.1.0

Data Structures

Functions

Detailed Description

Function Documentation

◆ zoom_book_read()

◆ zoom_book_src_bind()

◆ zoom_book_src_init()