Image decoding

Decode PNG/JPEG bytes into a dithered 1-bpp raster (no capability). More...

Functions
int	host_image_info (const uint8_t *data, size_t len, uint16_t *out_w, uint16_t *out_h)
	Decode only the image header to get its dimensions.
int	host_image_render (const uint8_t *data, size_t len, uint16_t target_w, uint8_t *out, size_t out_size, uint16_t *out_stride_bytes, uint16_t *out_height_px)
	Decode, scale to target_w (aspect preserved) and dither to 1-bpp.

Detailed Description

Decode PNG/JPEG bytes into a dithered 1-bpp raster (no capability).

Pure compute on caller memory. Output layout matches the QR and surface APIs: packed rows, MSB-first, a set bit is black. Decoding uses the same engine as the firmware image viewer (max ~1 megapixel input).

Function Documentation

host_image_info()

int host_image_info	(	const uint8_t *	data,
		size_t	len,
		uint16_t *	out_w,
		uint16_t *	out_h )

Decode only the image header to get its dimensions.

Parameters

data	Encoded PNG or JPEG bytes.
len	Byte length.
out_w	Receives the native width in pixels.
out_h	Receives the native height in pixels.

Returns

HOST_OK, HOST_ERR_INVALID_ARG, HOST_ERR_GENERIC (unsupported or corrupt image, too many pixels).

Definition at line 42 of file host_api_image.cpp.

References HOST_ERR_GENERIC, HOST_ERR_INVALID_ARG, HOST_OK, LOG_W, and TAG.

Referenced by cdc::plugin_manager::w_host_image_info().

host_image_render()

int host_image_render	(	const uint8_t *	data,
		size_t	len,
		uint16_t	target_w,
		uint8_t *	out,
		size_t	out_size,
		uint16_t *	out_stride_bytes,
		uint16_t *	out_height_px )

Decode, scale to target_w (aspect preserved) and dither to 1-bpp.

Parameters

data	Encoded PNG or JPEG bytes.
len	Byte length.
target_w	Output width in pixels, 1..1024 (e.g. 384 for thermal print).
out	Caller buffer for packed rows.
out_size	Capacity of out in bytes.
out_stride_bytes	Receives the row stride (target_w + 7) / 8.
out_height_px	Receives the scaled height.

Returns

HOST_OK, HOST_ERR_INVALID_ARG, HOST_ERR_NO_MEMORY (out too small or allocation failed), HOST_ERR_GENERIC (decode failure).

Definition at line 56 of file host_api_image.cpp.

References HOST_ERR_GENERIC, HOST_ERR_INVALID_ARG, HOST_ERR_NO_MEMORY, HOST_OK, LOG_W, cdc::core::psramAlloc(), and TAG.

Referenced by host_sprite_create_from_image(), and cdc::plugin_manager::w_host_image_render().