Module scan 

Available on crate feature scan only.

Reading barcodes back out of images.

The mirror of render, meeting the rest of the crate at the same seam:

image ──▶ GrayImage ──▶ binarize ──▶ BitMatrix ──▶ Decoder::decode ──▶ payload

A Scanner locates the symbol and turns pixels back into modules; a Decoder turns modules back into a payload. Neither half knows what the other is doing, so adding a scannable symbology means implementing Decoder and describing the symbology’s character structure in SymbologyKind::linear_character, not touching this module.

Example

use smart_package_tracker::{Barcode, RenderOptions, scan};

let png = Barcode::code128("PKG-9ED9285C")?.to_png(&RenderOptions::default())?;

let found = scan::scan_png(&png)?;
assert_eq!(found.payload(), "PKG-9ED9285C");

What this handles, and what it does not

Reading a barcode off a photograph of a parcel and reading one out of a rendered label, a flatbed scan or a screenshot are different problems. This solves the second.

Handled: any module width; extra margin or a crop flush to the bars; the symbol anywhere in a larger image; light-on-dark as well as dark-on-light; uneven lighting across the image; moderate noise and blur; a label turned on its side, since columns are scanned as well as rows; and a printed width that drifts from nominal, because each character is measured against its own width rather than against one estimate for the whole symbol.

Not handled: rotation by anything other than a quarter turn, perspective, and the curvature of a barcode wrapped around a parcel. Those want a dedicated scanning engine, not a label-generation crate — reach for one of those if you are decoding camera frames.

Only linear symbologies can be read. There is no QR decoder here; QR encodes but does not scan.

Structs

GrayImage

An 8-bit greyscale image: what a scanner actually works on.

Scan

A barcode found in an image.

Scanner

Reads barcodes out of images.

Functions

scan_pngpng

Read any barcode this crate can decode out of a PNG image.

scan_png_filepng and std

Read any barcode this crate can decode out of a PNG file.