rxing

Many 2D readers in rxing implement the ImmutableReader trait. This allows you to call immutable_decode or immutable_decode_with_hints without requiring the reader instance to be declared as mutable (mut).

This is particularly useful for using individual symbol readers in a Lazy static context without requiring unsafe code.

Note: Not all readers support this. The following readers do not implement ImmutableReader because they require internal state:

• MultiFormatReader
• MultiUseMultiFormatReader
• FilteredImageReader
• MultiFormatOneDReader

static LAZY_STATIC_QR_READER: Lazy<QRCodeReader> = Lazy::new(QRCodeReader::default);

fn main() {
    let result = LAZY_STATIC_QR_READER.immutable_decode(
        &mut BinaryBitmap::new(
            HybridBinarizer::new(
                Luma8LuminanceSource::new(luma_data, width, height),
            )
        )
    );
}

You can customize the library's capabilities using Cargo feature flags. The default feature set includes image, client_support, image_formats, serde, encoding_rs, encoders, decoders, full_barcode_format_support, and multi_barcode_readers.

Core & Engine

• image (default): Required for image manipulation and reading.
• image_formats (default): Enables support for all image crate formats.
• encoders (default): Enables barcode encoding.
• decoders (default): Enables barcode decoding.
• multi_barcode_readers (default): Enables reading multiple barcodes in one image.
• client_support (default): Enables parsing barcode result types (e.g., URLs, contacts, WiFi).
• serde (default): Adds serde::Serialize and serde::Deserialize support to public structs.
• encoding_rs (default): Uses encoding_rs for high-performance character encoding.

Symbology Granular Support

• full_barcode_format_support (default): Enables all modules listed below.
• aztec: Aztec barcodes.
• datamatrix: Data Matrix barcodes.
• maxicode: MaxiCode barcodes.
• oned: 1D barcodes.
• pdf417: PDF417 barcodes.
• qrcode: QR Code barcodes.

Advanced & Optional

• allow_forced_iso_ied_18004_compliance: Force ISO/IED 18004 compliance (use with caution).
• legacy_encoding: Uses the legacy encoding crate for exact compatibility with older versions.
• no_character_set_support: Disables all CharacterSet support.
• otsu_level: Adds OtsuLevelBinarizer (untested).
• reverse_pyramid_layers: Reverses pyramid scan order for FilteredImageReader.
• svg_read: Enable SVG file reading.
• svg_write: Enable SVG file writing.
• wasm_support: Enables WASM compatibility.
• experimental_features: Enables risky experimental features.

The BinaryBitmap<B> struct is the core representation of 1-bit data used by ZXing readers to decode barcodes. It wraps a Binarizer and provides access to the binarized image data as either rows, lines, or a full 2D matrix.

Key characteristics:

• Lazy Evaluation: The 2D matrix is computed lazily and cached to avoid expensive re-computation.
• Copy-on-Write: Using get_black_matrix_mut() creates a local copy of the binarizer's cache if you need to perform mutations (like inversion), ensuring the original binarizer's cache remains uncorrupted.
• Inversion Support: You can toggle between normal and inverted views using invert(), which is useful for decoders that need to attempt reading both black-on-white and white-on-black images.

// Example initialization (requires a Binarizer implementation)
let binarizer = MyBinarizer::new(my_luminance_source);
let bitmap = BinaryBitmap::new(binarizer);

// Accessing the 2D matrix
let matrix = bitmap.get_black_matrix();

// Inverting the view
let mut mutable_bitmap = bitmap;
mutable_bitmap.invert();

GenericGFPoly represents an immutable polynomial whose coefficients are elements of a Galois Field (GenericGF). It is used for performing polynomial arithmetic required by Reed-Solomon error correction.

Key behaviors:

• Coefficient Order: Coefficients are provided from most significant (highest-power term) to least significant.
• Immutability: Instances are immutable; arithmetic operations return new GenericGFPoly instances.
• Field Consistency: Arithmetic operations like addOrSubtract, multiply, and divide require that both polynomials belong to the same GenericGF field. Attempting to operate on polynomials from different fields will return an error.
• Zero Polynomial: A polynomial where all coefficients are zero is treated as the monomial "0".

// Example of creating a polynomial from coefficients
// Note: coefficients are most-significant first
let poly = GenericGFPoly::new(field_ref, &[1, 0, 3])?; // Represents 1x^2 + 0x + 3