* qrcode: add QR decoder
Decodes a QR code from a grayscale image or a module matrix: adaptive
binarization, finder pattern search by run ratios, perspective sampling
with alignment pattern refinement, format info, unmasking, block
de-interleaving, Reed-Solomon correction, and numeric, alphanumeric,
byte (with ECI), and Kanji segments.
Fixtures are packed matrices from python-qrcode 8.2 covering every
version and level, plus Segno 1.6.6 matrices for the ECI cases.
* qrcode: tune decoder for the device
Measured on a comma mici with real cabin frames downsampled to 672x380,
the size the eSIM screen scans at. Per frame: 30 ms -> 8 ms with no
code in view, 42 ms -> 13 ms with a code.
- binarize: fixed two-radius fill from one integral image instead of an
iterative outward fill (a dark cabin is almost all flat tiles), tile
stats on a contiguous layout, flat tiles decided whole so sensor noise
cannot become speckle, uint8 threshold compare
- finder search: scan every 4th row, build column runs only at
candidate columns
- alignment search starts at a 2-module radius
- Reed-Solomon syndromes through table lookups, placement order cached
* qrcode: simplify decoder
Fold the function-module mask into _data_coords and the format
coordinates into _read_format, evaluate masks directly on the data
coordinates, compact the ECI, numeric, and alphanumeric parsing, and
flatten the retry loop in decode. No behavior change.
Replace the level-L-only Reed-Solomon parameters, the single hardcoded
format word, and the bitwise GF(256) multiply with the full EC table,
the 32 format words, and log/antilog tables. Block splitting and
interleaving move into _block_lengths and _interleaved. This is the
structure a decoder needs to read any version, level, and mask; the
encoder's module matrices are unchanged and test_encoder pins them.
The closed-form step between alignment patterns rounds the wrong way
for version 32 (28 instead of 26). Use the form that is right for every
version. The encoder only emits versions 1-20, so its output is
unchanged.
Trey Moen