wai-rs: jpegai_pipeline::lef_filter — LEF adaptive-sharpness post-filter #10
2026-07-14
wai-rs: jpegai_pipeline::lef_filter — LEF adaptive-sharpness post-filter (float-exact)
Second pixel-domain post-filter — a scale-gated unsharp mask on the luma plane: n = y_in / 255 blur = clamp( conv3x3(n, [[5,5,5],[5,24,5],[5,5,5]]/64), 0, 1 ) // valid; border keeps n factor = mag[k] where region in [thr[k], thr[k+1]) (k=0,1) or region >= thr[2]; else 1 out = clamp( blur + (n - blur)*factor, 0, 1 ) * 255 The 3x3 conv is "valid" (no padding) — interior pixels blur, the 1-pixel border passes through — matching the reference's pad-and-mask trick. `region` gates the sharpening strength: the scale grid (sigma, 16x16) nearest-upsampled to pixel resolution. Validated against the reference fixture (input luma + 16x16 scale + thr/mag → sharpened luma): max|Δ| = 1.5e-5 (f32-vs-f64), SNR 153 dB. Plus unit tests for the flat-plane invariance, the border pass-through, and the factor>1 sharpening gate. Co-Authored-By: Claude Opus 4.8 <[email protected]>