Pixel Sort (Glitch Art)

Math essence

For each row y, mask = metric(img[y]) >= threshold (or <= for dark mode). Walk the row; when a run of length in [min_run, max_run] is found, np.argsort the run by the selected channel and write back. A fraction `pass_prob` of rows are skipped entirely to break up the pattern. Metric is BT.601 luminance (default), or any of {R, G, B}, or hue computed from RGB max-min.

Parameters

Reference

First 60 lines of reference.py. Full source: library_external/toxi_openframeworks/PixelSort/reference.py

from __future__ import annotations

from typing import ClassVar

import numpy as np


def _build_source(dim: int, rng: np.random.Generator, frame: int) -> np.ndarray:
    yy, xx = np.mgrid[0:dim, 0:dim].astype(np.float32)
    t = frame * 0.02
    base_r = 0.5 + 0.5 * np.sin(xx / dim * 6.0 + t * 1.3)
    base_g = 0.5 + 0.5 * np.cos(yy / dim * 5.0 - t * 0.7 + 1.1)
    base_b = 0.5 + 0.5 * np.sin((xx + yy) / dim * 4.0 + t * 0.5 + 2.2)
    bands = 0.7 + 0.3 * np.sin(yy / dim * 18.0 + t * 0.4)
    perturb = rng.normal(0, 0.05, size=(dim, dim)).astype(np.float32)
    img = np.stack(
        [
            np.clip(base_r * bands + perturb * 0.5, 0, 1),
            np.clip(base_g * bands + perturb * 0.5, 0, 1),
            np.clip(base_b * bands + perturb * 0.5, 0, 1),
        ],
        axis=-1,
    )
    return (img * 255).astype(np.uint8)


class PixelSort:
    """Per-row pixel sorting (Kim Asendorf / Karsten Schmidt glitch art).

    A source image (here a procedurally-generated gradient + sinusoidal
    bands + noise wash) is processed row by row. In every row we scan
    for connected runs of pixels whose ``metric`` value lies above
    ``threshold`` (the *bright* mode); each run is sorted by the
    selected channel. The result is the streak-y, databend look that
    Kim Asendorf popularised in `ASDFPixelSort` (2010) and that
    Karsten Schmidt has used in his own glitch-art Processing sketches.

    Each ``step()`` regenerates the source with a new perturbation
    seed, producing an evolving glitch artwork rather than a single
    frame.
    """

    family: ClassVar[str] = "toxi_openframeworks"
    sketch: ClassVar[str] = "pixelsort"

    def __init__(
        self,
        dim: int = 256,
        mode: str = "bright",
        sort_channel: str = "value",
        threshold: float = 0.55,
        min_run: int = 6,
        max_run: int = 96,
        pass_prob: float = 0.7,
        frame: int = 0,
        seed: int | None = None,
    ) -> None:
        self.dim = dim
        self.mode = mode
        self.sort_channel = sort_channel