test: add the generator for the stripe test fixtures

tests/data/make_stripes.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python
+"""
+Generate the stripe test fixture images committed to ``tests/data/``.
+
+Run to regenerate the fixtures if they are ever lost or need to be recreated
+from scratch::
+
+    $ python tests/data/make_stripes.py
+    $ python tests/data/make_stripes.py --outdir /tmp/stripes   # elsewhere
+
+Images created:
+
+``stripes.png``
+    RGB, 1000 × 400 px, uint8.  Five vertical stripes each 200 px wide:
+    black | red | green | blue | white
+
+``stripes_a.png``
+    RGBA, 1000 × 400 px, uint8.  Same stripes as ``stripes.png`` with a fully
+    opaque alpha plane (alpha = 255 throughout).
+
+These images are used by:
+
+- ``tests/base/test_io.py``  -- ``TestBaseStripeIO`` (``iread`` / ``idisp``)
+- ``tests/test_image_io.py`` -- ``TestStripeImageIO`` (``Image.Read`` / ``Image.disp``)
+
+The images are written with OpenCV directly (not via ``iwrite``) so they are
+independent of any MVTB I/O logic.
+"""
+
+import argparse
+from pathlib import Path
+
+import cv2
+import numpy as np
+
+HEIGHT = 400
+WIDTH = 1000
+STRIPE_W = 200
+
+# Stripes in BGR order (OpenCV native write order)
+STRIPES_BGR = [
+    (0, 0, 0),  # black
+    (0, 0, 255),  # red   (B=0, G=0, R=255 in BGR)
+    (0, 255, 0),  # green
+    (255, 0, 0),  # blue  (B=255, G=0, R=0 in BGR)
+    (255, 255, 255),  # white
+]
+
+
+def make_stripes(out_dir: Path) -> None:
+    """Write ``stripes.png`` and ``stripes_a.png`` into ``out_dir``.
+
+    :param out_dir: directory to write the images to, created if necessary
+    """
+    out_dir.mkdir(parents=True, exist_ok=True)
+
+    # --- stripes.png (BGR → written as RGB by PNG codec) -------------------
+    im_bgr = np.zeros((HEIGHT, WIDTH, 3), dtype=np.uint8)
+    for i, bgr in enumerate(STRIPES_BGR):
+        im_bgr[:, i * STRIPE_W : (i + 1) * STRIPE_W] = bgr
+
+    path_rgb = out_dir / "stripes.png"
+    cv2.imwrite(str(path_rgb), im_bgr)
+    print(f"Written: {path_rgb}")
+
+    # --- stripes_a.png (BGRA) ----------------------------------------------
+    im_bgra = np.zeros((HEIGHT, WIDTH, 4), dtype=np.uint8)
+    im_bgra[:, :, :3] = im_bgr
+    im_bgra[:, :, 3] = 255  # fully opaque
+
+    path_rgba = out_dir / "stripes_a.png"
+    cv2.imwrite(str(path_rgba), im_bgra)
+    print(f"Written: {path_rgba}")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__.split("\n")[1])
+    parser.add_argument(
+        "--outdir",
+        type=Path,
+        default=Path(__file__).resolve().parent,
+        help="output directory, defaults to the directory containing this script",
+    )
+    make_stripes(parser.parse_args().outdir)