Add background stripping and cleaned badge fixture

tests/fixtures/real/ai-badge-cleaned.json

@@ -0,0 +1,14 @@
+{
+  "id": "ai-badge-cleaned",
+  "kind": "real-ai-generated-emblem",
+  "description": "Manually cleaned transparent version of the AI badge emblem used as a real-image regression fixture.",
+  "source_image": "C:\\Users\\Meta\\.codex\\generated_images\\019db22f-5487-7a31-8a67-45f0c801dd7c\\ig_0b9862296469b4740169e7fbc657ac81919d4d2267673f6bae.png",
+  "revision": 3,
+  "notes": [
+    "Use this version when evaluating lattice inference and thin-feature preservation without the baked checkerboard background contaminating results.",
+    "Primary failure region is the sword tip and nearby outline taper, plus other sharp single-pixel and near-single-pixel features at mixed orientations.",
+    "Keep the raw checkerboard-background version around separately when testing the automatic background stripper.",
+    "Revision 2 reapplies transparency as a raster mask and thresholds that mask to suppress subtle dark-background glow left by the earlier cleanup.",
+    "Revision 3 binarizes the repo fixture copy to strict 0/255 alpha so the regression asset stays unambiguous."
+  ]
+}

tests/test_cli.py

@@ -16,3 +16,14 @@ def test_default_command_runs_without_explicit_run_subcommand(tmp_path: Path) ->
     exit_code = main([str(input_path), "--out", str(output_path), "--steps", "8"])
     assert exit_code == 0
     assert output_path.exists()
+
+
+def test_default_command_accepts_strip_background_flag(tmp_path: Path) -> None:
+    source = make_emblem(16, 16)
+    fake = fake_pixelize(source, upscale=8, phase_x=0.2, phase_y=0.25, blur_radius=0.4)
+    input_path = tmp_path / "input.png"
+    output_path = tmp_path / "output.png"
+    save_rgba(input_path, fake)
+    exit_code = main([str(input_path), "--out", str(output_path), "--steps", "0", "--strip-background"])
+    assert exit_code == 0
+    assert output_path.exists()

tests/test_metrics.py

@@ -5,6 +5,8 @@ import numpy as np
 from repixelizer.metrics import (
     exact_match_ratio,
     foreground_adjacency_error,
+    foreground_edge_concentration,
+    foreground_edge_position_error,
     foreground_exact_match_ratio,
     foreground_motif_error,
     foreground_reconstruction_error,
@@ -66,6 +68,35 @@ def test_texture_metrics_track_adjacency_and_local_motifs() -> None:
     assert foreground_motif_error(original, same_colors_wrong_structure) > 0.0
 
 
+def test_edge_position_metric_prefers_crisp_shift_to_blurry_smear() -> None:
+    original = np.zeros((7, 7, 4), dtype=np.float32)
+    original[1:6, 3] = np.asarray([1.0, 1.0, 1.0, 1.0], dtype=np.float32)
+
+    shifted = np.zeros_like(original)
+    shifted[1:6, 4] = np.asarray([1.0, 1.0, 1.0, 1.0], dtype=np.float32)
+
+    blurred = np.zeros_like(original)
+    blurred[1:6, 2] = np.asarray([0.4, 0.4, 0.4, 1.0], dtype=np.float32)
+    blurred[1:6, 3] = np.asarray([0.7, 0.7, 0.7, 1.0], dtype=np.float32)
+    blurred[1:6, 4] = np.asarray([0.4, 0.4, 0.4, 1.0], dtype=np.float32)
+
+    assert foreground_edge_position_error(original, original) == 0.0
+    assert foreground_edge_position_error(original, shifted) > 0.0
+    assert foreground_edge_position_error(original, blurred) > foreground_edge_position_error(original, shifted)
+
+
+def test_edge_concentration_prefers_crisp_edges_to_blurry_smear() -> None:
+    shifted = np.zeros((7, 7, 4), dtype=np.float32)
+    shifted[1:6, 4] = np.asarray([1.0, 1.0, 1.0, 1.0], dtype=np.float32)
+
+    blurred = np.zeros_like(shifted)
+    blurred[1:6, 2] = np.asarray([0.4, 0.4, 0.4, 1.0], dtype=np.float32)
+    blurred[1:6, 3] = np.asarray([0.7, 0.7, 0.7, 1.0], dtype=np.float32)
+    blurred[1:6, 4] = np.asarray([0.4, 0.4, 0.4, 1.0], dtype=np.float32)
+
+    assert foreground_edge_concentration(shifted) > foreground_edge_concentration(blurred)
+
+
 def test_source_lattice_consistency_prefers_matching_cell_structure() -> None:
     lowres = np.asarray(
         [

tests/test_pipeline.py

@@ -74,6 +74,30 @@ def test_pipeline_preserves_transparency_for_sprite(tmp_path: Path) -> None:
     assert partial.size == 0
 
 
+def test_pipeline_can_strip_checkerboard_background(tmp_path: Path) -> None:
+    source = make_sprite(24, 24)
+    checker = np.ones_like(source)
+    checker[..., 3] = 1.0
+    for y in range(checker.shape[0]):
+        for x in range(checker.shape[1]):
+            tile = 0.97 if ((x // 4) + (y // 4)) % 2 == 0 else 0.91
+            checker[y, x, :3] = tile
+    alpha = source[..., 3:4]
+    opaque_input = checker.copy()
+    opaque_input[..., :3] = source[..., :3] * alpha + checker[..., :3] * (1.0 - alpha)
+
+    input_path = tmp_path / "input.png"
+    output_path = tmp_path / "output.png"
+
+    from repixelizer.io import save_rgba
+
+    save_rgba(input_path, opaque_input)
+    result = run_pipeline(input_path, output_path, target_size=24, steps=0, strip_background=True)
+    assert result.source_rgba[..., 3].min() < 0.05
+    assert result.output_rgba[..., 3].min() < 0.05
+    assert result.output_rgba[..., 3].max() > 0.9
+
+
 def test_pipeline_can_emit_initialized_output_without_optimizer_steps(tmp_path: Path) -> None:
     source = make_emblem(24, 24)
     fake = fake_pixelize(source, upscale=10, phase_x=0.15, phase_y=0.2, blur_radius=0.6, warp_strength=0.2, warp_detail=5)

tests/test_preprocess.py

@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+import numpy as np
+
+from repixelizer.preprocess import strip_edge_background
+
+
+def test_strip_edge_background_removes_light_checkerboard_and_preserves_subject() -> None:
+    rgba = np.ones((80, 80, 4), dtype=np.float32)
+    rgba[..., 3] = 1.0
+    for y in range(80):
+        for x in range(80):
+            tile = 0.97 if ((x // 4) + (y // 4)) % 2 == 0 else 0.91
+            rgba[y, x, :3] = tile
+    rgba[12:68, 10:70] = np.array([0.1, 0.7, 0.2, 1.0], dtype=np.float32)
+    for y in range(24, 56):
+        for x in range(26, 54):
+            tile = 0.97 if ((x // 4) + (y // 4)) % 2 == 0 else 0.91
+            rgba[y, x, :3] = tile
+    rgba[20:60, 16:20] = np.array([0.98, 0.97, 0.96, 1.0], dtype=np.float32)
+
+    stripped = strip_edge_background(rgba)
+
+    assert stripped[0, 0, 3] == 0.0
+    assert stripped[4, 4, 3] == 0.0
+    assert stripped[40, 40, 3] == 0.0
+    assert stripped[30, 18, 3] == 1.0
+    assert np.allclose(stripped[30, 18, :3], rgba[30, 18, :3])
+    assert stripped[16, 16, 3] == 1.0
+
+
+def test_strip_edge_background_handles_trivial_monochrome_background() -> None:
+    rgba = np.zeros((32, 32, 4), dtype=np.float32)
+    rgba[..., :3] = np.array([0.2, 0.3, 0.8], dtype=np.float32)
+    rgba[..., 3] = 1.0
+    rgba[8:24, 8:24] = np.array([1.0, 0.6, 0.1, 1.0], dtype=np.float32)
+
+    stripped = strip_edge_background(rgba)
+
+    assert stripped[0, 0, 3] == 0.0
+    assert stripped[16, 16, 3] == 1.0
+    assert np.allclose(stripped[16, 16, :3], rgba[16, 16, :3])