feat(visible): Doubao text-mark removal + universal region eraser

Add deterministic, CPU-only removal of the visible Doubao "豆包AI生成" mark and
a position-agnostic region eraser for any other visible watermark/logo.

- doubao_engine.py: locate (geometry, scales with width) + polarity-aware
  white-top-hat glyph mask + cv2 inpaint; coverage-gated detection and a
  dense-text safety guard. No GPU, ~30ms.
- region_eraser.py + `erase` command: inpaint arbitrary --region box(es).
  Default cv2 backend (no deps); optional big-LaMa via onnxruntime (`lama`
  extra, Carve/LaMa-ONNX, model downloaded on first use, never bundled).
- cli `visible --mark auto|gemini|doubao`: auto routes by detector confidence.
- tests for both engines; seed previously-unseeded CLI image fixtures to stop
  the Doubao detector flaking on random corners.
- .gitignore: doubao_capture/{seeds,captures} scratch (alpha-map calibration).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_cli.py

@@ -27,7 +27,9 @@ def runner():
 @pytest.fixture
 def sample_png(tmp_path: Path) -> Path:
     """Create a sample PNG for CLI testing."""
-    img = np.random.randint(0, 255, (200, 200, 3), dtype=np.uint8)
+    # Seeded: an unseeded random corner can occasionally trip the Doubao
+    # visible-mark detector, making `visible --mark auto` flaky.
+    img = np.random.default_rng(0).integers(0, 255, (200, 200, 3), dtype=np.uint8)
     path = tmp_path / "input.png"
     cv2.imwrite(str(path), img)
     return path
@@ -37,8 +39,9 @@ def _make_batch_dir(tmp_path: Path, count: int = 3) -> Path:
     """Create a directory with test images for batch testing."""
     input_dir = tmp_path / "input"
     input_dir.mkdir()
+    rng = np.random.default_rng(0)
     for i in range(count):
-        img = np.random.randint(0, 255, (100, 100, 3), dtype=np.uint8)
+        img = rng.integers(0, 255, (100, 100, 3), dtype=np.uint8)
         cv2.imwrite(str(input_dir / f"img_{i}.png"), img)
     return input_dir
 
@@ -119,7 +122,8 @@ class TestVisibleCommand:
     def test_visible_help(self, runner):
         result = runner.invoke(main, ["visible", "--help"])
         assert result.exit_code == 0
-        assert "Gemini watermark" in result.output
+        assert "visible AI watermark" in result.output
+        assert "--mark" in result.output
 
     def test_visible_basic(self, runner, sample_png, tmp_path):
         output = tmp_path / "clean.png"

tests/test_doubao_engine.py

@@ -0,0 +1,98 @@
+"""Tests for the Doubao visible-watermark engine."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import cv2
+import numpy as np
+import pytest
+
+from remove_ai_watermarks.doubao_engine import DoubaoEngine, load_image_bgr
+
+SAMPLE = Path(__file__).resolve().parents[1] / "data" / "samples" / "doubao-1.png"
+
+
+# ── Locate ──────────────────────────────────────────────────────────
+
+
+class TestLocate:
+    def test_box_anchored_bottom_right(self):
+        eng = DoubaoEngine()
+        img = np.zeros((2048, 2048, 3), np.uint8)
+        loc = eng.locate(img)
+        # right and bottom edges sit close to the image corner (within margins)
+        assert 2048 - (loc.x + loc.w) < int(2048 * 0.03)
+        assert 2048 - (loc.y + loc.h) < int(2048 * 0.03)
+        assert loc.is_fallback  # geometry anchor, no bundled template yet
+
+    def test_box_scales_with_width(self):
+        eng = DoubaoEngine()
+        small = eng.locate(np.zeros((1024, 1024, 3), np.uint8))
+        large = eng.locate(np.zeros((2048, 2048, 3), np.uint8))
+        # width-relative geometry: 2x wider image -> ~2x wider box
+        assert large.w == pytest.approx(small.w * 2, rel=0.1)
+
+
+# ── Detect + remove on the real sample ──────────────────────────────
+
+
+@pytest.mark.skipif(not SAMPLE.exists(), reason="sample image not present")
+class TestRealSample:
+    def test_detects_watermark(self):
+        eng = DoubaoEngine()
+        det = eng.detect(load_image_bgr(SAMPLE))
+        assert det.detected
+        assert det.confidence > 0.0
+        assert det.coverage > 0.04
+
+    def test_remove_reduces_glyph_coverage(self):
+        eng = DoubaoEngine()
+        img = load_image_bgr(SAMPLE)
+        before = eng.detect(img).coverage
+        out = eng.remove_watermark(img)
+        after = eng.detect(out).coverage
+        # the inpaint should clear most glyph pixels from the corner box
+        assert after < before * 0.5
+
+    def test_pixels_outside_box_untouched(self):
+        eng = DoubaoEngine()
+        img = load_image_bgr(SAMPLE)
+        out = eng.remove_watermark(img)
+        # top-left quadrant is far from the bottom-right mark: must be identical
+        h, w = img.shape[:2]
+        assert np.array_equal(img[: h // 2, : w // 2], out[: h // 2, : w // 2])
+
+
+# ── Negative + safety guard ─────────────────────────────────────────
+
+
+class TestNegativeAndGuard:
+    def test_clean_image_not_detected(self):
+        eng = DoubaoEngine()
+        # smooth gradient, no watermark
+        ramp = np.tile(np.linspace(0, 255, 1024, dtype=np.uint8), (1024, 1))
+        img = cv2.cvtColor(ramp, cv2.COLOR_GRAY2BGR)
+        det = eng.detect(img)
+        assert not det.detected
+
+    def test_clean_image_returned_unchanged(self):
+        eng = DoubaoEngine()
+        ramp = np.tile(np.linspace(0, 255, 1024, dtype=np.uint8), (1024, 1))
+        img = cv2.cvtColor(ramp, cv2.COLOR_GRAY2BGR)
+        out = eng.remove_watermark(img)
+        assert np.array_equal(img, out)
+
+    def test_document_background_guard(self):
+        """A dense high-frequency corner (document-like) trips the coverage
+        guard, so the image is left untouched rather than smeared."""
+        eng = DoubaoEngine()
+        rng = np.random.default_rng(0)
+        img = np.full((1024, 1024, 3), 255, np.uint8)
+        # fill the bottom-right box area with random grayish text-like noise
+        loc = eng.locate(img)
+        x, y, bw, bh = loc.bbox
+        noise = rng.integers(150, 246, size=(bh, bw), dtype=np.uint8)
+        img[y : y + bh, x : x + bw] = noise[:, :, None]
+        out = eng.remove_watermark(img)
+        assert np.array_equal(img, out)

tests/test_region_eraser.py

@@ -0,0 +1,75 @@
+"""Tests for the universal region eraser."""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+from remove_ai_watermarks.region_eraser import boxes_to_mask, erase, lama_available
+
+
+class TestBoxesToMask:
+    def test_mask_set_inside_box(self):
+        mask = boxes_to_mask((100, 100), [(10, 20, 30, 40)], dilate=0)
+        assert mask[25, 15] == 255  # inside
+        assert mask[0, 0] == 0  # outside
+        assert mask.shape == (100, 100)
+
+    def test_multiple_boxes(self):
+        mask = boxes_to_mask((100, 100), [(0, 0, 10, 10), (90, 90, 10, 10)], dilate=0)
+        assert mask[5, 5] == 255
+        assert mask[95, 95] == 255
+        assert mask[50, 50] == 0
+
+    def test_dilate_grows_mask(self):
+        m0 = boxes_to_mask((100, 100), [(40, 40, 10, 10)], dilate=0)
+        m5 = boxes_to_mask((100, 100), [(40, 40, 10, 10)], dilate=5)
+        assert m5.sum() > m0.sum()
+
+    def test_box_clipped_to_bounds(self):
+        # box partly outside the image must not raise and stays in-bounds
+        mask = boxes_to_mask((50, 50), [(40, 40, 100, 100)], dilate=0)
+        assert mask[45, 45] == 255
+
+
+class TestEraseCv2:
+    def _image_with_logo(self) -> tuple[np.ndarray, tuple[int, int, int, int]]:
+        img = np.full((200, 200, 3), 120, np.uint8)  # flat gray background
+        box = (140, 160, 50, 30)
+        x, y, w, h = box
+        img[y : y + h, x : x + w] = (255, 255, 255)  # bright "logo"
+        return img, box
+
+    def test_erase_changes_region(self):
+        img, box = self._image_with_logo()
+        out = erase(img, boxes=[box], backend="cv2")
+        x, y, w, h = box
+        # on a flat background the logo region should be repainted near gray
+        region = out[y : y + h, x : x + w]
+        assert abs(float(region.mean()) - 120) < 20
+        assert not np.array_equal(out, img)
+
+    def test_pixels_outside_box_untouched(self):
+        img, box = self._image_with_logo()
+        out = erase(img, boxes=[box], backend="cv2", dilate=0)
+        # a far corner must be identical
+        assert np.array_equal(img[:50, :50], out[:50, :50])
+
+    def test_no_boxes_returns_copy(self):
+        img = np.full((100, 100, 3), 50, np.uint8)
+        out = erase(img, boxes=[], backend="cv2")
+        assert np.array_equal(img, out)
+
+    def test_empty_mask_returns_copy(self):
+        img = np.full((100, 100, 3), 50, np.uint8)
+        out = erase(img, mask=np.zeros((100, 100), np.uint8), backend="cv2")
+        assert np.array_equal(img, out)
+
+
+class TestLamaBackend:
+    def test_lama_raises_when_unavailable(self):
+        img = np.full((100, 100, 3), 50, np.uint8)
+        if lama_available():
+            pytest.skip("onnxruntime installed; cannot test the unavailable path")
+        with pytest.raises(RuntimeError, match="onnxruntime"):
+            erase(img, boxes=[(10, 10, 20, 20)], backend="lama")