feat(knowledge): 知识源维护与 TXT/Markdown/PDF 导入

支持文本、Markdown 与非扫描 PDF 上传解析，展示提取文本与切块结果。

backend/tests/services/test_image_security.py

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+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+import io
+
+import pytest
+from fastapi import HTTPException
+from PIL import Image
+
+from app.services.image_security import sanitize_image
+
+RASTER = {"image/png", "image/jpeg", "image/webp"}
+
+
+def _img_bytes(fmt: str, size=(64, 48), color=(200, 30, 30)) -> bytes:
+    buf = io.BytesIO()
+    Image.new("RGB", size, color).save(buf, format=fmt)
+    return buf.getvalue()
+
+
+def test_png_reencoded_to_png():
+    out, ctype, ext = sanitize_image(
+        _img_bytes("PNG"), allowed_content_types=RASTER, max_bytes=2_000_000, max_dim=4000
+    )
+    assert ctype == "image/png" and ext == ".png"
+    assert Image.open(io.BytesIO(out)).format == "PNG"
+
+
+def test_jpeg_stays_jpeg():
+    out, ctype, ext = sanitize_image(
+        _img_bytes("JPEG"), allowed_content_types=RASTER, max_bytes=2_000_000, max_dim=4000
+    )
+    assert ctype == "image/jpeg" and ext == ".jpg"
+    assert Image.open(io.BytesIO(out)).format == "JPEG"
+
+
+def test_fit_downscales_longest_side():
+    out, _c, _e = sanitize_image(
+        _img_bytes("PNG", size=(1200, 600)),
+        allowed_content_types=RASTER,
+        max_bytes=2_000_000,
+        max_dim=4000,
+        fit=512,
+    )
+    w, h = Image.open(io.BytesIO(out)).size
+    assert max(w, h) == 512 and (w, h) == (512, 256)
+
+
+def test_rejects_non_image():
+    with pytest.raises(HTTPException) as e:
+        sanitize_image(b"not an image", allowed_content_types=RASTER, max_bytes=2_000_000, max_dim=4000)
+    assert e.value.status_code == 400
+
+
+def test_rejects_oversized_bytes():
+    with pytest.raises(HTTPException) as e:
+        sanitize_image(_img_bytes("PNG"), allowed_content_types=RASTER, max_bytes=10, max_dim=4000)
+    assert e.value.status_code == 400
+
+
+def test_rejects_dimensions_over_cap():
+    with pytest.raises(HTTPException) as e:
+        sanitize_image(
+            _img_bytes("PNG", size=(300, 300)),
+            allowed_content_types=RASTER,
+            max_bytes=2_000_000,
+            max_dim=100,
+        )
+    assert e.value.status_code == 400
+
+
+def test_rejects_disallowed_format():
+    # GIF is a valid image but not in the allowlist here → rejected.
+    with pytest.raises(HTTPException) as e:
+        sanitize_image(_img_bytes("GIF"), allowed_content_types=RASTER, max_bytes=2_000_000, max_dim=4000)
+    assert e.value.status_code == 400
+
+
+def test_empty_rejected():
+    with pytest.raises(HTTPException):
+        sanitize_image(b"", allowed_content_types=RASTER, max_bytes=2_000_000, max_dim=4000)