Add jpegtran lossless rotation and EXIF orientation handling
DCT steganography improvements: - Add _apply_exif_orientation() to fix portrait photos encoding rotated - Add _jpegtran_rotate() for lossless JPEG rotation preserving DCT data - Add rotation fallback in extract_from_dct() - tries 0°, 90°, 180°, 270° - Quick header validation to skip invalid rotations efficiently - Fix: wrap debug.print in try/except to prevent extraction failures Web UI rotate tool: - Use jpegtran for JPEGs (lossless, preserves DCT steganography) - Fall back to PIL for non-JPEGs - Dynamic UI shows "DCT Safe" for JPEGs, warning for other formats This enables the workflow: encode → compress → rotate → decode Rotated stego JPEGs can now be decoded by trying all orientations. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Aaron D. Lee
@@ -2100,8 +2100,11 @@ def api_tools_exif_clear():
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@app.route("/api/tools/rotate", methods=["POST"])
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@login_required
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def api_tools_rotate():
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"""Rotate and/or flip an image."""
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"""Rotate and/or flip an image, using lossless jpegtran for JPEGs."""
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from PIL import Image
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import shutil
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import subprocess
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import tempfile
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image_file = request.files.get("image")
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if not image_file:
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@@ -2112,22 +2115,115 @@ def api_tools_rotate():
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flip_v = request.form.get("flip_v", "false").lower() == "true"
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try:
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img = Image.open(io.BytesIO(image_file.read()))
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image_data = image_file.read()
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img = Image.open(io.BytesIO(image_data))
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original_format = img.format # JPEG, PNG, etc.
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img.close()
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# Apply rotation (PIL rotates counter-clockwise, so negate)
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if rotation:
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img = img.rotate(-rotation, expand=True)
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# For JPEGs, use jpegtran for lossless rotation/flip (preserves DCT stego)
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has_jpegtran = shutil.which("jpegtran") is not None
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use_jpegtran = original_format == "JPEG" and has_jpegtran and (rotation or flip_h or flip_v)
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# Apply flips
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if flip_h:
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img = img.transpose(Image.FLIP_LEFT_RIGHT)
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if flip_v:
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img = img.transpose(Image.FLIP_TOP_BOTTOM)
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if use_jpegtran:
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# Chain jpegtran operations for lossless transformation
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current_data = image_data
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# Output as PNG (lossless)
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buffer = io.BytesIO()
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img.save(buffer, format="PNG")
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buffer.seek(0)
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# Apply rotation first
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if rotation in (90, 180, 270):
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with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as f:
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f.write(current_data)
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input_path = f.name
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output_path = tempfile.mktemp(suffix=".jpg")
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try:
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result = subprocess.run(
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["jpegtran", "-rotate", str(rotation), "-copy", "all", "-trim",
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"-outfile", output_path, input_path],
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capture_output=True, timeout=30
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)
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if result.returncode == 0:
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with open(output_path, "rb") as f:
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current_data = f.read()
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finally:
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for p in [input_path, output_path]:
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try:
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os.unlink(p)
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except OSError:
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pass
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# Apply horizontal flip
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if flip_h:
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with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as f:
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f.write(current_data)
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input_path = f.name
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output_path = tempfile.mktemp(suffix=".jpg")
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try:
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result = subprocess.run(
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["jpegtran", "-flip", "horizontal", "-copy", "all", "-trim",
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"-outfile", output_path, input_path],
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capture_output=True, timeout=30
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)
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if result.returncode == 0:
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with open(output_path, "rb") as f:
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current_data = f.read()
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finally:
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for p in [input_path, output_path]:
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try:
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os.unlink(p)
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except OSError:
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pass
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# Apply vertical flip
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if flip_v:
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with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as f:
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f.write(current_data)
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input_path = f.name
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output_path = tempfile.mktemp(suffix=".jpg")
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try:
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result = subprocess.run(
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["jpegtran", "-flip", "vertical", "-copy", "all", "-trim",
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"-outfile", output_path, input_path],
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capture_output=True, timeout=30
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)
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if result.returncode == 0:
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with open(output_path, "rb") as f:
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current_data = f.read()
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finally:
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for p in [input_path, output_path]:
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try:
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os.unlink(p)
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except OSError:
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pass
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buffer = io.BytesIO(current_data)
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mimetype = "image/jpeg"
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ext = "jpg"
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else:
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# Fallback to PIL for non-JPEGs or when jpegtran unavailable
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img = Image.open(io.BytesIO(image_data))
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# Apply rotation (PIL rotates counter-clockwise, so negate)
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if rotation:
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img = img.rotate(-rotation, expand=True)
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# Apply flips
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if flip_h:
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img = img.transpose(Image.FLIP_LEFT_RIGHT)
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if flip_v:
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img = img.transpose(Image.FLIP_TOP_BOTTOM)
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# Preserve original format
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buffer = io.BytesIO()
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if original_format == "JPEG":
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if img.mode in ("RGBA", "P"):
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img = img.convert("RGB")
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img.save(buffer, format="JPEG", quality=95)
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mimetype = "image/jpeg"
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ext = "jpg"
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else:
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img.save(buffer, format="PNG")
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mimetype = "image/png"
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ext = "png"
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buffer.seek(0)
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stem = (
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image_file.filename.rsplit(".", 1)[0]
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@@ -2136,9 +2232,9 @@ def api_tools_rotate():
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)
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return send_file(
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buffer,
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mimetype="image/png",
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mimetype=mimetype,
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as_attachment=True,
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download_name=f"{stem}_transformed.png",
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download_name=f"{stem}_transformed.{ext}",
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)
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except Exception as e:
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return jsonify({"success": False, "error": str(e)}), 500
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