image resize ok
This commit is contained in:
Zeecka
@@ -8,191 +8,163 @@ from typing import Any, List
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from ..app import app
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from ..models import IHDR
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from .utils import PNG, update_data
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from .base_analyzer import SubprocessAnalyzer
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from .utils import PNG
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def write_recovered_png(
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png_bytes: bytearray,
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width: int,
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height: int,
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output_path: Path,
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) -> None:
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"""
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Rebuilds a PNG by patching IHDR width/height and writes it to disk.
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"""
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height_bytes = height.to_bytes(4, byteorder="big")
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width_bytes = width.to_bytes(4, byteorder="big")
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class ResizeAnalyzer(SubprocessAnalyzer):
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"""Analyzer for image resize."""
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full_png_data = (
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png_bytes[:16] # Splicing: [Start...IHDR+4] + [W] + [H] + [IHDR+12...End]
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+ width_bytes
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+ height_bytes
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+ png_bytes[24:]
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)
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png: PNG
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with output_path.open("wb") as out_f:
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out_f.write(full_png_data)
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def __init__(self, *args):
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super().__init__("image_resize", *args, has_archive=True)
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def _lookup_crc(self) -> List[PNG]:
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"""
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Look up PNG images in the database by their CRC value.
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def lookup_crc(png: PNG) -> List[PNG]:
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"""
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Look up PNG images in the database by their CRC value.
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Returns:
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List[PNG]: A list of PNG objects with matching CRC values, reconstructed from their
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packed representations.
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"""
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with app.app_context():
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imgs = IHDR.query.filter_by(crc=self.png.crc).all()
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results = []
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for img in imgs:
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packed = img.packed
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results.append(PNG.from_packed(packed, crc=self.png.crc))
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return results
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Args:
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png (PNG): A PNG object containing the CRC value to search for.
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def _search_height_crc(self) -> List[PNG]:
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"""
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Search for PNG images with matching CRC by iterating through possible heights.
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Returns:
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List[PNG]: A list of PNG objects with matching CRC values, reconstructed from their packed
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representations.
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"""
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with app.app_context():
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imgs = IHDR.query.filter_by(crc=png.crc).all()
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This function attempts to find alternative PNG configurations that produce the same
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CRC checksum as the input PNG by systematically varying the height parameter while
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keeping all other properties constant.
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Returns:
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List[PNG]: A list of PNG objects with matching CRC values. Returns an empty list
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if no matches are found.
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Note:
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The function iterates through heights from 100 to 3500 (inclusive).
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This may be computationally expensive for large ranges.
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"""
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results = []
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for img in imgs:
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packed = img.packed
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results.append(PNG.from_packed(packed, crc=png.crc))
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return results
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def search_height_crc(png: PNG) -> List[PNG]:
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"""
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Search for PNG images with matching CRC by iterating through possible heights.
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This function attempts to find alternative PNG configurations that produce the same
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CRC checksum as the input PNG by systematically varying the height parameter while
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keeping all other properties constant.
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Args:
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png (PNG): The reference PNG object whose CRC checksum will be matched.
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Returns:
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List[PNG]: A list of PNG objects with matching CRC values. Returns an empty list
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if no matches are found.
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Note:
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The function iterates through heights from 100 to 3500 (inclusive).
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This may be computationally expensive for large ranges.
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"""
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results = []
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for height in range(100, 3501):
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candidate = PNG(
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size=(png.width, height),
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bit_depth=png.bit_depth,
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color_type=png.color_type,
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interlace=png.interlace,
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)
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if candidate.crc == png.crc:
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results.append(candidate)
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return results
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def analyze_image_resize(input_img: Path, output_dir: Path) -> None:
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"""
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Analyze a PNG image and recover resized versions based on CRC matching.
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This function attempts to find matching image dimensions for a given PNG file
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by looking up its CRC (Cyclic Redundancy Check) in a database. If matches are
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found, it recovers and saves PNG images with the matched dimensions.
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Args:
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input_img (Path): Path to the input PNG image file to analyze.
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output_dir (Path): Path to the directory where recovered PNG images will be saved.
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Returns:
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None
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Raises:
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Handles exceptions gracefully by updating output data with error status.
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Side Effects:
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- Creates output directory if it doesn't exist.
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- Saves recovered PNG images to the output directory.
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- Updates data in the output directory with analysis results via update_data().
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Notes:
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- If the PNG has invalid structure or IHDR chunk is not first, an error is logged.
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- The function performs a two-step lookup: first by CRC, then by height/CRC if no matches
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found.
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- Recovered images are named as "recovered_{width}x{height}.png".
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- Analysis results (logs, status, and image URLs) are persisted via update_data().
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"""
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# 1. Setup Paths
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input_img = Path(input_img)
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output_dir = Path(output_dir)
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# 3. Initialize Logs
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logs = []
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try:
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with input_img.open("rb") as image:
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img_bytes = bytearray(image.read())
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try:
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png = PNG.from_bytearray(img_bytes)
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except ValueError:
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png = None
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if png is None:
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logs.append(
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"Failure: IHDR chunk is not the first chunk, or PNG has invalid structure."
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for height in range(100, 3501):
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candidate = PNG(
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size=(self.png.width, height),
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bit_depth=self.png.bit_depth,
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color_type=self.png.color_type,
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interlace=self.png.interlace,
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)
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update_data(
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output_dir,
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{
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"image_resize": {
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if candidate.crc == self.png.crc:
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results.append(candidate)
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return results
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def _write_recovered_png(self, png_bytes: bytearray, png_match: PNG) -> str:
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"""
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Rebuilds a PNG by patching IHDR width/height and writes it to disk.
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"""
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img_name = f"recovered_{png_match.width}x{png_match.height}.png"
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output_path = self.output_dir / img_name
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height_bytes = png_match.height.to_bytes(4, byteorder="big")
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width_bytes = png_match.width.to_bytes(4, byteorder="big")
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full_png_data = (
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png_bytes[:16] # Splicing: [Start...IHDR+4] + [W] + [H] + [IHDR+12...End]
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+ width_bytes
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+ height_bytes
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+ png_bytes[24:]
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)
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with output_path.open("wb") as out_f:
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out_f.write(full_png_data)
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return img_name
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def get_results(self, _: Optional[str] = None) -> dict[str, Any]:
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"""
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Analyze a PNG image and recover resized versions based on CRC matching.
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This function attempts to find matching image dimensions for a given PNG file
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by looking up its CRC (Cyclic Redundancy Check) in a database. If matches are
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found, it recovers and saves PNG images with the matched dimensions.
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Returns:
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None
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Raises:
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Handles exceptions gracefully by updating output data with error status.
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Side Effects:
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- Creates output directory if it doesn't exist.
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- Saves recovered PNG images to the output directory.
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- Updates data in the output directory with analysis results via update_data().
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Notes:
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- If the PNG has invalid structure or IHDR chunk is not first, an error is logged.
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- The function performs a two-step lookup: first by CRC, then by height/CRC if no
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matches found.
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- Recovered images are named as "recovered_{width}x{height}.png".
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- Analysis results (logs, status, and image URLs) are persisted via update_data().
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"""
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logs = []
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try:
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with self.input_img.open("rb") as image:
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img_bytes = bytearray(image.read())
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try:
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self.png = PNG.from_bytearray(img_bytes)
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except ValueError:
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return {
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"status": "error",
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"error": "IHDR chunk is not the first chunk, or PNG has invalid structure.",
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}
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},
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)
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return
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logs.append(f"Target CRC found: 0x{png.crc:08x}")
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# Already correct
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if self.png.crc == self.png.compute_crc():
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return {
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"status": "ok",
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"note": f"PNG is already valid with dimensions "
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f"{self.png.width}x{self.png.height} and crc 0x{self.png.crc:08x}.",
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}
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if png.crc == png.compute_crc():
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note = (
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f"PNG is already valid with dimensions {png.width}x{png.height} "
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f"and crc 0x{png.crc:08x}."
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)
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output_no_compute: dict[str, Any] = {
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"image_resize": {"status": "ok", "note": note}
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}
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update_data(output_dir, output_no_compute)
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return
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saved_img_urls = []
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saved_img_urls = []
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db_matches = lookup_crc(png)
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if not db_matches:
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db_matches = search_height_crc(png)
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if not db_matches:
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logs.append("Failure: No matching dimensions found.")
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else:
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# Create parent directories if they don't exist
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output_dir.mkdir(parents=True, exist_ok=True)
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# Iterate through ALL candidates found
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for im_match in db_matches:
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img_name = f"recovered_{im_match.width}x{im_match.height}.png"
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output_path = output_dir / img_name
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write_recovered_png(
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img_bytes, im_match.width, im_match.height, output_path
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)
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# No match found
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if not (db_matches := self._lookup_crc()) and not (
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db_matches := self._search_height_crc()
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):
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return {
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"status": "error",
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"error": "Failure: No matching dimensions found.",
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}
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# Match found, saving image(s)
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logs.append(f"Target CRC found: 0x{self.png.crc:08x}")
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self.output_dir.mkdir(parents=True, exist_ok=True)
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for png_match in db_matches:
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img_name = self._write_recovered_png(img_bytes, png_match)
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logs.append(f"Image saved: {img_name}")
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# Append the formatted URL to our list
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saved_img_urls.append("/image/" + str(Path(output_dir.name) / img_name))
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saved_img_urls.append("/image/" + str(Path(self.output_dir.name) / img_name))
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# 4. Final Data Update
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output_data: dict[str, Any] = {
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"image_resize": {
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return {
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"status": "ok",
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"output": logs,
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"png_images": saved_img_urls,
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}
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}
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update_data(output_dir, output_data)
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except Exception as e:
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return {"status": "error", "error": str(e)}
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except Exception as e:
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update_data(output_dir, {"image_resize": {"status": "error", "error": str(e)}})
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def analyze_image_resize(input_img: Path, output_dir: Path) -> None:
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"""Analyze an image submission using outguess."""
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analyzer = ResizeAnalyzer(input_img, output_dir)
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analyzer.analyze()
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@@ -89,12 +89,12 @@ def analyze_image(submission_hash: str) -> None:
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(analyze_decomposer, img_path, result_path),
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(analyze_exiftool, img_path, result_path),
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(analyze_foremost, img_path, result_path),
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(analyze_strings, img_path, result_path),
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(analyze_pngcheck, img_path, result_path),
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(analyze_steghide, img_path, result_path, submission.password),
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(analyze_openstego, img_path, result_path, submission.password),
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(analyze_zsteg, img_path, result_path),
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(analyze_image_resize, img_path, result_path),
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(analyze_openstego, img_path, result_path, submission.password),
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(analyze_pngcheck, img_path, result_path),
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(analyze_strings, img_path, result_path),
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(analyze_steghide, img_path, result_path, submission.password),
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(analyze_zsteg, img_path, result_path),
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]
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# Deep analysis only
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