From c81d3e6d3da0963fd28371aee8c72a5a74c5c9ce Mon Sep 17 00:00:00 2001 From: Philip Zimmermann Date: Tue, 9 Dec 2025 16:07:10 +0100 Subject: [PATCH] Added automatic PNG resizing solver --- aperisolve/analyzers/image_resize.py | 189 +++++++++++++++++++++++++++ 1 file changed, 189 insertions(+) create mode 100644 aperisolve/analyzers/image_resize.py diff --git a/aperisolve/analyzers/image_resize.py b/aperisolve/analyzers/image_resize.py new file mode 100644 index 0000000..a0710db --- /dev/null +++ b/aperisolve/analyzers/image_resize.py @@ -0,0 +1,189 @@ +"""Image size bruteforcer for common PNG sizes.""" + +import zlib +from pathlib import Path +from .utils import update_data + +# Full list of expected sizes +EXPECTED_SIZES = [ + # ------------------------- + # ICONS (Square) + # ------------------------- + (16, 16), (20, 20), (24, 24), (28, 28), + (32, 32), (48, 48), (64, 64), (72, 72), + (96, 96), (128, 128), (192, 192), (256, 256), + (384, 384), (512, 512), (768, 768), (1024, 1024), + (1536, 1536), (2048, 2048), (4096, 4096), + + # ------------------------- + # 1:1 Square (General) + # ------------------------- + (300, 300), (500, 500), (800, 800), (1000, 1000), + (1500, 1500), (2000, 2000), (2500, 2500), (3000, 3000), + + # ------------------------- + # 4:3 Aspect (Classic Screens) + # ------------------------- + (320, 240), (640, 480), (800, 600), (960, 720), + (1024, 768), (1280, 960), (1600, 1200), (2048, 1536), + (2560, 1920), (3200, 2400), (4096, 3072), + + # ------------------------- + # 3:2 Aspect (Photography) + # ------------------------- + (600, 400), (900, 600), (1200, 800), (1500, 1000), + (1800, 1200), (2400, 1600), (3000, 2000), (3600, 2400), + (4500, 3000), (6000, 4000), + + # ------------------------- + # 16:9 Aspect (Video / Web) + # ------------------------- + (426, 240), (640, 360), (854, 480), (960, 540), + (1280, 720), (1366, 768), (1600, 900), (1920, 1080), + (2560, 1440), (3200, 1800), (3440, 1935), (3840, 2160), + (5120, 2880), (7680, 4320), (10240, 5760), + + # ------------------------- + # 16:10 Aspect (Laptops) + # ------------------------- + (1280, 800), (1440, 900), (1680, 1050), + (1920, 1200), (2560, 1600), (2880, 1800), + (3840, 2400), (5120, 3200), + + # ------------------------- + # Mobile Portrait (9:16) + # ------------------------- + (720, 1280), (1080, 1920), (1440, 2560), + (2160, 3840), (1440, 2960), (1080, 2400), + (1170, 2532), (1284, 2778), (1290, 2796), + + # ------------------------- + # Social Media Sizes + # ------------------------- + # Instagram + (1080, 1080), (1080, 1350), (1080, 1920), + + # Facebook + (1200, 628), (1200, 1200), + + # Twitter/X + (1200, 675), (1500, 500), + + # YouTube Thumbnails + (1280, 720), (1920, 1080), + + # ------------------------- + # Banners / Headers + # ------------------------- + (1600, 500), (1920, 500), (2560, 700), + (3000, 1000), (3840, 1200), + + # ------------------------- + # Print-like Digital Sizes + # ------------------------- + (2550, 3300), # Letter @ 300 DPI + (2480, 3508), # A4 @ 300 DPI + (3508, 4961), # A3 @ 300 DPI + (4961, 7016), # A2 @ 300 DPI + (7016, 9933), # A1 @ 300 DPI + +] + +def calc_checksum(header_chunk, width_bytes, height_bytes): + """ + Calculates the CRC32 of the IHDR chunk with new dimensions. + header_chunk: The full IHDR chunk (Type + Data). + """ + # Reconstruct IHDR: [Type(4)] + [New Width(4)] + [New Height(4)] + [Rest of Data(5)] + new_header = header_chunk[:4] + width_bytes + height_bytes + header_chunk[12:] + + # Calculate CRC and return as 4 bytes (Big Endian) + return bytearray((zlib.crc32(new_header) & 0xffffffff).to_bytes(4, byteorder='big')) + +def analyze_image_resize(input_img: Path, output_dir: Path) -> None: + """ + Analyze an image submission using python-based resize bruteforce. + Attempts to recover PNGs with modified resolutions but valid CRCs. + """ + + # 1. Setup Paths + input_img = Path(input_img) + output_dir = Path(output_dir) + extracted_dir = output_dir / "image_resize_output_dir" + + # 2. CREATE THE DIRECTORY (Crucial Step!) + extracted_dir.mkdir(parents=True, exist_ok=True) + + # 3. Initialize Logs + logs = [] + recovered_images = [] + + try: + with open(input_img, "rb") as image: + f = image.read() + b = bytearray(f) + + # Find IHDR start + IHDR = b.find(b'\x49\x48\x44\x52') + if IHDR == -1: + logs.append("Failure: PNG header (IHDR) not found.") + update_data(output_dir, {"image_resize": {"status": "error", "error": "PNG header not found."}}) + return + + # Calculate Chunk Length (The 4 bytes BEFORE IHDR tag) + chunk_length = int.from_bytes((b[IHDR- 4: IHDR]), byteorder="big") + 4 + + # Extract Target CRC (The 4 bytes AFTER the chunk data) + target_crc = b[IHDR + chunk_length:IHDR + chunk_length + 4] + + # Isolate the header chunk (Type + Data) + header_chunk = b[IHDR:IHDR + chunk_length] + + logs.append(f"Target CRC found: 0x{target_crc.hex()}") + + match_found = False + + # Brute-force Loop + for size in EXPECTED_SIZES: + width, height = size + + # Convert dimensions to 4-byte Big Endian arrays + width_bytes = bytearray(width.to_bytes(4, byteorder='big')) + height_bytes = bytearray(height.to_bytes(4, byteorder='big')) + + # Check if this size matches the file's CRC + if target_crc == calc_checksum(header_chunk, width_bytes, height_bytes): + match_found = True + logs.append(f"Success: Match found! Dimensions: {width}x{height}") + + # Create Output Filename + output_filename = f"recovered_{width}x{height}.png" + output_path = extracted_dir / output_filename + + # Splicing: [Start...IHDR+4] + [W] + [H] + [IHDR+12...End] + full_png_data = b[:IHDR+4] + width_bytes + height_bytes + b[IHDR+12:] + + # Write the recovered file to disk + with open(output_path, "wb") as out_f: + out_f.write(full_png_data) + + recovered_images.append(output_filename) + break # Stop looking after finding the match + + if not match_found: + logs.append("Failure: No matching dimensions found.") + + # 4. Final Data Update + output_data = { + "image_resize": { # Key name must match your module name in AperiSolve + "status": "ok", + "output": logs, + "images": recovered_images, # Tells frontend to display the image + } + } + update_data(output_dir, output_data) + + except Exception as e: + update_data(output_dir, {"image_resize": {"status": "error", "error": str(e)}}) + + return None \ No newline at end of file