scraper_plan_v2.md

E-Waste Image Dataset Pipeline: Revised Plan (v2)

0. What changed from v1

v1 framed the work as a scraping problem. v2 treats it as a dataset-quality problem in which scraping is one input. The main changes:

Area	v1	v2
Class definitions	Scrape folders and annotation classes disagreed	One taxonomy defined first; queries derived from it
Deduplication	MD5 only (byte-identical)	Exact hash + perceptual hash (flip-aware) + embedding clusters, global across classes
Aspect-ratio filter	Discarded > 3:1 (removes RAM/edge-finger images)	Flag > 3:1, discard only > 6:1
Min resolution	250 px	Short side ≥ 480 px, long side ≥ 800 px
Relevance	None	CLIP zero-shot filter + manual review queue
Domain gap	Web images only	Real-world capture set, held-out real-world test split
Splits	Random train/val	Cluster-aware train/val + separate real-world test
Small objects	Not addressed	Resolution policy, imgsz=1280, tiling/two-stage inference
Image handling	verify() only, JPEG q90	verify() + load(), EXIF fix, alpha compositing, q95, originals preserved
Resilience	Claimed backoff/fallback that icrawler lacks	Custom downloader with retries, backoff, per-domain rate limits
Provenance	Sequential filenames	Hash filenames + SQLite manifest, resumable stages
Targets & metrics	None	Per-class image/instance targets, evaluation plan
BIS	Undefined	Proposed definition (needs sign-off)

---

1. Objective & Scope

Build a repeatable pipeline that produces a clean, deduplicated, well-documented image dataset for a YOLO detector that finds components on PCBs and supports an on-device Board Integrity Score (BIS) in a mobile app.

In scope: collection, validation, normalization, deduplication, relevance filtering, manifesting, splitting, annotation guidelines, training/evaluation plan, export. Out of scope for this document: app UI, backend, pricing/valuation logic beyond BIS inputs.

Success criteria

• ≥ 1,500 labeled images per class and ≥ 10,000 labeled instances per class in the training set (common YOLO guideline; revisit after the first training run).
• Zero train/val/test leakage (no near-duplicate or same-board pairs across splits).
• ≥ 40% of the final set is "in-the-wild" imagery (dirty, cluttered, phone-shot), not clean listing photos.
• Held-out real-world test set of ≥ 300 images that is never used for tuning.
• Every image traceable to its source URL, query, and processing history via the manifest.

---

2. Phase 0: Decisions to lock before writing code

2.1 Detection taxonomy (fixes the v1 class mismatch)

Define object classes (what YOLO detects) separately from image-level tags (metadata used for search and stratification).

Detection classes (v1 of the label set):

Class	Definition	Notes
cpu_socket	LGA, PGA, or ZIF processor socket footprint (populated or empty)	Sockets only; see BGA note below
gold_finger	Gold-plated edge-connector contacts (PCIe, RAM, edge cards)	Long, thin objects; boxes must not be forced square
ic_chip	Packaged ICs, including BGA-package chips soldered to the board	Optional sub-attribute bga in annotation tool
tantalum_capacitor	SMD tantalum capacitors (typically yellow/orange/black molded bodies with polarity bar)	Small object; needs labeling rules
desoldered_zone	Region with exposed pads/solder residue where a component was removed	Ambiguous; needs a precise definition and example gallery

BGA correction: BGA (ball grid array) is a chip package soldered onto the board. LGA/PGA are sockets. v1's bga_cpu_socket conflated them. In v2, BGA chips fall under ic_chip, and socket queries target LGA/PGA only.

Image-level tags (manifest metadata, not YOLO classes):

• board_type: desktop, laptop, phone, server, GPU, other
• condition: intact, stripped, burnt/damaged
• source_type: listing (white background), in_the_wild, recycling_yard, render/diagram (to be discarded)

Folders are not labels. Search-query hints are noisy and are stored only as class_hint metadata.

2.2 Target counts and attrition budget

Boards contain several classes per image, so ~3,000-4,000 unique labeled images may cover all classes, but the rare/small classes drive the budget.

Class	Target images	Target instances	Difficulty
ic_chip	1,500	15,000+	Easy (abundant)
cpu_socket	1,500	3,000+	Medium
gold_finger	1,500	5,000+	Medium
tantalum_capacitor	1,500	10,000+	Hard (small, visually varied)
desoldered_zone	1,500	5,000+	Hard (ambiguous)

Expect 50-70% attrition across validation, dedup, and relevance filtering, so plan to harvest roughly 3x the target (about 10,000-12,000 raw downloads). Set the exact harvest budget after a 500-image pilot measures the real attrition rate.

2.3 Board Integrity Score (BIS): proposed definition

BIS must be defined now because it determines which labels are needed.

Proposal (needs domain-owner sign-off):

V_present = Σ over detected high-value classes c of  w_c × count_c
            (cpu_socket, gold_finger, ic_chip, tantalum_capacitor)
V_missing = w_d × (number or area-normalized sum of desoldered_zone detections)

BIS = 100 × V_present / (V_present + V_missing)

Open questions: value weights w_c (need recycler input), whether to use counts or area, per-board-type normalization, and how detector confidence thresholds affect BIS stability. Log these as decisions in docs/decisions.md.

---

3. System Architecture

flowchart TD
    A["Config: taxonomy + query matrix"] --> B["URL harvest via icrawler: Bing / Baidu / Flickr"]
    B --> C["Resilient downloader: retry, backoff, rate limit"]
    RW["Real-world photo capture"] --> E
    C --> D[("Originals store: untouched bytes, sha256 names")]
    D --> E{"Validation"}
    E -- "fail: corrupt, under 20 KB, below min resolution, over 6:1" --> X["Discard and log reason"]
    E -- "pass (flag if over 3:1)" --> F["Normalize: EXIF fix, RGB, JPEG q95"]
    F --> G{"Dedup: exact + perceptual, global"}
    G -- "duplicate" --> X
    G -- "unique" --> H{"CLIP relevance filter"}
    H -- "irrelevant" --> X
    H -- "borderline" --> R["Manual review queue"]
    H -- "relevant" --> M["Manifest: SQLite"]
    R --> M
    M --> S["Cluster-aware split: train / val / test"]
    S --> L["Annotation: CVAT or Roboflow"]
    L --> T["YOLO training and evaluation"]

Design principles:

1. Stages are idempotent and resumable. Each image has a status in the manifest; reruns skip completed work.
2. Originals are never modified. Normalized copies are derived artifacts and can be regenerated with different settings.
3. Every discard is logged with a reason so thresholds can be tuned from data instead of guesses.

---

4. Directory & Dataset Schema

ewaste_dataset_pipeline/
├── scraper.py                  # CLI entry point (subcommands: harvest, validate, process, dedup, filter, split, report)
├── config/
│   ├── config.yaml             # thresholds, engines, rate limits, seeds
│   ├── taxonomy.yaml           # classes, definitions, image-level tags
│   └── queries.yaml            # query matrix (see §5.1)
├── pipeline/
│   ├── crawler.py              # URL harvest + custom downloader
│   ├── validator.py
│   ├── processor.py            # normalization
│   ├── dedup.py                # exact + perceptual + embedding clusters
│   ├── relevance.py            # CLIP zero-shot filter
│   ├── manifest.py             # SQLite state store + JSONL/CSV export
│   ├── split.py                # cluster-aware splitting
│   └── report.py               # summary statistics
├── tests/
│   ├── fixtures/               # truncated JPEG, RGBA PNG, EXIF-rotated, CMYK, animated GIF, 5:1 RAM image
│   └── test_*.py
├── data/
│   ├── originals/              # untouched downloaded bytes: <sha256[:16]>.<orig_ext>
│   ├── images/                 # normalized JPEGs: <sha256[:16]>.jpg (flat store)
│   ├── review/                 # borderline / flagged images for manual review
│   ├── realworld/              # own captures, organized by session_id
│   ├── manifest.db             # SQLite source of truth
│   └── manifest.jsonl          # export for tooling
├── splits/
│   └── splits.json             # frozen image_id -> split mapping (versioned)
├── reports/
│   └── summary.json
├── dataset_annotated/          # YOLO export after labeling
│   ├── data.yaml
│   ├── train/
│   ├── val/
│   └── test/                   # real-world sessions only
├── docs/
│   ├── decisions.md
│   └── labeling_guide.md
└── requirements.txt

The flat images/ store replaces per-class folders because one image can match several queries. Per-hint browsing views can be generated from the manifest on demand.

---

5. Core Modules

5.1 Query & Category Registry (queries.yaml)

Queries are derived from the taxonomy, then expanded along diversity axes. Two or three queries per class, as in v1, will not produce enough variety.

Expansion matrix: class term × board_type × condition × view/lighting × language

Axis	Example values
Board type	desktop motherboard, laptop mainboard, smartphone PCB, server board, GPU PCB
Condition	intact, stripped, burnt, corroded, dusty
View / setting	top view, close-up macro, angled, recycling bin, workbench, e-waste pile, hand-held
Language	English, plus Chinese, Spanish, German, Hindi, Vietnamese (recycling hubs and local marketplaces)

Example seed terms per class:

• cpu_socket: "LGA 1151 socket close up", "LGA 1700 socket bent pins", "PGA socket AM4 motherboard", "empty CPU socket motherboard scrap"
• gold_finger: "PCIe x16 gold fingers PCB", "RAM module gold contacts scrap", "edge connector gold plated board"
• ic_chip: "BGA chip on motherboard close up", "SMD IC laptop motherboard", "chipset heatsink removed motherboard"
• tantalum_capacitor: "SMD tantalum capacitor yellow PCB", "tantalum capacitor polarity stripe board", "tantalum capacitors recycling"
• desoldered_zone: "desoldered components exposed pads PCB", "cannibalized motherboard ewaste scrap", "hot air removed chips board", "burnt circuit board blowtorch"

Notes:

• Search engines cap results per query (often a few hundred at best), so volume comes from query variety, not from raising max_num.
• Record query, engine, and class_hint per URL in the manifest.

5.2 Harvesting & Download Engine (crawler.py)

• Engines: icrawler Bing, Baidu, and Flickr crawlers. The Google crawler is unreliable and optional. DuckDuckGo is not natively supported by icrawler and is removed from v1 scope; add it later only through a separate adapter.
• Two-step design:
  1. Use icrawler to harvest URLs and metadata into the manifest with status pending.
  2. A custom downloader (subclass of icrawler's ImageDownloader, or a requests session pool) performs the fetch.
• Resilience (implemented explicitly, since icrawler does not provide it):
  • Exponential backoff with jitter (e.g., tenacity), max 4 retries
  • Per-domain rate limiting and concurrency caps
  • Connect/read timeouts (e.g., 5s / 20s), maximum download size (e.g., 25 MB)
  • Content-Type and magic-byte sniffing before saving
  • Rotating realistic User-Agent strings
  • Respect HTTP 429 / Retry-After
• Concurrency: 4-8 downloader threads per query, global cap across queries.
• Resumability: URL-normalized dedup at the manifest level so reruns never re-fetch a URL already tried (successful or permanently failed).
• Storage: save untouched bytes to data/originals/ under <sha256[:16]>.<ext>.

5.3 Validation Engine (validator.py)

Checks run in a fixed order so cheap checks fail first:

#	Check	Rule	Action
1	File size	< 20 KB	Discard (too_small_file)
2	Integrity	Image.open() → verify() → reopen → load() (catches truncation that verify() misses)	Discard (corrupt)
3	Animated	Multi-frame GIF/WEBP	Use first frame; flag animated
4	Resolution	Short side < 480 px or long side < 800 px	Discard (low_resolution)
5	Aspect ratio	> 3:1 or < 1:3	Flag extreme_aspect, send to review
6	Aspect ratio (hard)	> 6:1 or < 1:6	Discard (extreme_aspect_hard)

Why the aspect-ratio change: RAM modules and edge-finger crops are naturally ~4.5-5:1. A 3:1 hard cutoff would remove exactly the images the gold_finger class needs.

Why the resolution change: tantalum capacitors and desoldered zones occupy very few pixels; a 250 px image contains almost no usable detail for them.

5.4 Normalization Engine (processor.py)

Applied to a copy of each validated image:

1. ImageOps.exif_transpose() first, so phone photos are not rotated incorrectly.
2. Mode conversion to RGB:
   • RGBA / LA / P-with-transparency: composite onto a white background (a naive convert("RGB") turns transparency black).
   • CMYK: convert via embedded ICC profile when present (ImageCms), otherwise standard conversion.
   • Grayscale: replicate to 3 channels.
3. Size cap: if the long side > 2560 px, downscale with LANCZOS (never upscale). This bounds storage while preserving detail for small objects.
4. Encode: JPEG quality 95, 4:4:4 chroma subsampling (subsampling=0), optimize=True. This limits the extra lossy generation and keeps fine solder/pad detail that q90 with default 4:2:0 would blur.
5. Metadata: strip EXIF (privacy and size); store dimensions and original format in the manifest.
6. Output name: data/images/<sha256[:16]>.jpg, where the hash is of the original file bytes.

5.5 Deduplication Engine (dedup.py)

MD5 catches only byte-identical files. A resized or recompressed copy of the same photo gets a different hash, and near-duplicates that straddle train/val inflate metrics. v2 uses three layers, applied globally across all classes and all queries:

Layer	Method	Catches
1. Exact	SHA-256 of original bytes (pre-decode) and of decoded pixel array	Byte-identical and re-saved-identical images
2. Near-duplicate	Perceptual hash (imagehash pHash, 64-bit, plus dHash) with Hamming distance ≤ 6; also hash the horizontally flipped image and compare	Resizes, recompression, minor crops/edits, mirror copies
3. Semantic clusters	CLIP image embeddings; cosine similarity ≥ 0.95 → same cluster (agglomerative or connected components)	Same board photographed from slightly different angles, same listing series

Implementation notes:

• For ≤ 100k images, pairwise Hamming comparison with vectorized NumPy popcount is fast enough; use a BK-tree or LSH banding beyond that.
• Within a duplicate group, keep the highest-resolution member and record all members' URLs under it in the manifest.
• Every image gets a cluster_id. Layers 1-2 remove images; layer 3 does not remove images, it only labels clusters for leakage-safe splitting (§6).

5.6 Relevance Filter (relevance.py)

Search results contain many stock illustrations, renders, diagrams, product boxes, logos, and off-topic hardware.

• Model: open_clip (e.g., ViT-B/32) zero-shot scoring.
• Positive prompts: "a photo of a printed circuit board", "a photo of a computer motherboard", "a photo of electronic waste".
• Negative prompts: "a 3D render", "a diagram or schematic", "a product box", "a logo", "a screenshot", "a computer case", "a person", "an image with a watermark".
• Buckets: relevant (auto-keep), borderline (manual review), irrelevant (discard). Tune the two thresholds on a hand-labeled sample of ~200 images, then report precision/recall of the filter.
• source_type tagging: use zero-shot prompts to estimate listing vs in_the_wild so the domain mix can be monitored.
• Watermarks/stock: flagged, not auto-discarded (zero-shot watermark detection is unreliable). Flagged images go to review.

5.7 Manual Review

• Review all borderline and extreme_aspect items, plus a 10% random sample of auto-kept images to estimate residual noise.
• Use a contact-sheet tool (FiftyOne or a simple generated HTML grid) that supports keep/discard/re-tag.
• Record reviewer decisions in the manifest (review_status, reviewer, reviewed_at).

5.8 Manifest & Provenance (manifest.py)

SQLite is the source of truth, exported to JSONL/CSV for tooling. One row per image (plus a table of source URLs per image).

Field	Description
image_id	sha256[:16] of original bytes
source_urls[]	all URLs that produced this image
engine, queries[], class_hints[]	how it was found
scraped_at	timestamp
orig_format, width, height, filesize, aspect_ratio	measured properties
flags[]	extreme_aspect, animated, watermark_suspect, etc.
phash, dhash	perceptual hashes
cluster_id	duplicate/semantic cluster
clip_score, relevance_bucket	filter outputs
board_type, condition, source_type	image-level tags
status	pending → downloaded → validated → normalized → deduped → filtered → kept or discarded
discard_reason	why it was removed
review_status	reviewer outcome
split	train / val / test (set by §6)
session_id, board_id	for real-world captures

---

6. Real-World Data & Splitting

6.1 Real-world capture set (closes the domain gap)

Web results skew toward clean listing photos. The deployed app will see dirty, cluttered, phone-shot boards under poor lighting.

• Capture ≥ 300 test images plus ≥ 300 additional training images from recycling partners or a bench setup.
• Vary: phone models, lighting (daylight, warm, harsh flash, dim), backgrounds, distances (macro to whole-board), angles, board types, and conditions.
• Record session_id (one per visit/location/day) and board_id (one per physical board). Photograph each board from multiple angles.
• Capture at native phone resolution; keep originals.

6.2 Split policy (leakage-safe)

Split	Composition	Rule
train	Web + real-world training sessions	~80% of the non-test pool
val	Web + real-world training sessions	~20% of the non-test pool; used for model selection
test	Real-world sessions only, held out	Never used for tuning or threshold selection; sessions not present in train/val

• Split by group, not by image: use cluster_id for web images and board_id/session_id for real-world images (GroupShuffleSplit or similar), so near-duplicates and same-board photos never straddle splits.
• Stratify on class_hints and source_type where feasible so val reflects the domain mix.
• Freeze the result in splits/splits.json with the random seed; regenerate only by explicit version bump.

---

7. Annotation

• Write docs/labeling_guide.md before labeling: definitions and 10+ positive/negative example crops per class, plus edge cases (partially occluded, damaged, blurry).
• Label at full resolution (never label downscaled copies).
• Minimum object size policy: objects smaller than ~16 px at the intended training resolution are either marked ignore or excluded consistently; document the choice.
• Boxes: tight; gold_finger boxes follow the actual (elongated) strip; no padding to squares.
• Quality control: double-annotate a 10% sample, compute IoU/agreement per class, and resolve disagreements to refine the guide. desoldered_zone is the class most likely to need a redefinition.
• Tools: CVAT or Roboflow. Export in YOLO format with the frozen splits.

---

8. Training & Evaluation Plan

8.1 Small-object strategy

• Train with imgsz=1280 (or 960 as a compromise) rather than the 640 default.
• For on-device use, avoid running the full nano model at 1280 on a phone. Two options to evaluate:
  1. Tiled inference (SAHI-style): overlapping 640 px tiles with merged detections.
  2. Two-stage: a light board detector at 640 → crop board → component detector on the crop.
• Consider mosaic/scale augmentation tuned for small objects; verify augmentations do not destroy gold_finger aspect ratios.

8.2 Metrics

• mAP@50 and mAP@50-95 per class, not just overall.
• Recall by object-size bucket (small / medium / large by pixel area), to expose the small-object problem.
• Report results on val and, separately, on the real-world test split. The test-set number is the headline number.
• BIS validation: compare BIS from ground-truth labels vs BIS from detections on the test set, and report the error.

8.3 Export checks

• Export to ONNX / TFLite and re-evaluate on the test set after export and after quantization; set an acceptable mAP-drop budget (e.g., ≤ 2 points) before shipping to mobile/.

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9. Technical Stack

Tool / Library	Role
Python 3.10+	Runtime
icrawler	URL harvesting (Bing, Baidu, Flickr; Google optional)
requests, tenacity	Custom downloader with retry/backoff
Pillow	Validation, EXIF handling, normalization, ICC conversion
numpy	Vectorized hash comparison
imagehash	Perceptual hashing (pHash/dHash)
hashlib	Exact SHA-256 hashing
open_clip_torch + torch	Relevance filter and embeddings for clustering
scikit-learn	Group-aware splitting, clustering
PyYAML	Configuration
tqdm	Progress monitoring
fiftyone (optional)	Review UI, embedding visualization
ultralytics, sahi	Training and tiled inference
pytest	Tests

Pin exact versions in requirements.txt and record them in every report.

---

10. Execution Plan

Step 1: Install

pip install -r requirements.txt

Step 2: Run stages (each is resumable)

python3 scraper.py harvest   --config config/config.yaml   # collect URLs into manifest
python3 scraper.py download                                 # fetch originals with retries
python3 scraper.py validate                                 # integrity, size, aspect
python3 scraper.py process                                  # EXIF fix, RGB, JPEG q95
python3 scraper.py dedup                                    # exact + perceptual + clusters
python3 scraper.py filter                                   # CLIP relevance + review queue
python3 scraper.py split                                    # cluster-aware splits
python3 scraper.py report                                   # summary statistics

Step 3: Verification report (reports/summary.json and printed table)

Per class_hint and overall:

• Raw URLs harvested, downloads succeeded/failed
• Discards by reason (corrupt, too small, low resolution, hard aspect, exact dup, near dup, irrelevant)
• Flagged and reviewed counts
• Final kept count vs target (§2.2)
• Resolution distribution and source_type mix (in-the-wild share vs the 40% goal)
• Number of duplicate clusters and largest cluster size
• Split sizes and a leakage check (no cluster_id/board_id shared across splits)

---

11. Testing

Unit tests using fixtures in tests/fixtures/:

Test	Expectation
Truncated JPEG	Rejected by the verify() + load() sequence
RGBA PNG with transparency	Composited on white, not black
EXIF-rotated phone photo	Output is upright
CMYK JPEG	Correct RGB conversion
Animated GIF	First frame used, animated flag set
5:1 RAM image	Flagged, not discarded
8:1 banner	Discarded with extreme_aspect_hard
Resized / recompressed / flipped copy of a fixture	Detected as near-duplicate
Rerun after interruption	No re-download, no duplicate rows
Leakage check	No shared cluster_id across splits

---

12. Milestones & Acceptance Criteria

Phase	Deliverable	Acceptance criterion
0. Decisions	taxonomy.yaml, target counts, BIS definition in docs/decisions.md	Signed off by project owner
1. Pipeline build	All modules + tests passing	Fixtures behave as specified in §11
2. Pilot	~500-image end-to-end run	Attrition rate measured; CLIP thresholds tuned on 200 hand-labeled images
3. Full collection	Harvest budget executed; real-world capture ≥ 600 images	Kept counts meet §2.2 or gaps identified and queries extended
4. QA	Manual review complete; frozen splits.json	Leakage check clean; ≥ 40% in-the-wild
5. Annotation	Labeled dataset + labeling_guide.md	Inter-annotator agreement acceptable per class
6. Training & eval	Baseline model, per-class and size-bucket metrics	Test-set results reported; failure analysis written
7. Export	ONNX/TFLite + post-quantization test results	mAP drop within budget; BIS error reported

---

13. Risks & Mitigations

Risk	Mitigation
Search engines return too few unique images per query	Wide query matrix (§5.1), multiple engines, multilingual queries, real-world capture
Heavy overrepresentation of clean listing photos	source_type monitoring; explicit in-the-wild target; real-world capture
Tiny objects (tantalum caps) undetectable	Higher min resolution, imgsz=1280, tiling/two-stage, small-object metrics
desoldered_zone label ambiguity	Precise definition, example gallery, double annotation, willingness to redefine or move to segmentation
Near-duplicate leakage inflates metrics	Cluster-aware splits, leakage check in CI, held-out real-world test set
CLIP filter discards valid images	Threshold tuned on hand-labeled sample; borderline goes to review, not discard
Class imbalance (ICs abundant, tantalum rare)	Per-class targets, targeted queries and captures for rare classes, per-class metrics
Quantization degrades small-object accuracy	Post-export evaluation with a mAP-drop budget; consider mixed precision
Pipeline state lost mid-run	SQLite manifest, idempotent stages, originals preserved
BIS unstable or not meaningful	Define and validate BIS against ground-truth labels early (§2.3, §8.2)

---

14. Immediate Next Actions

1. Review and finalize the taxonomy and class definitions (§2.1).
2. Get domain input on BIS weights and whether BIS uses counts or area (§2.3).
3. Stand up the repository skeleton from §4, with config, manifest schema, and test fixtures.
4. Run the 500-image pilot to measure attrition and tune the relevance thresholds.
5. Schedule the first real-world capture session so the test set starts accumulating early.