Auction Item Image Analysis Reference

Use this skill when working on image analysis features, Claude Vision prompts, or photo-based cataloging. Focus on: $ARGUMENTS

How Image Analysis Works in the Extension

Architecture

Item images (up to 5 slots) → base64 encoding → Claude Vision API
                                                      ↓
                                               Structured JSON response:
                                               - Title, description, condition
                                               - Artist, period, materials
                                               - Keywords, estimate, reserve

Image Slots (categorized)

Image Processing

• Images exceeding 5MB auto-resized via canvas (_resizeBase64Image)
• Max dimension: 1400px (progressively reduced if still too large)
• Output: JPEG at 0.82 quality (reduced to 0.5 at minimum)
• Domain whitelist: auctionet.com, images.auctionet.com, upload.wikimedia.org

What to Look For (by category)

Art & Paintings

• Signature: location (lower right, a tergo), legibility, full name vs initials
• Dating: exact year, decade, century — write exactly as on work
• Technique: oil on canvas, watercolor, mixed media, lithograph, etching
• Numbering: edition number for prints (e.g., "120/310")
• Frame: type, period (but NEVER report frame condition)
• Canvas/paper: condition, foxing, tears, restorations
• Size: height × width without frame

Furniture

• Style identification: gustavian, rococo, art deco, functionalist
• Construction: joinery type, original vs restored parts
• Wood type: visible in unfinished areas — only identify if confident
• Hardware: original vs replacement handles, locks, hinges
• Surface: veneer condition, inlay, painted decoration
• Stamps/labels: maker marks, often on underside or back

Silver & Gold

• Hallmarks: city mark, year mark, maker mark, assay mark
• Purity: sterling (925), 830, 18k, 14k — only from stamps, never guess
• Weight: essential for precious metals
• Engravings: monograms, presentation inscriptions (always mention in condition)
• Construction: filled base vs solid (affects weight relevance)

Glass & Ceramics

• Manufacturer marks: underside stamps, etched signatures
• Technique: blown, pressed, cut, etched, overlay
• Color: describe accurately for glass
• Condition: chips (nagg), hairline cracks (hårspricka), crazing
• Size: height and/or diameter

Rugs & Textiles

• Origin: Persian, Turkish, Scandinavian — from patterns and construction
• Construction: hand-knotted, machine-made, flatweave
• Material: wool, silk, cotton — from texture and sheen
• Condition: fringe wear, color fading, repairs, moth damage
• Size: always in title — length × width

Watches & Clocks

• Manufacturer & model: from dial and caseback
• Movement: automatic vs quartz (from caseback or movement view)
• Case material: steel, gold, gold-plated — from stamps
• Case size: diameter in mm
• Dial condition: patina, lume condition, text legibility

Weapons & Militaria

• EXTRA CAUTION — anti-hallucination rules are strictest here
• Only describe what is physically visible
• Never add historical context not explicitly present
• Never guess school names, regions, or periods from style
• Focus on: markings, inscriptions, materials, construction method

AI Prompt Patterns for Image Analysis

Hallucination Prevention

• "Describe ONLY what you can see in the image"
• "Do NOT infer historical period from style alone"
• "If uncertain about material, say 'appears to be' not 'is'"
• "Never fabricate maker names, dates, or provenance"

Extraction Priority

1. Object identification — what is it?
2. Material identification — what's it made of?
3. Maker/artist identification — who made it? (from visible marks only)
4. Condition assessment — what damage/wear is visible?
5. Period estimation — when was it made? (conservative)
6. Valuation clues — quality level, rarity indicators

Multi-Image Strategy

When multiple images are available:

• Cross-reference front view with detail shots
• Use back/underside for construction clues
• Use marking photos to confirm or identify maker
• Use condition photos to quantify damage described in main view
• Don't repeat information already captured from another image

Photography Guidelines (for reference)

Minimum Standards

• At least 3 photos per item
• Clean, neutral background (NCS S4000 N gray)
• Even lighting, no harsh shadows
• Include scale reference where helpful

Category-Specific Photo Requirements