Alt Text Batch Generator

Batch-process multiple images to generate AI-powered alt text descriptions for web accessibility using Qwen2.5-VL vision model.

Overview

This Actor processes up to 500 images in a single run and generates alt text descriptions suitable for screen readers and accessibility compliance. Each successfully processed image is charged at $0.01 (pay-per-event pricing).

Key Features

• Batch Processing: Process up to 500 images per run
• AI-Powered: Uses Qwen2.5-VL vision model via ntriq AI service
• Flexible Output: Choose between concise (WCAG-compliant max 125 chars) or detailed (2-3 sentence) descriptions
• Multi-Language: Supports 10 languages (English, Korean, Japanese, Chinese, Spanish, French, German, Italian, Portuguese, Russian)
• Pay-Per-Event: Only pay $0.01 for successfully processed images
• Error Resilience: Continues processing even if individual images fail
• Detailed Logging: Track processing time and confidence scores per image

Input

Provide an array of publicly accessible image URLs:

{
  "urls": [
    "https://example.com/image1.jpg",
    "https://example.com/image2.png",
    "https://example.com/image3.webp"
  ],
  "language": "en",
  "style": "concise",
  "maxUrls": 500
}

Input Parameters

Parameter	Type	Default	Required	Description
urls	array	—	✓	Array of image URLs (1-500 items)
language	string	en	—	Language code: en, ko, ja, zh, es, fr, de, it, pt, ru
style	string	concise	—	Output style: concise (≤125 chars) or detailed (2-3 sentences)
maxUrls	integer	500	—	Safety limit on processing count (1-500)

Output

Each image produces one dataset record:

{
  "url": "https://example.com/image1.jpg",
  "status": "success",
  "altText": "A fluffy orange tabby cat sitting on a wooden windowsill",
  "detailedDescription": null,
  "language": "en",
  "model": "Qwen2.5-VL",
  "processingTimeMs": 2450,
  "confidence": 0.85,
  "error": null,
  "code": null
}

Output Fields

Field	Type	Description
url	string	Original image URL
status	string	success or error
altText	string	Generated alt text (concise style)
detailedDescription	string|null	Detailed description (detailed style only)
language	string	Output language code
model	string	AI model name (Qwen2.5-VL)
processingTimeMs	integer	Processing time in milliseconds
confidence	number	AI confidence score (0-1)
error	string|null	Error message if failed
code	string|null	Error code: INVALID_URL, TIMEOUT, API_ERROR, etc.

Usage Examples

Example 1: Basic Batch Processing (English, Concise)

{
  "urls": [
    "https://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Cat03.jpg/1200px-Cat03.jpg",
    "https://upload.wikimedia.org/wikipedia/commons/thumb/1/18/Dog_Breeds.jpg/1200px-Dog_Breeds.jpg"
  ],
  "language": "en",
  "style": "concise"
}

Cost: $0.02 (2 images × $0.01)

Example 2: Large Batch with Detailed Descriptions (Korean)

{
  "urls": [
    "https://example.com/image1.jpg",
    "https://example.com/image2.jpg",
    "https://example.com/image3.jpg",
    "...up to 500 images..."
  ],
  "language": "ko",
  "style": "detailed",
  "maxUrls": 500
}

Cost: $0.03 - $5.00 depending on successes (1-500 images × $0.01)

Pricing

• $0.01 per successfully generated alt text
• Only charged on success (errors don't incur charges)
• No upfront cost for batch size
• Apify platform fee applies (20% of generation cost)

Cost Examples

Images	Success	Cost
10	10	$0.10
50	48 (2 failed)	$0.48
100	95 (5 failed)	$0.95
500	500	$5.00

Timeout & Rate Limiting

• Per-image timeout: 30 seconds
• Batch timeout: Apify default (6 hours for standard run)
• Rate limit: 100ms delay between requests (built-in throttling)

Error Codes

Code	Meaning	Recovery
INVALID_INPUT	Missing/invalid URL parameter	Check URL format
INVALID_URL	URL not HTTP(S) or malformed	Verify URL is valid and public
TIMEOUT	Request exceeded 30 seconds	Image too large or service overloaded
API_ERROR	AI service returned error	Check service status
PROCESSING_ERROR	Other processing failure	Check image format/size
EXCEPTION	Unhandled exception	Contact support

Legal Notice

Image Source Responsibility

• You must only submit images that you own or have explicit permission to analyze.
• You are responsible for complying with the source website's Terms of Service and robots.txt.
• Do not use this tool to analyze images from stock photo sites (Getty, Shutterstock) without a valid license.

Copyright

• Generated alt text descriptions are not derivative works of the original images.
• However, fetching images from third-party URLs may violate the source site's Terms of Service.
• We assume no liability for third-party intellectual property claims arising from your use.

WCAG Compliance

• AI-generated alt text is a starting point, NOT a guarantee of WCAG 2.1 or ADA compliance.
• All generated descriptions must be reviewed by a human before production use.
• This tool assists accessibility efforts but does not replace professional accessibility auditing.

AI Limitations

• Descriptions may contain inaccuracies or miss important context.
• Specialized images (medical, technical, charts) require professional review.

Data Processing

• Images are fetched temporarily for analysis and immediately discarded.
• No images are stored, cached, or redistributed by our service.

Technical Details

AI Service Integration

• Endpoint: https://ai.ntriq.co.kr/analyze/image (Qwen2.5-VL)
• Request Timeout: 30 seconds per image
• Supported Formats: JPEG, PNG, WebP, GIF, BMP
• Max Image Size: Depends on AI service (typically 100MB)

Environment Variables (Optional)

AI_API_ENDPOINT=https://ai.ntriq.co.kr/analyze/image
AI_REQUEST_TIMEOUT=30000

Processing Pipeline

1. Validate input array and language/style parameters
2. For each URL:
   • Validate URL format
   • Call AI service with optimized prompt
   • Collect response (alt text or error)
   • Push to dataset
   • Charge on success
3. Log summary (success/error counts, total cost)

Limitations

Limitation	Value
Max images per run	500
Timeout per image	30 seconds
Total batch timeout	6 hours (Apify default)
Concurrent requests	Sequential (100ms between)
Supported formats	JPEG, PNG, WebP, GIF, BMP

Support

For issues or questions:

1. Check error codes and logs in run output
2. Verify all image URLs are publicly accessible
3. Confirm language code is supported
4. Review AI service status

Version History

• v1.0.0 (2026-03-30): Initial release
  • Batch processing (up to 500 images)
  • Concise and detailed styles
  • Multi-language support
  • Pay-per-event billing

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Last Updated: 2026-03-30 Maintainer: ntriq Engineering License: Apache 2.0