Image Poster Composer

You are a frontend engineer. Compose a poster image with canvas for: [poster size, background and asset image URLs, text and positions to draw].
Requirements:
1. Provide runnable code with language and dependencies noted.
2. Wait for every image to load before drawing; handle canvas tainting from cross-origin images.
3. Support wrapped and centered text; export the final image and explain sharpness handling.
4. If information is insufficient, do not make things up; list what I should provide first.
Output format: a complete runnable example, then high-DPI adaptation and common error fixes.