Image Generation Guide

Learn how to write effective prompts, choose dimensions, and get the best results from Rendra's AI image generator.

Prompt Best Practices

The quality of your generated image is directly tied to the quality of your prompt. Here are the key principles:

Be specific and descriptive

Include the visual style, color palette, typography feel, mood, and composition you want. Generic prompts produce generic results.

"A dark-themed SaaS blog OG image with a purple-to-indigo gradient background, bold white sans-serif title text on the left, and a subtle grid pattern overlay. Professional and modern."

Don't

"A blog header image."

Mention the format context

Tell the AI what the image will be used for — social card, blog OG, product announcement banner. This helps set the right composition and hierarchy.

Specify colors and style

Reference colors by name or hex, and describe the style: minimalist, bold, corporate, playful, dark/light. The AI uses these signals to set the overall aesthetic.

Include text placement hints

If you want text in the image, describe where it should sit: "title text centered at the top", "website URL in the bottom-right corner", "logo in the top-left".

Tip: Rendra's AI performs best when you describe the visual result you want, not instructions for a person ("make the background purple" rather than "use CSS gradient #667eea to #764ba2").

Example Prompts

Blog Post OG

"A tech blog Open Graph image with a dark navy background, bold white serif headline placeholder, a thin purple accent line on the left, and a subtle code snippet watermark. Minimalist and professional."

Social Card

"A Twitter/X card for a developer tool launch. Vibrant purple-to-violet gradient, large bold product name in white, one-line tagline below in light gray, small icon top-right. Clean, high contrast."

Product Announcement

"Product launch announcement banner for a SaaS API. Dark background with glowing purple orb effect, 'Now in Beta' badge top-left, product name centered in large bold white text, abstract geometric shapes in the background."

Documentation Page

"Developer documentation page preview image. Clean white background, monospace code snippet on the right side, 'API Reference' title in dark sans-serif on the left, a green checkmark badge. Light and minimal."

Newsletter

"Weekly newsletter header image. Warm gradient from amber to orange, 'This Week in Tech' in large bold white text, subtle newspaper-column layout in the background. Energetic and readable."

Event / Webinar

"Webinar invite card. Deep blue background, abstract wave shapes, event title in bold white text, speaker name below in lighter weight, date badge in bright blue bottom-left. Modern and trustworthy."

Supported Dimensions

Rendra generates images at any custom dimension, but these are the most common OG image sizes:

Dimensions	Ratio	Use Case
`1200 × 630`	1.91:1	Facebook, LinkedIn, Open Graph standard
`1200 × 675`	16:9	Twitter/X large card, YouTube thumbnail
`1200 × 628`	~1.91:1	Facebook recommended
`1280 × 640`	2:1	Twitter summary card (legacy)
`800 × 418`	~1.91:1	Smaller OG, fast loading

Recommended: Start with 1200×630 — it works across all major social platforms and is the Open Graph standard.

Output Formats

PNG (default)

Lossless compression. Best for images with text, sharp edges, or transparency. Slightly larger file size than JPEG.

JPEG

Lossy compression. Smaller file sizes at the cost of some quality. Suitable for photographic or gradient-heavy images where small artifacts are acceptable.

Limites de débit

Rate limits are applied per API key, per rolling 60-second window:

Plan	Images / Month	Requests / Minute
Gratuit	50	5
Pro	1,000	30

When you hit a rate limit you'll receive a 429 Too Many Requests response with a Retry-After header indicating how many seconds to wait.

See Facturation et utilisation to upgrade your plan or check your current usage.