Tokenization guide

Documentation Index

Fetch the complete documentation index at: https://docs.perceptron.inc/llms.txt

Use this file to discover all available pages before exploring further.

Understand how Isaac 0.2 counts tokens for images so you can estimate costs and optimize preprocessing pipelines.

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Image Token Counting

The gateway smart-resizes any image whose native patch count exceeds the 6,144-patch cap before tokenization, preserving aspect ratio. Isaac 0.2 (both 1B and 2B Preview) uses a patch-based image tokenizer:

• Native resolution: Processes images at their original resolution; supports a wide range of aspect ratios.
• Patch size: 16 × 16 pixels.
• Spatial merge size: 2 × 2 (4 patches into a single token).
• Token formula: ⌈width / 32⌉ × ⌈height / 32⌉.
• Minimum: 256 patches → 64 tokens (smaller images auto-upscaled).
• Maximum: 6,144 patches → ~1,508 tokens for 16:9 inputs (resized dimensions must be divisible by 32, so the practical ceiling is ~1,508 tokens).
• Smart-resize is silent: no warning in the response. To keep deterministic control over input quality, pre-resize client-side before uploading.

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Calculation Examples

Example 1: 640×480 (VGA) — No Resize Needed

1. Round dimensions to nearest multiple of 32: 640×480 (already divisible).
2. Calculate patches: (640 ÷ 16) × (480 ÷ 16) = 40 × 30 = 1,200 patches.
3. Calculate tokens: 1,200 patches ÷ 4 = 300 tokens.
4. Check constraints: 256 ≤ 1,200 ≤ 6,144 ✓ (no resize needed).
5. Cost (Isaac 0.2 at $0.15/M input): 300 × ($0.15 / 1,000,000) = $0.000045.

Example 2: 1920×1080 (Full HD) — Requires Resize

1. Calculate original patches: (1920 ÷ 16) × (1080 ÷ 16) = 120 × 68 = 8,160 patches.
2. Check constraints: 8,160 > 6,144 (exceeds maximum, resize needed).
3. Resize to 1664×928 (maintains ~16:9 aspect ratio, divisible by 32).
4. Calculate new patches: (1664 ÷ 16) × (928 ÷ 16) = 104 × 58 = 6,032 patches.
5. Calculate tokens: 6,032 patches ÷ 4 = 1,508 tokens.
6. Cost (Isaac 0.2 at $0.15/M input): 1,508 × ($0.15 / 1,000,000) = $0.000226.

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Constraints

• Context window: 8K tokens (image + text + reasoning + answer all share the same budget).
• Supported MIME types: image/png, image/jpeg, image/webp.

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Pricing

Pricing for Isaac 0.2 (both 1B and 2B Preview):

• Input: $0.15 per million tokens ($0.15/MT)
• Output: $1.25 per million tokens ($1.25/MT)

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Common Image Sizes

Token counts and costs for common image resolutions.

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Optimization Guidance

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Recommended Resolutions

We recommend passing in the original resolution of the image. If the resolution is greater than the maximum supported, we recommend client-side preprocessing. Lower resolution can erode quality but may improve latency and reduce token counts.

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Client-Side Preprocessing

You can resize images before sending them to reduce token usage and costs: When to Resize:

• Below minimum: If your images are smaller than 256 patches, resize them yourself to avoid automatic upscaling.
• Above maximum: If your images exceed 6,144 patches, resize them yourself to maintain control over quality.

Recommendations:

1. Resize to multiples of 32: When resizing, aim for dimensions divisible by 32 (e.g., 1280×720, 1024×1024, 1920×1088) to avoid additional processing overhead.
2. Maintain aspect ratio: Preserve original proportions to avoid distortion.
3. Faster uploads: Pre-resized images reduce bandwidth usage.