anthropicImageTokens (anthropic-vision)

Computes Anthropic vision token usage for an image with given dimensions and tier, resizing via binary search to respect long-edge and token caps.

export function anthropicImageTokens(width: number, height: number, tier: AnthropicVisionTier): number {
  const { longEdgeMax, tokenCap } = ANTHROPIC_TIER_CAPS[tier];
  if (Math.max(width, height) <= longEdgeMax && patchTokens(width, height) <= tokenCap) {
    return patchTokens(width, height);
  }
  const long = Math.max(width, height);
  const short = Math.min(width, height);
  const tokensAt = (edge: number): number => patchTokens(edge, Math.round((short * edge) / long));
  let lo = PATCH_PX;
  let hi = Math.min(longEdgeMax, long);
  while (lo < hi) {
    const mid = Math.ceil((lo + hi + 1) / 2);
    if (tokensAt(mid) <= tokenCap) lo = mid;
    else hi = mid - 1;
  }
  return tokensAt(lo);
}