pi-agent-integrated/pi-web/lib/image-attachments.ts

export const MAX_ATTACHED_IMAGE_BYTES = 10 * 1024 * 1024;
export const MAX_ATTACHED_IMAGES = 10;

/** 上传时自动压缩：长边超过此像素的 JPEG 缩到此边长（相机照片主场景，视觉模型输入上限 ~1344px，1600 无损）。 */
export const MAX_IMAGE_EDGE_PX = 1600;
/** JPEG 重编码质量：避免伪影糊掉边缘/小字。 */
export const IMAGE_JPEG_QUALITY = 0.85;

export interface Base64ImageAttachment {
  data: string;
  mimeType: string;
}

function isBase64DataChar(code: number): boolean {
  return (code >= 0x41 && code <= 0x5a)
    || (code >= 0x61 && code <= 0x7a)
    || (code >= 0x30 && code <= 0x39)
    || code === 0x2b
    || code === 0x2f;
}

export function getBase64DecodedByteLength(data: string): number | null {
  if (!data || data.length % 4 !== 0) return null;
  const padding = data.endsWith("==") ? 2 : data.endsWith("=") ? 1 : 0;
  const dataEnd = data.length - padding;
  for (let index = 0; index < dataEnd; index += 1) {
    if (!isBase64DataChar(data.charCodeAt(index))) return null;
  }
  for (let index = dataEnd; index < data.length; index += 1) {
    if (data[index] !== "=") return null;
  }
  return (data.length / 4) * 3 - padding;
}

export function isBase64ImageWithinLimits(value: unknown): value is Base64ImageAttachment {
  if (!value || typeof value !== "object") return false;
  const image = value as Partial<Base64ImageAttachment>;
  if (typeof image.data !== "string" || typeof image.mimeType !== "string" || !image.mimeType.startsWith("image/")) {
    return false;
  }
  const bytes = getBase64DecodedByteLength(image.data);
  return bytes !== null && bytes <= MAX_ATTACHED_IMAGE_BYTES;
}

/**
 * 上传前压缩：仅 JPEG 且长边超过 MAX_IMAGE_EDGE_PX 时缩放重编码（EXIF 方向由
 * createImageBitmap 默认 from-image 纠正）。PNG/WebP/GIF 原样返回（无损/动画场景）。
 * 重编码无收益（更小或失败）时退回原文件。
 */
export async function compressImageFile(file: File): Promise<File> {
  if (file.type !== "image/jpeg") return file;
  let bitmap: ImageBitmap;
  try {
    bitmap = await createImageBitmap(file);
  } catch {
    return file; // 解码失败退化为原文件
  }
  try {
    const edge = Math.max(bitmap.width, bitmap.height);
    if (edge <= MAX_IMAGE_EDGE_PX) return file; // 本就不大，避免无谓重编码
    const scale = MAX_IMAGE_EDGE_PX / edge;
    const width = Math.max(1, Math.round(bitmap.width * scale));
    const height = Math.max(1, Math.round(bitmap.height * scale));
    const canvas = document.createElement("canvas");
    canvas.width = width;
    canvas.height = height;
    const ctx = canvas.getContext("2d");
    if (!ctx) return file;
    ctx.drawImage(bitmap, 0, 0, width, height);
    const blob = await new Promise<Blob | null>((resolve) =>
      canvas.toBlob(resolve, "image/jpeg", IMAGE_JPEG_QUALITY)
    );
    if (!blob || blob.size >= file.size) return file; // 重编码无收益则用原文件
    return new File([blob], file.name.replace(/\.\w+$/, ".jpg"), { type: "image/jpeg" });
  } finally {
    bitmap.close();
  }
}

/** Return an API-safe error for prompt, steering, and follow-up image arrays. */
export function validateAgentImages(value: unknown): string | null {
  if (value === undefined) return null;
  if (!Array.isArray(value)) return "images must be an array";
  if (value.length > MAX_ATTACHED_IMAGES) {
    return `A message can include at most ${MAX_ATTACHED_IMAGES} images`;
  }
  for (const image of value) {
    if (!image || typeof image !== "object" || (image as { type?: unknown }).type !== "image") {
      return "Each attachment must be an image";
    }
    if (!isBase64ImageWithinLimits(image)) {
      return `Each image must be valid base64 image data of ${MAX_ATTACHED_IMAGE_BYTES / (1024 * 1024)}MB or smaller`;
    }
  }
  return null;
}