Function compressImageBuffer

src/utils/imageResizer.ts:498–577

(
  imageBuffer: Buffer,
  maxBytes: number = IMAGE_TARGET_RAW_SIZE,
  originalMediaType?: string,
)

 * This ensures images fit within context windows while maintaining format when possible.
 */
export async function compressImageBuffer(
  imageBuffer: Buffer,
  maxBytes: number = IMAGE_TARGET_RAW_SIZE,
  originalMediaType?: string,
): Promise<CompressedImageResult> {
  // Extract format from originalMediaType if provided (e.g., "image/png" -> "png")
  const fallbackFormat = originalMediaType?.split('/')[1] || 'jpeg'
  const normalizedFallback = fallbackFormat === 'jpg' ? 'jpeg' : fallbackFormat

  try {
    const sharp = await getImageProcessor()
    const metadata = await sharp(imageBuffer).metadata()
    const format = metadata.format || normalizedFallback
    const originalSize = imageBuffer.length

    const context: ImageCompressionContext = {
      imageBuffer,
      metadata,
      format,
      maxBytes,
      originalSize,
    }

    // If image is already within size limit, return as-is without processing
    if (originalSize <= maxBytes) {
      return createCompressedImageResult(imageBuffer, format, originalSize)
    }

    // Try progressive resizing with format preservation
    const resizedResult = await tryProgressiveResizing(context, sharp)
    if (resizedResult) {
      return resizedResult
    }

    // For PNG, try palette optimization
    if (format === 'png') {
      const palettizedResult = await tryPalettePNG(context, sharp)
      if (palettizedResult) {
        return palettizedResult
      }
    }

    // Try JPEG conversion with moderate compression
    const jpegResult = await tryJPEGConversion(context, 50, sharp)
    if (jpegResult) {
      return jpegResult
    }

    // Last resort: ultra-compressed JPEG
    return await createUltraCompressedJPEG(context, sharp)
  } catch (error) {
    // Log the error and emit analytics event
    logError(error as Error)
    const errorType = classifyImageError(error)
    const errorMsg = errorMessage(error)
    logEvent('tengu_image_compress_failed', {
      original_size_bytes: imageBuffer.length,
      max_bytes: maxBytes,