Function maybeResizeAndDownsampleImageBuffer

src/utils/imageResizer.ts:169–433

(
  imageBuffer: Buffer,
  originalSize: number,
  ext: string,
)

 * Resizes image buffer to meet size and dimension constraints
 */
export async function maybeResizeAndDownsampleImageBuffer(
  imageBuffer: Buffer,
  originalSize: number,
  ext: string,
): Promise<ResizeResult> {
  if (imageBuffer.length === 0) {
    // Empty buffer would fall through the catch block below (sharp throws
    // "Unable to determine image format"), and the fallback's size check
    // `0 ≤ 5MB` would pass it through, yielding an empty base64 string
    // that the API rejects with `image cannot be empty`.
    throw new ImageResizeError('Image file is empty (0 bytes)')
  }
  try {
    const sharp = await getImageProcessor()
    const image = sharp(imageBuffer)
    const metadata = await image.metadata()

    const mediaType = metadata.format ?? ext
    // Normalize "jpg" to "jpeg" for media type compatibility
    const normalizedMediaType = mediaType === 'jpg' ? 'jpeg' : mediaType

    // If dimensions aren't available from metadata
    if (!metadata.width || !metadata.height) {
      if (originalSize > IMAGE_TARGET_RAW_SIZE) {
        // Create fresh sharp instance for compression
        const compressedBuffer = await sharp(imageBuffer)
          .jpeg({ quality: 80 })
          .toBuffer()
        return { buffer: compressedBuffer, mediaType: 'jpeg' }
      }
      // Return without dimensions if we can't determine them
      return { buffer: imageBuffer, mediaType: normalizedMediaType }
    }

    // Store original dimensions (guaranteed to be defined here)
    const originalWidth = metadata.width
    const originalHeight = metadata.height

    // Calculate dimensions while maintaining aspect ratio
    let width = originalWidth
    let height = originalHeight

    // Check if the original file just works
    if (
      originalSize <= IMAGE_TARGET_RAW_SIZE &&
      width <= IMAGE_MAX_WIDTH &&
      height <= IMAGE_MAX_HEIGHT
    ) {
      return {
        buffer: imageBuffer,
        mediaType: normalizedMediaType,
        dimensions: {
          originalWidth,
          originalHeight,
          displayWidth: width,
          displayHeight: height,
        },
      }