Function decodeJpegRegion

Decode a JPEG ROI through the bounded fallback path.

imageio.tiff.TiffDecodeResult decodeJpegRegion(
  scope const(ubyte)[] encoded,
  ulong x,
  ulong y,
  ulong width,
  ulong height
) @safe;

The current baseline codec decodes complete component planes, then crops the requested reference-grid window. region.originX/Y identify the requested source window and each plane origin identifies the corresponding source-plane coordinate. This is intentionally observable full-decode behaviour; native MCU skipping is a later JPEG gate qualification.