8-bit grayscale, 1 byte per pixel. No transparency.
Embed encoded JPEG bytes directly via /DCTDecode (no re-encode). width/height must match the JPEG's own dimensions. Set grayscale for a single-component (DeviceGray) JPEG.
/DCTDecode
8-bit RGB, 3 bytes per pixel (R,G,B). No transparency.
8-bit RGBA, 4 bytes per pixel (R,G,B,A). The alpha channel becomes a /SMask; if every pixel is fully opaque the mask is omitted.
/SMask