JBP Block Codec

Version: 1.0
URI: https://awslabs.github.io/osml-imagery-io/codecs/jbp-block
Codec type: array-to-bytes

Decodes uncompressed JBP/NITF/NSIF image blocks into NumPy arrays. Performs interleave conversion (from the source IMODE to band-sequential) and big-endian to native-endian byte swap.

This codec is NITF-specific — it uses NITF interleave modes (IMODE) and pixel value types (PVTYPE) to interpret the raw pixel bytes.

Document Conventions

The key words “MUST”, “MUST NOT”, “SHOULD”, and “MAY” in this document are to be interpreted as described in RFC 2119.

Codec Identifier

The value of the name member in the codec metadata MUST be https://awslabs.github.io/osml-imagery-io/codecs/jbp-block.

Encoded Representation

The encoded representation MUST be raw uncompressed pixel data as defined by MIL-STD-2500C for NITF image data segments. The byte sequence contains pixel values in big-endian byte order arranged according to the interleave mode specified in the imode configuration parameter.

The total byte length MUST equal num_bands * block_height * block_width * (nbpp / 8).

Configuration Parameters

Field	Type	Required	Description
num_bands	int	Yes	Number of bands.
block_height	int	Yes	Block height in pixels.
block_width	int	Yes	Block width in pixels.
nbpp	int	Yes	Bits per pixel per band (8, 16, 32, or 64).
imode	string	Yes	NITF interleave mode: "B" (band interleaved by block), "P" (pixel interleaved), "R" (row interleaved), or "S" (band sequential).
pvtype	string	Yes	NITF pixel value type: "INT" (unsigned integer), "SI" (signed integer), "R" (real/float), or "C" (complex).

PVTYPE / NBPP to NumPy dtype Mapping

PVTYPE	NBPP	NumPy dtype
INT	8	uint8
INT	16	uint16
INT	32	uint32
SI	8	int8
SI	16	int16
SI	32	int32
R	32	float32
R	64	float64

Algorithm

Decoding

1. Validate that the input data length equals num_bands * block_height * block_width * (nbpp / 8) bytes.

2. Convert the pixel data from the input imode to band-sequential (BSQ) format.

3. Swap big-endian bytes to native-endian byte order.

4. Return an array with shape (num_bands, block_height, block_width) and the dtype corresponding to the pvtype/nbpp combination.

Encoding

Encoding is not currently specified. See Implementation Notes.

Example Configuration

{
    "name": "https://awslabs.github.io/osml-imagery-io/codecs/jbp-block",
    "configuration": {
        "num_bands": 3,
        "block_height": 256,
        "block_width": 256,
        "nbpp": 16,
        "imode": "P",
        "pvtype": "INT"
    }
}

References

• MIL-STD-2500C — National Imagery Transmission Format (NITF)

• RFC 2119 — Key words for use in RFCs to Indicate Requirement Levels

Implementation Notes

aws.osml.io.zarr_codecs.JbpBlockCodec — see API Reference.

Only the decode path is implemented. Calling encode() raises NotImplementedError.