ISO/IEC 18477-3:2023 情報技術 | ページ 6

3.1.1

ASCII encoding

encoding of text characters and text strings according to ISO/IEC 10646-1

3.1.2

base decoding path

process of decoding legacy codestream and refinement data to the base image, jointly with all further steps, until residual data is added to the values obtained from the residual codestream

3.1.3

base image

collection of sample values obtained by entropy, decoding the discrete cosine transformation (DCT) coefficients of the legacy codestream and the refinement codestream, and inversely DCT transforming them jointly

3.1.4

bit stream

partially encoded or decoded sequence of bits comprising an entropy-coded segment

3.1.5

box

structured collection of data describing the image or the image-decoding process embedded into one or multiple APP₁₁ marker segments

Note 1 to entry: See Annex A for the definition of boxes.

3.1.6

byte

group of 8 bits

3.1.7

compression

reduction in the number of bits used to represent source image data

3.1.8

component

two-dimensional array of samples having the same designation in the output or display device

Note 1 to entry: An image typically consists of several components, e.g. red, green and blue.

3.1.9

continuous-tone image

image whose components have more than one bit per sample

3.1.10

decoder

embodiment of a decoding process

3.1.11

decoding process

process which takes as its input compressed image data and outputs a continuous-tone image

3.1.12

encoder

embodiment of an encoding process

3.1.13

encoding process

process which takes as its input a continuous-tone image and outputs compressed image data

3.1.14

extension image

sample values as reconstructed by inverse quantization and inverse discrete cosine transformation (DCT) applied to the entropy-decoded coefficients described by the refinement scan, residual scan and residual refinement scans

3.1.15

high-dynamic range

HDR

image or image data comprised of more than 8 bits per sample

3.1.16

legacy codestream

collection of markers and syntax elements defined by Rec. ITU-T T.81 | ISO/IEC 10918-1 without any syntax elements defined by ISO/IEC 18477-1, ISO/IEC 18477-2, ISO/IEC 18477-3

Note 1 to entry: In this definition, the legacy codestream consists of the collection of all markers except those APP₁₁ markers that describe JPEG XT boxes by the syntax defined in Annex A.

3.1.17

legacy decoder

embodiment of a decoding process conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1, confined to the lossy discrete cosine transformation (DCT) process and the baseline, sequential or progressive modes, decoding at most four components to 8 bits per component

3.1.18

lossless

encoding and decoding processes and procedures in which the output of the decoding procedure(s) is identical to the input to the encoding procedure(s)

3.1.19

lossy

encoding and decoding processes which are not lossless

3.1.20

low-dynamic range

LDR

image or image data comprised of data with no more than 8 bits per sample

3.1.21

marker

2-byte code in which the first byte is hexadecimal FF and the second byte is a value between 1 and hexadecimal FE

3.1.22

marker segment

marker together with its associated set of parameters

3.1.23

pixel

collection of sample values in the spatial image domain having all the same sample coordinates

Note 1 to entry: A pixel may consist of three samples describing its red, green and blue value.

3.1.24

point transformation

scaling of a sample or discrete cosine transformation (DCT) coefficient by a factor

3.1.25

precision

number of bits allocated to a particular sample or discrete cosine transformation (DCT) coefficient

3.1.26

procedure

set of steps which accomplishes one of the tasks which comprises an encoding or decoding process

3.1.27

residual decoding path

collection of operations applied to the entropy coded data contained in the residual data box and residual refinement scan boxes up to the point where this data is merged with the base image to form the final output image

3.1.28

residual image

sample values as reconstructed by inverse quantization and inverse discrete cosine transformation (DCT) applied to the entropy-decoded coefficients described by the residual scan and residual refinement scans

3.1.29

refinement scan

additional pass over the image data that is invisible to legacy decoders, which provides additional least significant bits to extend the precision of the discrete cosine transformation (DCT) transformed coefficients

Note 1 to entry: Refinement scans can be either applied in the base or residual decoding path.

3.1.30

sample

one element in the two-dimensional image array which comprises a component

3.1.31

sample grid

common coordinate system for all samples of an image such that the samples at the top left edge of the image have the coordinates (0, 0), the first coordinate increases towards the right, the second towards the bottom

3.1.32

superbox

box that carries other boxes as payload data

3.1.33

zero byte

0x00 byte