Материал: part05

Example 1: Pixel and Overlay Data Cells

Pixel Sample 1

Bits Allocated = 16

Bits Stored = 12

High Bit = 11

Figure D.2-1. Example 1 of Pixel and Overlay Data Cells​

Figure D.2-2 Example 2 of Pixel and Overlay Data Cells has been retired. See PS3.3 2014c.​

Example 3: Pixel and Overlay Data Cells

Bits Allocated = 8

Bits Stored = 6

High Bit = 5

Figure D.2-3. Example 3 of Pixel and Overlay Data Cells​

Example 4: Overlay Data Cells

15 14131211 10 9 8 7 6 5 4 3 2 1 0

Bits Allocated = 1

Bits Position = 0

Figure D.2-4. Example 4 of Overlay Data Cells​

Note​

In this example, the Overlay Bits are numbered in the same manner that Pixel Cells are numbered in the other examples in​ this Annex. That is Overlay Bit 1 is the first bit of the Overlay Plane, encoded from left to right and top to bottom, a row at a​ time.​

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Example 5: Single Bit (Binary) Pixel Data Cells

15 14131211 10 9 8 7 6 5 4 3 2 1 0

Bits Allocated = 1

Bits Stored = 1

High Bit = 0

Figure D.2-5. Example 5 of Single Bit Pixel Data Cells (VR=OW)​

D.3 Examples of Float and Double Float Pixel Data​

Float Pixel Data having the Value Representation OF always has 32 bits allocated; the resulting byte streams pictured in Figure D.3-​ 1 are as they would be transmitted across a network and/or stored on media.​

Float Pixel Data Byte Stream (VR = OF); 32 bits allocated)

Little Endian Transfer Syntax

Figure D.3-1. Sample Float Pixel Data Byte Streams for VR = OF​

Double Float Pixel Data having the Value Representation OD always has 64 bits allocated; the resulting byte streams pictured in​ Figure D.3-2 are as they would be transmitted across a network and/or stored on media.​

Double Pixel Data Byte Stream (VR = OD; 64 bits allocated)

Little Endian Transfer Syntax

Figure D.3-2. Sample Float Pixel Data Byte Streams for VR = OD​

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E DICOM Default Character Repertoire​ (Normative)​

The default repertoire for character strings in DICOM is the Basic G0 Set of the International Reference Version of ISO 646:1990​ (ISO IR-6). In addition, the Control Characters LF, FF, CR, TAB and ESC are supported. These control characters are a subset of​ the C0 set defined in ISO 646:1990 and ISO 6429:1990.​

The byte encoding of the Default Character Repertoire is pictured in Table E-1. This table can be used to derive both ISO column/row​ byte values and hex values for encoded representations (see Section 6.1.1).​

Table E-1. DICOM Default Character Repertoire Encoding​

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F Encapsulated Images As Part of A DICOM​

Message (Informative)​

The following remarks apply generally to communicating an encoded image within a message structure according to the DICOM​ Standard:​

a)In the course of including an encoded image in a DICOM message, the encoding is not changed. The encoded data stream is​ merely segmented and encapsulated according to the protocols of the DICOM Standard. After unpacking the DICOM message, the​ encoded data stream can be fully reconstructed at the receiving node.​

b)TheobjectdefinitionoftheDICOMStandardisalwaysdeterminingformatandotherchoicesthataspecificencodingimplementation​ may offer. The encoded image must be consistent with the definition of the object of which the encoded image is part. For example:​

1)If the object is defined to contain 10-bit pixel data, it is assumed that the encoding process is one that accepts at least 10-bit data.​ Hence, there is no need for defining separate Transfer Syntaxes, e.g., for 8-bit or 12-bit implementations. Any 12-bit implementation​ is assumed to operate in an 8-bit process if the object is defined to contain 8-bit data.​

2)If the image of an object is interleaved, the encoding process must reproduce the interleaving.​

c)Specifications in the encoding file header must be consistent with the DICOM Message header, e.g., regarding the number of rows​ and columns.​

d)The byte order specification of an encoded file is not altered in the course of encapsulating it in a DICOM message.​

F.1 Encapsulated JPEG Encoded Images​

The International Standards Organization (ISO/IEC JTC1/SC2/WG10) has prepared an International Standard, ISO 10918-1 (JPEG​ Part 1) and International Draft Standard ISO 10918-2 (JPEG Part 2), for the digital compression and coding of continuous-tone still​ images. This standard is collectively known as the JPEG Standard.​

Part 1 of the JPEG Standard sets out requirements and implementation guidelines for the coded representation of compressed image​ data to be interchanged between applications. The processes and representations are intended to be generic in order to support the​ broadrangeofapplicationsforcolorandgrayscalestillimagesforthepurposeofcommunicationsandstoragewithincomputersystems.​ Part 2 of the JPEG Standard defines tests for determining whether implementations comply with the requirements of the various en-​ coding and decoding processes specified in Part 1 of the JPEG Standard.​

The JPEG Standard specifies lossy and lossless code processes. The lossy coding is based on the discrete cosine transform (DCT),​ permitting data compression with an adjustable compression ratio. The lossless coding employs differential pulse code modulation​ (DPCM).​

The JPEG Standard permits a variety of coding processes for the coder and decoder. These processes differ in coding schemes for​ the quantified data and in sample precision. The coding processes are consecutively numbered as defined in the International Draft​ Standard ISO 10918-2 (JPEG Part 2), and are summarized in Table F.1-1. The simplest DCT-based coding process is referred to as​ Baseline Sequential with Huffman Coding for 8-bit Samples.​

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