Материал: part03

colordesignatedfirstinthePhotometricInterpretationnamecomprisingthemostsignificantbitsoftheCompositePixelCode,followed​ in order by the samples representing the next vector colors, with the sample representing the vector color designated last in the​ Photometric Interpretation name comprising the least significant bits of the Composite Pixel Code. For example, for Photometric In-​ terpretation = "RGB", the most significant "Bits Allocated" bits contain the Red sample, the next "Bits Allocated" bits contain the Green​ sample, and the least significant "Bits Allocated" bits contain the Blue sample.​

C.7.6.3.1.2 Photometric Interpretation​

The value of Photometric Interpretation (0028,0004) specifies the intended interpretation of the image pixel data.​

See PS3.5 for additional restrictions imposed by compressed Transfer Syntaxes.​

See Section 8.2.13 in PS3.5 for constraints that apply when using DICOM Real-Time Video.​

The following values are defined. Other values are permitted if supported by the Transfer Syntax but the meaning is not defined by​ this Standard.​

Defined Terms:​

MONOCHROME1​ Pixeldatarepresentasinglemonochromeimageplane.Theminimumsamplevalueisintendedtobedisplayed​ as white after any VOI gray scale transformations have been performed. See PS3.4. This value may be used​ only when Samples per Pixel (0028,0002) has a value of 1. May be used for pixel data in a Native (uncom-​ pressed) or Encapsulated (compressed) format; see Section 8.2 in PS3.5.​

MONOCHROME2​ Pixeldatarepresentasinglemonochromeimageplane.Theminimumsamplevalueisintendedtobedisplayed​ as black after any VOI gray scale transformations have been performed. See PS3.4. This value may be used​ only when Samples per Pixel (0028,0002) has a value of 1. May be used for pixel data in a Native (uncom-​ pressed) or Encapsulated (compressed) format; see Section 8.2 in PS3.5.​

PALETTE COLOR​ Pixel data describe a color image with a single sample per pixel (single image plane). The pixel value is used​ asanindexintoeachoftheRed,Blue,andGreenPaletteColorLookupTables(0028,1101-1103&1201-1203).​ This value may be used only when Samples per Pixel (0028,0002) has a value of 1. May be used for pixel data​ in a Native (uncompressed) or Encapsulated (compressed) format; see Section 8.2 in PS3.5. When the Pho-​ tometric Interpretation is Palette Color; Red, Blue, and Green Palette Color Lookup Tables shall be present.​

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In the case where Bits Allocated (0028,0100) has a value of 8 then the following equations convert between​ RGB and YCBCR Photometric Interpretation.​

Y = + .2990R + .5870G + .1140B​

CB= - .1687R - .3313G + .5000B + 128​

CR= + .5000R - .4187G - .0813B + 128​

Note​

The above is based on CCIR Recommendation 601-2 dated 1990.​

YBR_FULL_422​ The same as YBR_FULL except that the CB and CR values are sampled horizontally at half the Y rate and as​ a result there are half as many CB and CR values as Y values.​

Planar Configuration (0028,0006) shall be 0. May be used for pixel data in a Native (uncompressed) or Encap-​ sulated (compressed) format; see Section 8.2 in PS3.5.​

Note​

1.​This Photometric Interpretation is primarily used with JPEG compressed bit streams, but is also​ occasionally used for pixel data in a Native (uncompressed) format.​

2.​Though the chrominance channels are downsampled, there are still nominally three channels,​ hence Samples per Pixel (0028,0002) has a value of 3, not 2. I.e., for pixel data in a Native (un-​ compressed) format, the Value Length of Pixel Data (7FE0,0010) is not:​

Rows (0028,0010) * Columns (0028,0011) * Number of Frames (0028,0008) * Samples per Pixel​

(0028,0002) * ( (Bits Allocated (0028,0100)-1)/8 +1)​

padded to an even length, as it would otherwise be, but rather is:​

Rows(0028,0010)*Columns(0028,0011)*NumberofFrames(0028,0008)*2*( (BitsAllocated​ (0028,0100)-1)/8 +1)​

padded to an even length.​

3.​When used to describe JPEG compressed bit streams, the chrominance sub-sampling in the​ JPEG bit stream may differ from this description. E.g., though many JPEG codecs produce only​ horizontally sub-sampled chrominance components (4:2:2), some sub-sample vertically as well​ (4:2:0). Though inaccurate, the use of YBR_FULL_422 to describe both has proven harmless.​ For a discussion of the sub-sampling notation, see [Poynton 2008].​

Two Y values shall be stored followed by one CB and one CR value. The CB and CR values shall be sampled​ at the location of the first of the two Y values. For each Row of Pixels, the first CB and CR samples shall be​ at the location of the first Y sample. The next CB and CR samples shall be at the location of the third Y sample​ etc.​

Note​

This subsampling sited on the even luminance pixels is often referred to as cosited sampling. The​ cositing applies when describing pixel data in a Native (uncompressed) form. When used to describe​ compressed bit streams, the siting depends on the compression scheme. E.g., for JPEG according​ to JFIF [ISO/IEC 10918-5], the siting is midway between luminance samples, whereas for MPEG2​ [ISO/IEC 13818-2], the sampling is cosited with the even luminance pixels. See also [Poynton 2008].​

YBR_PARTIAL_422​Retired. See PS3.3 2017b.​

YBR_PARTIAL_420​Pixel data represent a color image described by one luminance (Y) and two chrominance planes (CB and CR).​

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ThisphotometricinterpretationmaybeusedonlywhenSamplesperPixel(0028,0002)hasavalueof3.Planar​ Configuration(0028,0006)shallbe0.ShallonlybeusedforpixeldatainanEncapsulated(compressed)format;​ see Section 8.2 in PS3.5.​

Note​

This Photometric Interpretation is primarily used with JPEG 2000 compressed bit streams.​

Black is represented by Y equal to zero. The absence of color is represented by both CB and CR values equal​ to zero.​

Regardless of the value of Bits Allocated (0028,0100), the following equations convert between RGB and​ YBR_RCT Photometric Interpretation.​

Y = (R + 2G +B) / 4 (Note: … mean floor)​

CB= B - G​

CR= R - G​

The following equations convert between YBR_RCT and RGB Photometric Interpretation.​

G = Y - (CR+ CB) / 4 ​

R = CR+ G​

B = CB+ G​

Note​

1.​The above is based on [ISO/IEC 15444-1] (JPEG 2000).​

2.​InaJPEG2000bitstream,DClevelshifting(usediftheuntransformedcomponentsareunsigned)​ is applied before forward color transformation, and the transformed components may be signed​ (unlike in JPEG ISO/IEC 10918-1).​

3.​This photometric interpretation is a reversible approximation to the YUV transformation used in​ PAL and SECAM.​

C.7.6.3.1.3 Planar Configuration​

Planar Configuration (0028,0006) indicates whether the color pixel data are encoded color-by-plane or color-by-pixel. This Attribute​ shall be present if Samples per Pixel (0028,0002) has a value greater than 1. It shall not be present otherwise.​

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Enumerated Values:​

0​The sample values for the first pixel are followed by the sample values for the second pixel, etc. For RGB images, this means the​ order of the pixel values encoded shall be R1, G1, B1, R2, G2, B2, …, etc.​

1​Each color plane shall be encoded contiguously. For RGB images, this means the order of the pixel values encoded is R1, R2,​ R3, …, G1, G2, G3, …, B1, B2, B3, etc.​

Note​

PlanarConfiguration(0028,0006)isnotmeaningfulwhenacompressionTransferSyntaxisusedthatinvolvesreorganization​ of sample components in the compressed bit stream. In such cases, since the Attribute is required to be present, then an​ appropriate value to use may be specified in the description of the Transfer Syntax in PS3.5, though in all likelihood the​ value of the Attribute will be ignored by the receiving implementation.​

C.7.6.3.1.4 Pixel Data​

Pixel Data (7FE0,0010) for this image. The order of pixels encoded for each image plane is left to right, top to bottom, i.e., the upper​ left pixel (labeled 1,1) is encoded first followed by the remainder of row 1, followed by the first pixel of row 2 (labeled 2,1) then the​ remainder of row 2 and so on.​

For multi-plane images see Planar Configuration (0028,0006) in this Section.​

C.7.6.3.1.5 Palette Color Lookup Table Descriptor​

The three values of Palette Color Lookup Table Descriptor (0028,1101-1104) describe the format of the Lookup Table Data in the​ corresponding Data Element (0028,1201-1204) or (0028,1221-1223). In this section, the term "input value" is either the Palette Color​ Lookup Table input value described in the Enhanced Palette Color Lookup Table Sequence (0028,140B) or if that Attribute is absent,​ the stored pixel value.​

The first Palette Color Lookup Table Descriptor value is the number of entries in the lookup table. When the number of table entries​ is equal to 216 then this value shall be 0. The first value shall be identical for each of the Red, Green, Blue and Alpha Palette Color​ Lookup Table Descriptors.​

The second Palette Color Lookup Table Descriptor value is the first input value mapped. This input value is mapped to the first entry​ in the Lookup Table Data. All input values less than the first value mapped are also mapped to the first entry in the Lookup Table​ Data if the Photometric Interpretation is PALETTE COLOR.​

Note​

InthecaseoftheSupplementalPaletteColorLUT,thestoredpixelvalueslessthantheseconddescriptorvaluearegrayscale​ values.​

An input value one greater than the first value mapped is mapped to the second entry in the Lookup Table Data. Subsequent input​ values are mapped to the subsequent entries in the Lookup Table Data up to an input value equal to number of entries + first value​ mapped - 1, which is mapped to the last entry in the Lookup Table Data. Input values greater than or equal to number of entries +​ first value mapped are also mapped to the last entry in the Lookup Table Data. The second value shall be identical for each of the​ Red, Green, Blue and Alpha Palette Color Lookup Table Descriptors.​

The third Palette Color Lookup Table Descriptor value specifies the number of bits for each entry in the Lookup Table Data. It shall​ take the value of 8 or 16. The LUT Data shall be stored in a format equivalent to 8 bits allocated when the number of bits for each​ entry is 8, and 16 bits allocated when the number of bits for each entry is 16, where in both cases the high bit is equal to bits allocated-​ 1. The third value shall be identical for each of the Red, Green and Blue Palette Color Lookup Table Descriptors.​

Note​

Some implementations have encoded 8 bit entries with 16 bits allocated, padding the high bits; this can be detected by​ comparing the number of entries specified in the LUT Descriptor with the actual value length of the LUT Data entry. The​ value length in bytes should equal the number of entries if bits allocated is 8, and be twice as long if bits allocated is 16.​

When the Red, Green, or Blue Palette Color Lookup Table Descriptor (0028,1101-1103) are used as part of the Palette Color Lookup​ Table Module or the Supplemental Palette Color Lookup Table Module in an Image or Presentation State IOD, the third value shall​ be equal to 16. When the Alpha Palette Color Lookup Table Descriptor (0028,1104) is used, the third value shall be equal to 8.​

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