YBR_FULL_422/YBR_PARTIAL_422 - Samples per pixel - DICOM

This is a discussion on YBR_FULL_422/YBR_PARTIAL_422 - Samples per pixel - DICOM ; I hope samples per pixel for YBR_FULL image would be 3. What would be the samples per pixel for an uncompressed YBR_FULL_422/ YBR_PARTIAL_422. Is it two or three?...

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Thread: YBR_FULL_422/YBR_PARTIAL_422 - Samples per pixel

  1. YBR_FULL_422/YBR_PARTIAL_422 - Samples per pixel

    I hope samples per pixel for YBR_FULL image would be 3.
    What would be the samples per pixel for an uncompressed YBR_FULL_422/
    YBR_PARTIAL_422.
    Is it two or three?


  2. Re: YBR_FULL_422/YBR_PARTIAL_422 - Samples per pixel

    On Feb 22, 8:50 am, "Shafiq" wrote:
    > I hope samples per pixel for YBR_FULL image would be 3.
    > What would be the samples per pixel for an uncompressed YBR_FULL_422/
    > YBR_PARTIAL_422.
    > Is it two or three?


    Text from the DICOM Standard Part 3 describing the YBR_* photometric
    interpretation values is pasted below. The bottomline: YBR_FULL,
    YBR_FULL_422, and YBR_PARTIAL_422 are all 3 samples per pixel, but the
    latter two have employed a physical encoding where 4 values are
    supplied for each pair of adjacent pixels: the two Y values for the
    two pixels followed by a single CB and a single CR value. The CR and
    CB values supply these pixel components for both pixels in a single
    value --ie a sort of simple compression scheme. So even though only 4
    physical data values are supplied for two pixels (giving the
    impression of 2 components per pixel), logically they are still
    providing 3 components per pixel. The six component values (Y1, CR,
    CB), (Y2, CR, CB) are combined to form the two pixel values

    YBR_FULL = Pixel data represent a color image described by one
    luminance (Y) and two chrominance planes (CB and CR). This photometric
    interpretation may be used only when Samples per Pixel (0028,0002) has
    a value of 3. Black is represented by Y equal to zero. The absence of
    color is represented by both CB and CR values equal to half full
    scale. Note:In the case where the Bits Allocated (0028,0100) has value
    of 8 half full scale is 128.

    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. This Photometric
    Interpretation is only allowed with Planar Configuration (0028,0006)
    equal to 0. 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 is often referred to as cosited sampling.

    YBR_PARTIAL_422 = The same as YBR_FULL_422 except that:
    1. black corresponds to Y = 16;
    2. Y is restricted to 220 levels (i.e. the maximum value is 235);
    3. CB and CR each has a minimum value of 16;
    4. CB and CR are restricted to 225 levels (i.e. the maximum value is
    240);
    5. lack of color is represented by CB and CR equal to 128.


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