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.