+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: SMPTE 170M Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.630
-
- - 0.340
-
- - .. row 3
-
- - Green
-
- - 0.310
-
- - 0.595
-
- - .. row 4
-
- - Blue
-
- - 0.155
-
- - 0.070
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.630
+ - 0.340
+ * - Green
+ - 0.310
+ - 0.595
+ * - Blue
+ - 0.155
+ - 0.070
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
The red, green and blue chromaticities are also often referred to as the
The transfer function defined for SMPTE 170M is the same as the one
defined in Rec. 709.
- L' = -1.099(-L) :sup:`0.45` + 0.099 for L ≤ -0.018
+.. math::
+
+ L' = -1.099(-L)^{0.45} + 0.099 \text{, for } L \le-0.018
- L' = 4.5L for -0.018 < L < 0.018
+ L' = 4.5L \text{, for } -0.018 < L < 0.018
- L' = 1.099L :sup:`0.45` - 0.099 for L ≥ 0.018
+ L' = 1.099L^{0.45} - 0.099 \text{, for } L \ge 0.018
Inverse Transfer function:
- L = -((L' - 0.099) / -1.099) :sup:`1/0.45` for L' ≤ -0.081
+.. math::
- L = L' / 4.5 for -0.081 < L' < 0.081
+ L = -\left( \frac{L' - 0.099}{-1.099} \right) ^{\frac{1}{0.45}} \text{, for } L' \le -0.081
- L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081
+ L = \frac{L'}{4.5} \text{, for } -0.081 < L' < 0.081
+
+ L = \left(\frac{L' + 0.099}{1.099}\right)^{\frac{1}{0.45} } \text{, for } L' \ge 0.081
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_601`` encoding:
- Y' = 0.299R' + 0.587G' + 0.114B'
+.. math::
- Cb = -0.169R' - 0.331G' + 0.5B'
+ Y' = 0.2990R' + 0.5870G' + 0.1140B'
- Cr = 0.5R' - 0.419G' - 0.081B'
+ Cb = -0.1687R' - 0.3313G' + 0.5B'
+
+ Cr = 0.5R' - 0.4187G' - 0.0813B'
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. This conversion to Y'CbCr is identical to the one defined in
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: Rec. 709 Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.640
-
- - 0.330
-
- - .. row 3
-
- - Green
-
- - 0.300
-
- - 0.600
-
- - .. row 4
-
- - Blue
-
- - 0.150
-
- - 0.060
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.640
+ - 0.330
+ * - Green
+ - 0.300
+ - 0.600
+ * - Blue
+ - 0.150
+ - 0.060
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
The full name of this standard is Rec. ITU-R BT.709-5.
Transfer function. Normally L is in the range [0…1], but for the
extended gamut xvYCC encoding values outside that range are allowed.
- L' = -1.099(-L) :sup:`0.45` + 0.099 for L ≤ -0.018
+.. math::
+
+ L' = -1.099(-L)^{0.45} + 0.099 \text{, for } L \le -0.018
- L' = 4.5L for -0.018 < L < 0.018
+ L' = 4.5L \text{, for } -0.018 < L < 0.018
- L' = 1.099L :sup:`0.45` - 0.099 for L ≥ 0.018
+ L' = 1.099L^{0.45} - 0.099 \text{, for } L \ge 0.018
Inverse Transfer function:
- L = -((L' - 0.099) / -1.099) :sup:`1/0.45` for L' ≤ -0.081
+.. math::
- L = L' / 4.5 for -0.081 < L' < 0.081
+ L = -\left( \frac{L' - 0.099}{-1.099} \right)^\frac{1}{0.45} \text{, for } L' \le -0.081
- L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081
+ L = \frac{L'}{4.5}\text{, for } -0.081 < L' < 0.081
+
+ L = \left(\frac{L' + 0.099}{1.099}\right)^{\frac{1}{0.45} } \text{, for } L' \ge 0.081
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_709`` encoding:
+.. math::
+
Y' = 0.2126R' + 0.7152G' + 0.0722B'
Cb = -0.1146R' - 0.3854G' + 0.5B'
that are outside the range [0…1]. The resulting Y', Cb and Cr values are
scaled and offset:
- Y' = (219 / 256) * (0.2126R' + 0.7152G' + 0.0722B') + (16 / 256)
+.. math::
- Cb = (224 / 256) * (-0.1146R' - 0.3854G' + 0.5B')
+ Y' = \frac{219}{256} * (0.2126R' + 0.7152G' + 0.0722B') + \frac{16}{256}
- Cr = (224 / 256) * (0.5R' - 0.4542G' - 0.0458B')
+ Cb = \frac{224}{256} * (-0.1146R' - 0.3854G' + 0.5B')
+
+ Cr = \frac{224}{256} * (0.5R' - 0.4542G' - 0.0458B')
The xvYCC 601 encoding (``V4L2_YCBCR_ENC_XV601``, :ref:`xvycc`) is
similar to the BT.601 encoding, but it allows for R', G' and B' values
that are outside the range [0…1]. The resulting Y', Cb and Cr values are
scaled and offset:
- Y' = (219 / 256) * (0.299R' + 0.587G' + 0.114B') + (16 / 256)
+.. math::
+
+ Y' = \frac{219}{256} * (0.2990R' + 0.5870G' + 0.1140B') + \frac{16}{256}
- Cb = (224 / 256) * (-0.169R' - 0.331G' + 0.5B')
+ Cb = \frac{224}{256} * (-0.1687R' - 0.3313G' + 0.5B')
- Cr = (224 / 256) * (0.5R' - 0.419G' - 0.081B')
+ Cr = \frac{224}{256} * (0.5R' - 0.4187G' - 0.0813B')
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. The non-standard xvYCC 709 or xvYCC 601 encodings can be
The :ref:`srgb` standard defines the colorspace used by most webcams
and computer graphics. The default transfer function is
``V4L2_XFER_FUNC_SRGB``. The default Y'CbCr encoding is
-``V4L2_YCBCR_ENC_SYCC``. The default Y'CbCr quantization is full range.
+``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is full range.
The chromaticities of the primary colors and the white reference are:
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: sRGB Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.640
-
- - 0.330
-
- - .. row 3
-
- - Green
-
- - 0.300
-
- - 0.600
-
- - .. row 4
-
- - Blue
-
- - 0.150
-
- - 0.060
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.640
+ - 0.330
+ * - Green
+ - 0.300
+ - 0.600
+ * - Blue
+ - 0.150
+ - 0.060
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
These chromaticities are identical to the Rec. 709 colorspace.
Transfer function. Note that negative values for L are only used by the
Y'CbCr conversion.
- L' = -1.055(-L) :sup:`1/2.4` + 0.055 for L < -0.0031308
+.. math::
- L' = 12.92L for -0.0031308 ≤ L ≤ 0.0031308
+ L' = -1.055(-L)^{\frac{1}{2.4} } + 0.055\text{, for }L < -0.0031308
- L' = 1.055L :sup:`1/2.4` - 0.055 for 0.0031308 < L ≤ 1
+ L' = 12.92L\text{, for }-0.0031308 \le L \le 0.0031308
+
+ L' = 1.055L ^{\frac{1}{2.4} } - 0.055\text{, for }0.0031308 < L \le 1
Inverse Transfer function:
- L = -((-L' + 0.055) / 1.055) :sup:`2.4` for L' < -0.04045
+.. math::
+
+ L = -((-L' + 0.055) / 1.055) ^{2.4}\text{, for }L' < -0.04045
- L = L' / 12.92 for -0.04045 ≤ L' ≤ 0.04045
+ L = L' / 12.92\text{, for }-0.04045 \le L' \le 0.04045
- L = ((L' + 0.055) / 1.055) :sup:`2.4` for L' > 0.04045
+ L = ((L' + 0.055) / 1.055) ^{2.4}\text{, for }L' > 0.04045
The luminance (Y') and color difference (Cb and Cr) are obtained with
-the following ``V4L2_YCBCR_ENC_SYCC`` encoding as defined by
-:ref:`sycc`:
+the following ``V4L2_YCBCR_ENC_601`` encoding as defined by :ref:`sycc`:
+
+.. math::
Y' = 0.2990R' + 0.5870G' + 0.1140B'
Cr = 0.5R' - 0.4187G' - 0.0813B'
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
-[-0.5…0.5]. The ``V4L2_YCBCR_ENC_SYCC`` quantization is always full
-range. Although this Y'CbCr encoding looks very similar to the
-``V4L2_YCBCR_ENC_XV601`` encoding, it is not. The
-``V4L2_YCBCR_ENC_XV601`` scales and offsets the Y'CbCr values before
-quantization, but this encoding does not do that.
+[-0.5…0.5]. This transform is identical to one defined in SMPTE
+170M/BT.601. The Y'CbCr quantization is full range.
.. _col-adobergb:
graphics that use the AdobeRGB colorspace. This is also known as the
:ref:`oprgb` standard. The default transfer function is
``V4L2_XFER_FUNC_ADOBERGB``. The default Y'CbCr encoding is
-``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is limited
+``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is full
range. The chromaticities of the primary colors and the white reference
are:
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: Adobe RGB Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.6400
-
- - 0.3300
-
- - .. row 3
-
- - Green
-
- - 0.2100
-
- - 0.7100
-
- - .. row 4
-
- - Blue
-
- - 0.1500
-
- - 0.0600
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.6400
+ - 0.3300
+ * - Green
+ - 0.2100
+ - 0.7100
+ * - Blue
+ - 0.1500
+ - 0.0600
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
Transfer function:
- L' = L :sup:`1/2.19921875`
+.. math::
+
+ L' = L ^{\frac{1}{2.19921875}}
Inverse Transfer function:
- L = L' :sup:`2.19921875`
+.. math::
+
+ L = L'^{(2.19921875)}
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_601`` encoding:
- Y' = 0.299R' + 0.587G' + 0.114B'
+.. math::
- Cb = -0.169R' - 0.331G' + 0.5B'
+ Y' = 0.2990R' + 0.5870G' + 0.1140B'
- Cr = 0.5R' - 0.419G' - 0.081B'
+ Cb = -0.1687R' - 0.3313G' + 0.5B'
+
+ Cr = 0.5R' - 0.4187G' - 0.0813B'
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. This transform is identical to one defined in SMPTE
-170M/BT.601. The Y'CbCr quantization is limited range.
+170M/BT.601. The Y'CbCr quantization is full range.
.. _col-bt2020:
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: BT.2020 Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.708
-
- - 0.292
-
- - .. row 3
-
- - Green
-
- - 0.170
-
- - 0.797
-
- - .. row 4
-
- - Blue
-
- - 0.131
-
- - 0.046
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.708
+ - 0.292
+ * - Green
+ - 0.170
+ - 0.797
+ * - Blue
+ - 0.131
+ - 0.046
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
Transfer function (same as Rec. 709):
- L' = 4.5L for 0 ≤ L < 0.018
+.. math::
- L' = 1.099L :sup:`0.45` - 0.099 for 0.018 ≤ L ≤ 1
+ L' = 4.5L\text{, for }0 \le L < 0.018
+
+ L' = 1.099L ^{0.45} - 0.099\text{, for } 0.018 \le L \le 1
Inverse Transfer function:
- L = L' / 4.5 for L' < 0.081
+.. math::
+
+ L = L' / 4.5\text{, for } L' < 0.081
- L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081
+ L = \left( \frac{L' + 0.099}{1.099}\right) ^{\frac{1}{0.45} }\text{, for } L' \ge 0.081
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_BT2020`` encoding:
+.. math::
+
Y' = 0.2627R' + 0.6780G' + 0.0593B'
Cb = -0.1396R' - 0.3604G' + 0.5B'
Luma:
- Yc' = (0.2627R + 0.6780G + 0.0593B)'
-
-B' - Yc' ≤ 0:
-
- Cbc = (B' - Yc') / 1.9404
-
-B' - Yc' > 0:
-
- Cbc = (B' - Yc') / 1.5816
-
-R' - Yc' ≤ 0:
-
- Crc = (R' - Y') / 1.7184
-
-R' - Yc' > 0:
-
- Crc = (R' - Y') / 0.9936
+.. math::
+ :nowrap:
+
+ \begin{align*}
+ Yc' = (0.2627R + 0.6780G + 0.0593B)'& \\
+ B' - Yc' \le 0:& \\
+ &Cbc = (B' - Yc') / 1.9404 \\
+ B' - Yc' > 0: & \\
+ &Cbc = (B' - Yc') / 1.5816 \\
+ R' - Yc' \le 0:& \\
+ &Crc = (R' - Y') / 1.7184 \\
+ R' - Yc' > 0:& \\
+ &Crc = (R' - Y') / 0.9936
+ \end{align*}
Yc' is clamped to the range [0…1] and Cbc and Crc are clamped to the
range [-0.5…0.5]. The Yc'CbcCrc quantization is limited range.
The :ref:`smpte431` standard defines the colorspace used by cinema
projectors that use the DCI-P3 colorspace. The default transfer function
is ``V4L2_XFER_FUNC_DCI_P3``. The default Y'CbCr encoding is
-``V4L2_YCBCR_ENC_709``.
+``V4L2_YCBCR_ENC_709``. The default Y'CbCr quantization is limited range.
+
+.. note::
-.. note:: Note that this colorspace does not specify a
+ Note that this colorspace standard does not specify a
Y'CbCr encoding since it is not meant to be encoded to Y'CbCr. So this
- default Y'CbCr encoding was picked because it is the HDTV encoding. The
- default Y'CbCr quantization is limited range. The chromaticities of the
- primary colors and the white reference are:
+ default Y'CbCr encoding was picked because it is the HDTV encoding.
+
+The chromaticities of the primary colors and the white reference are:
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: DCI-P3 Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.6800
-
- - 0.3200
-
- - .. row 3
-
- - Green
-
- - 0.2650
-
- - 0.6900
-
- - .. row 4
-
- - Blue
-
- - 0.1500
-
- - 0.0600
-
- - .. row 5
-
- - White Reference
-
- - 0.3140
-
- - 0.3510
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.6800
+ - 0.3200
+ * - Green
+ - 0.2650
+ - 0.6900
+ * - Blue
+ - 0.1500
+ - 0.0600
+ * - White Reference
+ - 0.3140
+ - 0.3510
Transfer function:
- L' = L :sup:`1/2.6`
+.. math::
+
+ L' = L^{\frac{1}{2.6}}
Inverse Transfer function:
- L = L' :sup:`2.6`
+.. math::
+
+ L = L'^{(2.6)}
Y'CbCr encoding is not specified. V4L2 defaults to Rec. 709.
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: SMPTE 240M Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.630
-
- - 0.340
-
- - .. row 3
-
- - Green
-
- - 0.310
-
- - 0.595
-
- - .. row 4
-
- - Blue
-
- - 0.155
-
- - 0.070
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.630
+ - 0.340
+ * - Green
+ - 0.310
+ - 0.595
+ * - Blue
+ - 0.155
+ - 0.070
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
These chromaticities are identical to the SMPTE 170M colorspace.
Transfer function:
- L' = 4L for 0 ≤ L < 0.0228
+.. math::
- L' = 1.1115L :sup:`0.45` - 0.1115 for 0.0228 ≤ L ≤ 1
+ L' = 4L\text{, for } 0 \le L < 0.0228
+
+ L' = 1.1115L ^{0.45} - 0.1115\text{, for } 0.0228 \le L \le 1
Inverse Transfer function:
- L = L' / 4 for 0 ≤ L' < 0.0913
+.. math::
+
+ L = \frac{L'}{4}\text{, for } 0 \le L' < 0.0913
- L = ((L' + 0.1115) / 1.1115) :sup:`1/0.45` for L' ≥ 0.0913
+ L = \left( \frac{L' + 0.1115}{1.1115}\right) ^{\frac{1}{0.45} }\text{, for } L' \ge 0.0913
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_SMPTE240M`` encoding:
+.. math::
+
Y' = 0.2122R' + 0.7013G' + 0.0865B'
Cb = -0.1161R' - 0.3839G' + 0.5B'
Cr = 0.5R' - 0.4451G' - 0.0549B'
-Yc' is clamped to the range [0…1] and Cbc and Crc are clamped to the
+Y' is clamped to the range [0…1] and Cb and Cr are clamped to the
range [-0.5…0.5]. The Y'CbCr quantization is limited range.
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: NTSC 1953 Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.67
-
- - 0.33
-
- - .. row 3
-
- - Green
-
- - 0.21
-
- - 0.71
-
- - .. row 4
-
- - Blue
-
- - 0.14
-
- - 0.08
-
- - .. row 5
-
- - White Reference (C)
-
- - 0.310
-
- - 0.316
-
-
-.. note:: This colorspace uses Illuminant C instead of D65 as the white
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.67
+ - 0.33
+ * - Green
+ - 0.21
+ - 0.71
+ * - Blue
+ - 0.14
+ - 0.08
+ * - White Reference (C)
+ - 0.310
+ - 0.316
+
+
+.. note::
+
+ This colorspace uses Illuminant C instead of D65 as the white
reference. To correctly convert an image in this colorspace to another
that uses D65 you need to apply a chromatic adaptation algorithm such as
the Bradford method.
The transfer function was never properly defined for NTSC 1953. The Rec.
709 transfer function is recommended in the literature:
- L' = 4.5L for 0 ≤ L < 0.018
+.. math::
+
+ L' = 4.5L\text{, for } 0 \le L < 0.018
- L' = 1.099L :sup:`0.45` - 0.099 for 0.018 ≤ L ≤ 1
+ L' = 1.099L ^{0.45} - 0.099\text{, for } 0.018 \le L \le 1
Inverse Transfer function:
- L = L' / 4.5 for L' < 0.081
+.. math::
- L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081
+ L = \frac{L'}{4.5} \text{, for } L' < 0.081
+
+ L = \left( \frac{L' + 0.099}{1.099}\right) ^{\frac{1}{0.45} }\text{, for } L' \ge 0.081
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_601`` encoding:
- Y' = 0.299R' + 0.587G' + 0.114B'
+.. math::
- Cb = -0.169R' - 0.331G' + 0.5B'
+ Y' = 0.2990R' + 0.5870G' + 0.1140B'
- Cr = 0.5R' - 0.419G' - 0.081B'
+ Cb = -0.1687R' - 0.3313G' + 0.5B'
+
+ Cr = 0.5R' - 0.4187G' - 0.0813B'
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. The Y'CbCr quantization is limited range. This transform is
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
.. flat-table:: EBU Tech. 3213 Chromaticities
:header-rows: 1
:stub-columns: 0
:widths: 1 1 2
-
- - .. row 1
-
- - Color
-
- - x
-
- - y
-
- - .. row 2
-
- - Red
-
- - 0.64
-
- - 0.33
-
- - .. row 3
-
- - Green
-
- - 0.29
-
- - 0.60
-
- - .. row 4
-
- - Blue
-
- - 0.15
-
- - 0.06
-
- - .. row 5
-
- - White Reference (D65)
-
- - 0.3127
-
- - 0.3290
+ * - Color
+ - x
+ - y
+ * - Red
+ - 0.64
+ - 0.33
+ * - Green
+ - 0.29
+ - 0.60
+ * - Blue
+ - 0.15
+ - 0.06
+ * - White Reference (D65)
+ - 0.3127
+ - 0.3290
The transfer function was never properly defined for this colorspace.
The Rec. 709 transfer function is recommended in the literature:
- L' = 4.5L for 0 ≤ L < 0.018
+.. math::
- L' = 1.099L :sup:`0.45` - 0.099 for 0.018 ≤ L ≤ 1
+ L' = 4.5L\text{, for } 0 \le L < 0.018
+
+ L' = 1.099L ^{0.45} - 0.099\text{, for } 0.018 \le L \le 1
Inverse Transfer function:
- L = L' / 4.5 for L' < 0.081
+.. math::
+
+ L = \frac{L'}{4.5} \text{, for } L' < 0.081
- L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081
+ L = \left(\frac{L' + 0.099}{1.099} \right) ^{\frac{1}{0.45} }\text{, for } L' \ge 0.081
The luminance (Y') and color difference (Cb and Cr) are obtained with
the following ``V4L2_YCBCR_ENC_601`` encoding:
- Y' = 0.299R' + 0.587G' + 0.114B'
+.. math::
- Cb = -0.169R' - 0.331G' + 0.5B'
+ Y' = 0.2990R' + 0.5870G' + 0.1140B'
- Cr = 0.5R' - 0.419G' - 0.081B'
+ Cb = -0.1687R' - 0.3313G' + 0.5B'
+
+ Cr = 0.5R' - 0.4187G' - 0.0813B'
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. The Y'CbCr quantization is limited range. This transform is
with full range quantization where Y' is scaled to [0…255] and Cb/Cr are
scaled to [-128…128] and then clipped to [-128…127].
-.. note:: The JPEG standard does not actually store colorspace
+.. note::
+
+ The JPEG standard does not actually store colorspace
information. So if something other than sRGB is used, then the driver
will have to set that information explicitly. Effectively
``V4L2_COLORSPACE_JPEG`` can be considered to be an abbreviation for
projects / cascardo / linux.git / blobdiff