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last update 20 Sep 2009 |
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#include <cvrSplitImageToYUV.h>
Public Member Functions | |
| splitImageToYUV () | |
| splitImageToYUV (const splitImageToYUV &other) | |
| virtual | ~splitImageToYUV () |
| const std::string & | name () const |
| splitImageToYUV & | copy (const splitImageToYUV &other) |
| splitImageToYUV & | operator= (const splitImageToYUV &other) |
| virtual splitImageToYUV * | clone () const |
| virtual splitImageToYUV * | newInstance () const |
| virtual bool | apply (const rgbaPixel &pixel, float &c1, float &c2, float &c3) const |
| virtual bool | apply (const rgbaPixel &pixel, ubyte &c1, ubyte &c2, ubyte &c3) const |
| virtual bool | apply (const matrix< rgbaPixel > &img, matrix< float > &c1, matrix< float > &c2, matrix< float > &c3) const |
| virtual bool | apply (const matrix< rgbaPixel > &img, matrix< ubyte > &c1, matrix< ubyte > &c2, matrix< ubyte > &c3) const |
In the literature, technical and scientific, there is a confusion between the color spaces YUV, YCrCb and YPbPr. Poynton in http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html explains that YUV is usually never correctly meant, because the color space normally used for component digital video is the YCrCb (ITU-RS601 or CCIR-601). Other devices use the YPbPr, but the "real" YUV is usually not employed.
The CVR-Lib provides all three spaces:
This functor splits an RGB images into the color space YUV as described in the Poynton reference given above.
![\[ \begin{bmatrix} Y \\ U \\ V \end{bmatrix} = \begin{bmatrix} 0.299 & 0.587 & 0.114 \\ -0.147141189 & -0.288869157 & 0.436010346 \\ 0.614975383 & -0.514965121 & -0.100010262 \end{bmatrix} \begin{bmatrix} R \\ G \\ B \end{bmatrix} \]](form_42.png)
Here, RGB are values in the intervall [0,1]. Within this range, the excursion for Y is also from 0.0 to 1.0, the excursion of U is from -0.436 to 0.436 and V varies from -0.615 to 0.615. These ranges are respected in the implentation for float types (cvr::channel).
If you use ubyte (cvr::matrix<ubyte>), then the values for U and V are linearly mapped from 0 to 1, which results in the mapping
Y = 0.299*R + 0.587*G + 0.114*B U = -0.169*R - 0.331*G + 0.500*B + 128.0 V = 0.500*R - 0.419*G - 0.081*B + 128.0
The former mapping is equivalent to the color space YPbPr scaled in such a way that "black" is mapped to Y=0 and "white" to Y=255, and the Pb and Pr channels, which acquire values from -0.5 to 0.5, are linearly mapped to the inteval [0,255] as well. In other words, for ubyte operations it is equivalent to use this functor or cvr::splitImageToYPbPr (which is maybe better named as the value ratios are at least kept there).
| cvr::splitImageToYUV::splitImageToYUV | ( | ) |
default constructor
| cvr::splitImageToYUV::splitImageToYUV | ( | const splitImageToYUV & | other | ) |
| virtual cvr::splitImageToYUV::~splitImageToYUV | ( | ) | [virtual] |
destructor
| virtual bool cvr::splitImageToYUV::apply | ( | const matrix< rgbaPixel > & | img, | |
| matrix< ubyte > & | c1, | |||
| matrix< ubyte > & | c2, | |||
| matrix< ubyte > & | c3 | |||
| ) | const [virtual] |
Split image into 8-bit channels.
N.B.: when casting the transformation result to unsigned shorts (8-bit channel) major rounding errors will occur.
As a result, the merging operation might produce negative values or values > 1, which are truncated subsequently. When accurate Y, U and V values are required, prefer float values.
| virtual bool cvr::splitImageToYUV::apply | ( | const matrix< rgbaPixel > & | img, | |
| matrix< float > & | c1, | |||
| matrix< float > & | c2, | |||
| matrix< float > & | c3 | |||
| ) | const [virtual] |
split pixel into float channels
| virtual bool cvr::splitImageToYUV::apply | ( | const rgbaPixel & | pixel, | |
| ubyte & | c1, | |||
| ubyte & | c2, | |||
| ubyte & | c3 | |||
| ) | const [inline, virtual] |
Split pixel into 8-bit values (between 0 and 255).
N.B.: when casting the transformation result to unsigned shorts (8-bit channel) major rounding errors will occur.
As a result, the merging operation might produce negative values or values > 1, which are truncated subsequently.
When accurate Y, U and V values are required, prefer float values
Implements cvr::splitImage.
| virtual bool cvr::splitImageToYUV::apply | ( | const rgbaPixel & | pixel, | |
| float & | c1, | |||
| float & | c2, | |||
| float & | c3 | |||
| ) | const [inline, virtual] |
| virtual splitImageToYUV* cvr::splitImageToYUV::clone | ( | ) | const [virtual] |
| splitImageToYUV& cvr::splitImageToYUV::copy | ( | const splitImageToYUV & | other | ) |
| const std::string& cvr::splitImageToYUV::name | ( | ) | const [virtual] |
| virtual splitImageToYUV* cvr::splitImageToYUV::newInstance | ( | ) | const [virtual] |
| splitImageToYUV& cvr::splitImageToYUV::operator= | ( | const splitImageToYUV & | other | ) |