Color Space conversion between RGB and YCbCr

YCbCr is a revision of YUV through scaling and offset. It can be seen as a subset of YUV. It is mainly used to optimize the transmission of color video signals, so that it is backward compatible with vintage black and white TVs. Compared with RGB video signal transmission, RGB requires three independent video signals to be transmitted at the same time ).

Y: brightness (luminance or Luma), that is, the gray scale value. The "brightness" is established through the RGB input signal by overlapping specific parts of the RGB signal.

U & V: chrominance or chroma, used to describe the image color and saturation, used to specify the pixel color. "Color" defines two aspects of color-tone and saturation, expressed by Cr and CB respectively.

CB: the difference between the blue part of the RGB input signal and the brightness value of the RGB signal.
Cr: the difference between the red part of the RGB input signal and the brightness value of the RGB signal.

In the following two formulas, the values of each component of RGB and YCbCr ranges from 0 to 255.

Convert RGB to YCbCr

This formula is from: Genesis microchip. gm6010/gm6015 Programming Guide [M]. California us: Genesis Microchip Company, 2002: 85-90

| Y | 16 | 65.738, 129.057, 25.06 | r |
| CB | = | 128 | + (1/256) * |-37.945-74.494 112.43 | * | G |
| Cr | 128 | 112.439-94.154-18.28 | B |

That is:

Y = 0.257 * r + 0.564 * g + 0.098 * B + 16
CB =-0.148 * R-0.291 * g + 0.439 * B + 128
Cr = 0.439 * R-0.368 * G-0.071 * B + 128

Convert YCbCr to RGB

This formula is from: Genesis microchip. gm6015 preliminary data sheet [M]. California us: Genesis Microchip Company, 200:33-34

| R | 298.082 0 408.58 | Y-16 |
| G | = (1/256) * | 298.082-100.291-208.12 | * | CB-128 |
| B | 298.082 516.411 0 | Cr-128 |

That is:

R = 1.164 * (Y-16) + 1.596 * (Cr-128)
G = 1.164*(Y-16)-0.392*(CB-128)-0.813 * (Cr-128)
B = 1.164 * (Y-16) + 2.017 * (CB-128)

 

From: http://estray2wandering.blogbus.com/logs/100329876.html