牵着老婆满街逛

严以律己,宽以待人. 三思而后行.
GMail/GTalk: yanglinbo#google.com;
MSN/Email: tx7do#yahoo.com.cn;
QQ: 3 0 3 3 9 6 9 2 0 .

Converting Between YUV and RGB

转载自:http://msdn.microsoft.com/en-us/library/ms893078.aspx

It is frequently necessary to convert between YUV pixel formats (used by the JPEG and MPEG compression methods) and RGB format (used by many hardware manufacturers.) The following formulas show how to compute a pixel's value in one format from the pixel value in the other format.

YUV format allows for higher compression rates without a proportionately high loss of data, as the U and V portions can be highly compressed and computed from the non- or lowly-compressed Y portion.

Computer RGB888, or full-scale RGB, uses 8 bits each for the red, green, and blue channels. Black is represented by R = G = B = 0, and white is represented by R = G = B = 255. The 4:4:4 YUV format uses 8 bits each for the Y, U, and V channels.

Converting RGB888 to YUV

The following formulas define the conversion from RGB to YUV:

Y = ( (  66 * R + 129 * G +  25 * B + 128) >> 8) +  16
U = ( ( -38 * R -  74 * G + 112 * B + 128) >> 8) + 128
V = ( ( 112 * R -  94 * G -  18 * B + 128) >> 8) + 128

These formulas produce 8-bit results using coefficients that require no more than 8 bits of (unsigned) precision. Intermediate results require up to 16 bits of precision.

Converting 8-bit YUV to RGB888

The following coefficients are used in conversion process:

C = Y - 16
D = U - 128
E = V - 128

Using the previous coefficients and noting that clip() denotes clipping a value to the range of 0 to 255, the following formulas provide the conversion from YUV to RGB:

R = clip(( 298 * C           + 409 * E + 128) >> 8)
G = clip(( 298 * C - 100 * D - 208 * E + 128) >> 8)
B = clip(( 298 * C + 516 * D           + 128) >> 8)

These formulas use some coefficients that require more than 8 bits of precision to produce each 8-bit result, and intermediate results require more than 16 bits of precision.

Note   All units range from 0 (zero) to 1.0 (one). In DirectDraw, they range from 0 to 255. Overflow and underflow can (and does) occur, and the results must be saturated.

To convert 4:2:0 or 4:2:2 YUV to RGB, convert the YUV data to 4:4:4 YUV, and then convert from 4:4:4 YUV to RGB.


 Last updated on Thursday, April 08, 2004

© 1992-2003 Microsoft Corporation. All rights reserved.

 

posted on 2013-01-24 23:27 杨粼波 阅读(360) 评论(0)  编辑 收藏 引用


只有注册用户登录后才能发表评论。
【推荐】超50万行VC++源码: 大型组态工控、电力仿真CAD与GIS源码库
网站导航: 博客园   IT新闻   BlogJava   知识库   博问   管理