Converting Between YUV and RGB

最新推荐文章于 2021-05-27 05:59:16 发布

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本文详细介绍了YUV与RGB格式之间的转换方法，包括从RGB到YUV的转换公式及从YUV到RGB的转换过程，同时提供了转换过程中需要注意的关键点。

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.

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