前面介绍过两种调色的滤镜之后,相信大家对调色也有了一点认知,并且也能做一些并不是很艺术的技术化的调色了,这回再介绍一个调色滤镜,colorchannelmixer,看滤镜名称很显然是做色彩通道混合用的滤镜,例如在红色通道增加绿色增益、蓝色增益、红色增益、alpha增益的,下面看一下参数说明。
StevenLiu:ffmpeg StevenLiu$ ffmpeg -hide_banner -h filter=colorchannelmixer
Filter colorchannelmixer
Adjust colors by mixing color channels.
slice threading supported
Inputs:
#0: default (video)
Outputs:
#0: default (video)
colorchannelmixer AVOptions:
rr <double> ..FV..... set the red gain for the red channel (from -2 to 2) (default 1)
rg <double> ..FV..... set the green gain for the red channel (from -2 to 2) (default 0)
rb <double> ..FV..... set the blue gain for the red channel (from -2 to 2) (default 0)
ra <double> ..FV..... set the alpha gain for the red channel (from -2 to 2) (default 0)
gr <double> ..FV..... set the red gain for the green channel (from -2 to 2) (default 0)
gg <double> ..FV..... set the green gain for the green channel (from -2 to 2) (default 1)
gb <double> ..FV..... set the blue gain for the green channel (from -2 to 2) (default 0)
ga <double> ..FV..... set the alpha gain for the green channel (from -2 to 2) (default 0)
br <double> ..FV..... set the red gain for the blue channel (from -2 to 2) (default 0)
bg <double> ..FV..... set the green gain for the blue channel (from -2 to 2) (default 0)
bb <double> ..FV..... set the blue gain for the blue channel (from -2 to 2) (default 1)
ba <double> ..FV..... set the alpha gain for the blue channel (from -2 to 2) (default 0)
ar <double> ..FV..... set the red gain for the alpha channel (from -2 to 2) (default 0)
ag <double> ..FV..... set the green gain for the alpha channel (from -2 to 2) (default 0)
ab <double> ..FV..... set the blue gain for the alpha channel (from -2 to 2) (default 0)
aa <double> ..FV..... set the alpha gain for the alpha channel (from -2 to 2) (default 1)
This filter has support for timeline through the 'enable' option.
调整视频色彩的话,设置这些参数之后,有一个计算的公式:
红色部分:
red=red*rr + blue*rb + green*rg + alpha*ra
绿色部分:
green=red*gr + blue*gb + green*gg + alpha*ga
蓝色部分:
blue=red*br + blue*bb + green*bg + alpha*ba
Alpha部分:
alpha=red*ar + blue*ab + green*ag + alpha*aa
公式了解过了,下面看一下设一下测试的值,看看效果,首先还是拿开放版权的视频测试,争取不侵权,看一下原图像是什么样的。
![图片](https://www.nxrte.com/wp-content/themes/justnews/themer/assets/images/lazy.png)
图像看上去挺棒的,一切正常,那么我们先调一下红色通道部分,看一下会变成什么样。
ffplay -vf colorchannelmixer=rr=0.393:rg=0.769:rb=0.189:ra=0 graded_edit_final_00668.png
看一下效果
![图片](https://www.nxrte.com/wp-content/themes/justnews/themer/assets/images/lazy.png)
颜色整体稍微偏褐色那么了一点,看来是有效果。如果把整体调整得大红色,可以试着这么干,把green和blue通道全部设置0,红色通道全部最大:
ffplay -vf colorchannelmixer=rr=2:rg=2:rb=2:ra=0:gr=0:gg=0:gb=0:br=0:bg=0:bb=0 graded_edit_final_00668.png
看一下效果,确认一下是不是如我们所设置的值对应:
![图片](https://www.nxrte.com/wp-content/themes/justnews/themer/assets/images/lazy.png)
当然,如果这只偏蓝色一点的话,可以这么设置:
ffplay -vf colorchannelmixer=br=0.393:bg=0.769:bb=0.189:ba=0 graded_edit_final_00668.png
看一下效果:
![图片](https://www.nxrte.com/wp-content/themes/justnews/themer/assets/images/lazy.png)
做一些基本的调色,用colorchannelmixer基本上可以做到微调色了,效果能好很多。
至于调API设置,可以参考《使用 FFmpeg 实现画中画效果》
方法都是相通的。
这一次就介绍到这里,更多的colorchannelmixer的使用方式欢迎随时交流。
作者:悟空 公众号:流媒体技术
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