GeneralConvolution

2018-10-06T20:02:15Z

Chanijean: /* External Links */ link is back up :^)

Performs a matrix convolution on an [[RGB32]] clip.

== Syntax and Parameters ==
<div style="max-width:68em" >
{{Template:FuncDef
|GeneralConvolution (clip ''clip'', [ int ''bias'', string ''matrix'', float ''divisor'', bool ''auto'' ] )
}}

:{{Par2|clip|clip|}}
::Source clip. Must be [[RGB32]].

:{{Par2|bias|int|0}}
::Additive bias to adjust the total output intensity.

:{{Par2|matrix|string|"0 0 0 0 1 0 0 0 0"}}
::A 3×3 or 5×5 matrix with 3<sup>2</sup> (9) or 5<sup>2</sup> (25) integer values.

:{{Par2|divisor|float|1.0}}
::Divides the output of the convolution before adding {{FuncArg|bias}}.

:{{Par2|auto|bool|true}}
::Enables ''auto scaling''. Auto scaling divides the output of the convolution by the sum of the elements of the matrix. The value of {{FuncArg|divisor}} is applied in addition to this auto scaling factor. If the sum of elements is zero, auto scaling is disabled.

The {{FuncArg|divisor}} is usually the sum of the elements of the matrix. But when the sum is zero, you can leave {{FuncArg|divisor}}=1 and use the {{FuncArg|bias}} setting to correct the pixel values. The {{FuncArg|bias}} could be useful if the pixel values are negative due to the convolution. After adding {{FuncArg|bias}}, the pixels are clipped to the range 0-255.

Around the borders the edge pixels are simply repeated to service the matrix.
</div>

== Examples ==
* Blur:
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
10 10 10 10 10
10 10 10 10 10
10 10 16 10 10
10 10 10 10 10
10 10 10 10 10 ", 256, false)
</div>
{{HalfBreak}}
* Horizontal (Sobel) edge detection:
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
1 2 1
0 0 0
-1 -2 -1 ", 8)
</div>
{{HalfBreak}}
* Vertical (Sobel) Edge Detection:
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
1 0 -1
2 0 -2
1 0 -1 ", 8)
</div>
{{HalfBreak}}
* Displacement (simply move the position of the "1" for left, right, up, down)
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
0 1 0
0 0 0
0 0 0 ")
</div>
{{HalfBreak}}
* Displacement by half pixel up (auto scaling):
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
0 1 0
0 1 0
0 0 0 ")
</div>
{{HalfBreak}}
* Displacement by half pixel to the right (manual scaling):
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
0 0 0
0 128 128
0 0 0 ", 256, false)
</div>
{{HalfBreak}}
* Sharpness filter:
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(0, "
0 -1 0
-1 5 -1
0 -1 0 ", 0, true)
</div>
:In this case, the new pixel values <span style="font-family:times,georgia,serif;">y(m,n)</span> are given by
:<span style="font-family:times,georgia,serif;">y(m,n) = ( -1*x(m-1,n) - 1*x(m,n-1) + 5*x(m,n) - 1*x(m,n+1) - 1*x(m+1,n) )/1.0 + 0</span>
{{HalfBreak}}
* Slight blur filter with black level clipping and 25% brightening:
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(-16, "
0 12 0
12 256 12
0 12 0 ", 0.75 ,true)
</div>
:In this case, the new pixel values <span style="font-family:times,georgia,serif;">y(m,n)</span> are given by
:<span style="font-family:times,georgia,serif;">y(m,n) = ( 12*x(m-1,n) + 12*x(m,n-1) + 256*x(m,n) + 12*x(m,n+1) + 12*x(m+1,n) )/(12+12+256+12+12)/0.75 - 16</span>
{{HalfBreak}}
* Emboss filter (3D relief effect)
<div {{BoxWidthIndent|28|2}} >
GeneralConvolution(128, "
-1 0 0
0 0 0
0 0 1")
</div>

== External Links ==
* [https://jeanbruenn.info/2011/03/13/avisynths-convolution-stuff-explained/ ''AviSynth’s GeneralConvolution explained'']
* Some other examples can be found [http://web.archive.org/web/20100105183639/http://www.gamedev.net/reference/programming/features/imageproc/page2.asp here].

== Changelog ==
{| border="1"
|-
| v2.55
| Added divisor, auto.
|-
| v2
| Initial Release
|}

[[Category:Internal filters]]
[[Category:Blurring]]
[[Category:Sharpeners]]

Avisynth wiki - User contributions [en]

GeneralConvolution