Shake - Convolve

Convolve

Function

The Convolve function allows you to enter your own custom filter. Standard filters are in your include/nreal.h file, and consist of sharpen, edge3x3, edge5x5, blur3x3, blur5x5, and laplace. You can use these or use them as a model to create your own. Just place the filters in a standard plug-ins file. There is an example below.

Parameters	Type	Defaults	Function
channels	string	"rgba"	The channels on which the filter is applied.
kernel	string	"blur3x3"	blur3x3: A 3x3 pixel blur. blur5x5: A 5x5 pixel blur sharpen: Uh, sharpening... edge3x3: A 3x3 pixel edge detection. edge5x5: A 5x5 pixel edge detection. laplace: Edge detection.
percent	float	100	The mixing percent between the modified image and the original image.
absolute	int	0	Some filters return negative values. By turning on absolute, they will be inverted to positive values.

Synopsis

image Convolve( image, 
  const char * channels, 
  const char * kernel, 
  float percent,
  int absolute
);

Script

image = Convolve( 
  image, 
  "channels", 
  "kernel", 
  percent, 
  absolute
);

Command Line

shake -convolve rgba kernel percent

Example

shake lisa.iff -convolve
shake lisa.iff -convolve rgb edge3x3

Example:

Here is an example kernel. These are placed by default in the include/nreal.h file, but may also be placed in any file as you place a macro, i.e. in include/startup/my_file.h.

The first parameter is the kernel name, enclosed in quotes.
The second is the kernel size, in this case, 5x5
The third number is the gain factor. Each number is multiplied by this number, so 1 means no change.
The fourth number is the offset, which is added to the result before it is clamped/quantized. 0 means no offset.

DefKernel(
    "edge5x5",
    5, 5,
    1,
    0,
    -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1,
    -1, -1, 24, -1, -1,
    -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1
);

shake -convolve rgba edge5x5 100

See Also
Blur, Sharpen, Emboss, Median