Editing cnvX - FilterMeisterWiki

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= cnvX =

== Syntax ==
{{int cnvX(int k, int off, int d, function* pGetf, int x, int y, int z)}}

== Arguments ==
:'''k'''
::The kernel radius. Must be a positive number.
:'''off'''
::The starting index within the anonymous array of ((put)) / ((get)) cells where the kernel coefficients are stored. The number of coefficients is n=k*2+1, where 'k' is the kernel radius.
:'''d'''
::The denominator by which the convolution sum will be divided.
:'''pGetf'''
::The FM built-in function that will be called to fetch values from an image buffer at the designated coordinates. Must be 'src', 'tget', 't2get', or 'pget'.
:'''x'''
::The x-coordinate at which the (center of the) kernel is to be applied.
:'''y'''
::The y-coordinate at which the (center of the) kernel is to be applied.
:'''z'''
::The channel number to which the kernel is applied.

== Return ==
The integer result obtained by summing the products of the n kernel coefficients with n image pixels in the X or Y direction, and dividing the sum by 'd'.

== Description ==
Applies a 1-D convolution to the image in the horizontal / x direction.  That is, cnvX convolves pixels at co-these ordinates:
(x-k,y), (x-k+1,y), ... (x-1,y), (x,y), (x+1,y), ... (x+k-1,y), (x+k,y)

== Example ==
<code>
%fml
// 3-pixel radius blur in the x-direction

ForEveryTile: {

// Convolution co-efficients
  // in first 7 cells
  put(1, 0);
  put(2, 1);
  put(3, 2);
  put(4, 3);
  put(3, 4);
  put(2, 5);
  put(1, 6);

int val;

for (z = 0; z < 3; z++) {  
    for (y = y_start; y < y_end; y++) {  
      for (x = x_start; x < x_end; x++) { 
 
        val = cnvX(3, 0, 16, src, x, y, z);
        pset(x, y, z, val);

}
    }
  }

return true;
}
</code>

== See Also ==
((cnv)), ((cnvY)), ((xyzcnv))

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