History of 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