On this page:
flomap-gaussian-blur
flomap-gaussian-blur-x
flomap-gaussian-blur-y
flomap-box-blur
flomap-box-blur-x
flomap-box-blur-y
flomap-blur
flomap-blur-x
flomap-blur-y

4.7 Blur

procedure

(flomap-gaussian-blur fm  [])  flomap

  fm : flomap
   : Real
   : Real = 
Returns fm convolved, per-component, with an axis-aligned Gaussian kernel with standard deviations and .

If perfect Gaussian blur is not important, use flomap-blur instead, which approximates Gaussian blur closely and is faster.

Examples:

procedure

(flomap-gaussian-blur-x fm σ)  flomap

  fm : flomap
  σ : Real
Returns fm convolved, per-component and per-row, with a Gaussian kernel with standard deviation σ.

If perfect Gaussian blur is not important, use flomap-blur-x instead, which approximates Gaussian blur closely and is usually much faster.

Example:

procedure

(flomap-gaussian-blur-y fm σ)  flomap

  fm : flomap
  σ : Real
Like flomap-gaussian-blur-x, but per-column instead of per-row.

procedure

(flomap-box-blur fm x-radius [y-radius])  flomap

  fm : flomap
  x-radius : Real
  y-radius : Real = x-radius
Returns fm convolved, per-component, with a box kernel with radii x-radius and y-radius. The radii are of the largest axis-aligned ellipse that would fit in the box.

Examples:

procedure

(flomap-box-blur-x fm radius)  flomap

  fm : flomap
  radius : Real
Returns fm convolved, per-component and per-row, with a box kernel with radius radius.

Example:

procedure

(flomap-box-blur-y fm radius)  flomap

  fm : flomap
  radius : Real
Like flomap-box-blur-x, but per-column instead of per-row.

procedure

(flomap-blur fm  [])  flomap

  fm : flomap
   : Real
   : Real = 
Returns approximately the result of (flomap-gaussian-blur fm ).

Gaussian blur, as it is implemented by flomap-gaussian-blur, is O( + ) for any fixed flomap size. On the other hand, flomap-blur is O(1) for the same size.

Examples:
> (define gauss-blur-fm (time (flomap-gaussian-blur fm 12)))

cpu time: 1854 real time: 247 gc time: 45

> (define blur-fm (time (flomap-blur fm 12)))

cpu time: 3312 real time: 471 gc time: 170

> (flomap-extreme-values
   (fmsqr (fm- gauss-blur-fm blur-fm)))

0.0

0.0031721674640532663

procedure

(flomap-blur-x fm )  flomap

  fm : flomap
   : Real
Like flomap-blur, but blurs per-row only.

procedure

(flomap-blur-y fm )  flomap

  fm : flomap
   : Real
Like flomap-blur, but blurs per-column only.