4.7 Blur
函数
(flomap-gaussian-blur fm xσ [yσ]) → flomap
fm : flomap xσ : Real yσ : Real = xσ
Returns fm convolved, per-component, with an axis-aligned Gaussian kernel with standard deviations xσ and yσ.
If perfect Gaussian blur is not important, use flomap-blur instead, which approximates Gaussian blur closely and is faster.
例如：
> (flomap->bitmap (flomap-gaussian-blur (flomap-inset fm 12) 4))
> (flomap->bitmap (flomap-gaussian-blur (flomap-inset fm 12 3) 4 1))
函数
(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.
例如：
> (flomap->bitmap (flomap-gaussian-blur-x (flomap-inset fm 12 0) 4))
函数
(flomap-gaussian-blur-y fm σ) → flomap
fm : flomap σ : Real
Like flomap-gaussian-blur-x, but per-column instead of per-row.
函数
(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.
例如：
> (flomap->bitmap (flomap-box-blur (flomap-inset fm 4) 4))
> (flomap->bitmap (flomap-box-blur (flomap-inset fm 4 1) 4 1))
函数
(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.
例如：
> (flomap->bitmap (flomap-box-blur-x (flomap-inset fm 4 0) 4))
函数
(flomap-box-blur-y fm radius) → flomap
fm : flomap radius : Real
Like flomap-box-blur-x, but per-column instead of per-row.
函数
(flomap-blur fm xσ [yσ]) → flomap
fm : flomap xσ : Real yσ : Real = xσ
Gaussian blur, as it is implemented by flomap-gaussian-blur, is O(xσ + yσ) for any fixed flomap size.
On the other hand, flomap-blur is O(1) for the same size.
例如：
> (define gauss-blur-fm (time (flomap-gaussian-blur fm 12))) cpu time: 892 real time: 344 gc time: 0
> (define blur-fm (time (flomap-blur fm 12))) cpu time: 202 real time: 60 gc time: 0
> (flomap-extreme-values (fmsqr (fm- gauss-blur-fm blur-fm)))
0.0
0.0031721674640532663
函数
(flomap-blur-x fm xσ) → flomap
fm : flomap xσ : Real
Like flomap-blur, but blurs per-row only.
函数
(flomap-blur-y fm yσ) → flomap
fm : flomap yσ : Real
Like flomap-blur, but blurs per-column only.