Gaussian Blur Filters

Gaussian blur image filters. More...

Functions
SIMD_API void	SimdGaussianBlur3x3 (const uint8_t *src, size_t srcStride, size_t width, size_t height, size_t channelCount, uint8_t *dst, size_t dstStride)
	Performs Gaussian blur filtration with window 3x3. More...
SIMD_API void *	SimdGaussianBlurInit (size_t width, size_t height, size_t channels, const float *sigma, const float *epsilon)
	Creates Gaussian blur filter context. More...
SIMD_API void	SimdGaussianBlurRun (const void *filter, const uint8_t *src, size_t srcStride, uint8_t *dst, size_t dstStride)
	Performs image Gaussian bluring. More...

Detailed Description

Gaussian blur image filters.

Function Documentation

SimdGaussianBlur3x3()

void SimdGaussianBlur3x3	(	const uint8_t *	src,
		size_t	srcStride,
		size_t	width,
		size_t	height,
		size_t	channelCount,
		uint8_t *	dst,
		size_t	dstStride
	)

Performs Gaussian blur filtration with window 3x3.

For every point:

dst[x, y] = (src[x-1, y-1] + 2*src[x, y-1] + src[x+1, y-1] +
            2*(src[x-1, y] + 2*src[x, y] + src[x+1, y]) +
            src[x-1, y+1] + 2*src[x, y+1] + src[x+1, y+1] + 8) / 16;

All images must have the same width, height and format (8-bit gray, 16-bit UV, 24-bit BGR or 32-bit BGRA).

Note

This function has a C++ wrapper Simd::GaussianBlur3x3(const View<A>& src, View<A>& dst).

Parameters

[in]	src	- a pointer to pixels data of source image.
[in]	srcStride	- a row size of the src image.
[in]	width	- an image width.
[in]	height	- an image height.
[in]	channelCount	- a channel count.
[out]	dst	- a pointer to pixels data of destination image.
[in]	dstStride	- a row size of the dst image.

SimdGaussianBlurInit()

void * SimdGaussianBlurInit	(	size_t	width,
		size_t	height,
		size_t	channels,
		const float *	sigma,
		const float *	epsilon
	)

Creates Gaussian blur filter context.

In particular calculates Gaussian blur coefficients:

half = floor(sqrt(log(1/epsilon)) * sigma);
weight[2*half + 1];

for(x = -half; x <= half; ++x)
    weight[x + half] = exp(-sqr(x / sigma) / 2);

sum = 0;
for (x = -half; x <= half; ++x)
    sum += weight[x + half];

for (x = -half; x <= half; ++x)
    weight[x + half] /= sum;

Parameters

[in]	width	- a width of input and output image.
[in]	height	- a height of input and output image.
[in]	channels	- a channel number of input and output image. Its value must be in range [1..4].
[in]	sigma	- a pointer to sigma parameter (blur radius). Its value must be greater than 0.000001.
[in]	epsilon	- a pointer to epsilon parameter (permissible relative error). Its value must be greater than 0.000001. Pointer can be NULL and by default value 0.001 is used.

Returns

a pointer to filter context. On error it returns NULL. This pointer is used in functions SimdGaussianBlurRun. It must be released with using of function SimdRelease.

SimdGaussianBlurRun()

void SimdGaussianBlurRun	(	const void *	filter,
		const uint8_t *	src,
		size_t	srcStride,
		uint8_t *	dst,
		size_t	dstStride
	)

Performs image Gaussian bluring.

Bluring algorithm for every point:

sum = 0;
for(x = -half; x <= half; ++x)
{
    sx = min(max(0, dx + x), width - 1);
    for(y = -half; y <= half; ++y)
    {
        sy = min(max(0, dy + y), height - 1);
        sum += src[sx, sy]*weight[x + half]*weight[y + half];
    }
}
dst[dx, dy] = sum;

Parameters

[in]	filter	- a filter context. It must be created by function SimdGaussianBlurInit and released by function SimdRelease.
[in]	src	- a pointer to pixels data of the original input image.
[in]	srcStride	- a row size (in bytes) of the input image.
[out]	dst	- a pointer to pixels data of the filtered output image.
[in]	dstStride	- a row size (in bytes) of the output image.