OPENCV学习一（滤波）

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opencv中常见的4种滤波算有均值滤波，高斯滤波，中值滤波，双边滤波。

双边滤波：

/****************************************************************************************\
Bilateral Filtering
\****************************************************************************************/
namespace cv
{
static void
bilateralFilter_8u( const Mat& src, Mat& dst, int d,
double sigma_color, double sigma_space,
int borderType )
{
int cn = src.channels();
int i, j, k, maxk, radius;
Size size = src.size();
CV_Assert( (src.type() == CV_8UC1 || src.type() == CV_8UC3) &&
src.type() == dst.type() && src.size() == dst.size() &&
src.data != dst.data );
if( sigma_color <= 0 )
sigma_color = 1;
if( sigma_space <= 0 )
sigma_space = 1;
double gauss_color_coeff = -0.5/(sigma_color*sigma_color);
double gauss_space_coeff = -0.5/(sigma_space*sigma_space);
if( d <= 0 )
radius = cvRound(sigma_space*1.5);
else
radius = d/2;
radius = MAX(radius, 1);
d = radius*2 + 1;
Mat temp;
copyMakeBorder( src, temp, radius, radius, radius, radius, borderType );
vector<float> _color_weight(cn*256);
vector<float> _space_weight(d*d);
vector<int> _space_ofs(d*d);
float* color_weight = &_color_weight[0];
float* space_weight = &_space_weight[0];
int* space_ofs = &_space_ofs[0];
// initialize color-related bilateral filter coefficients
for( i = 0; i < 256*cn; i++ )
color_weight[i] = (float)std::exp(i*i*gauss_color_coeff);
// initialize space-related bilateral filter coefficients
for( i = -radius, maxk = 0; i <= radius; i++ )
for( j = -radius; j <= radius; j++ )
{
double r = std::sqrt((double)i*i + (double)j*j);
if( r > radius )
continue;
space_weight[maxk] = (float)std::exp(r*r*gauss_space_coeff);
space_ofs[maxk++] = (int)(i*temp.step + j*cn);
}
for( i = 0; i < size.height; i++ )
{
const uchar* sptr = temp.data + (i+radius)*temp.step + radius*cn;
uchar* dptr = dst.data + i*dst.step;
if( cn == 1 )
{
for( j = 0; j < size.width; j++ )
{
float sum = 0, wsum = 0;
int val0 = sptr[j];
for( k = 0; k < maxk; k++ )
{
int val = sptr[j + space_ofs[k]];
float w = space_weight[k]*color_weight[std::abs(val - val0)];
sum += val*w;
wsum += w;
}
// overflow is not possible here => there is no need to use CV_CAST_8U
dptr[j] = (uchar)cvRound(sum/wsum);
}
}
else
{
assert( cn == 3 );
for( j = 0; j < size.width*3; j += 3 )
{
float sum_b = 0, sum_g = 0, sum_r = 0, wsum = 0;
int b0 = sptr[j], g0 = sptr[j+1], r0 = sptr[j+2];
for( k = 0; k < maxk; k++ )
{
const uchar* sptr_k = sptr + j + space_ofs[k];
int b = sptr_k[0], g = sptr_k[1], r = sptr_k[2];
float w = space_weight[k]*color_weight[std::abs(b - b0) +
std::abs(g - g0) + std::abs(r - r0)];
sum_b += b*w; sum_g += g*w; sum_r += r*w;
wsum += w;
}
wsum = 1.f/wsum;
b0 = cvRound(sum_b*wsum);
g0 = cvRound(sum_g*wsum);
r0 = cvRound(sum_r*wsum);
dptr[j] = (uchar)b0; dptr[j+1] = (uchar)g0; dptr[j+2] = (uchar)r0;
}
}
}
}

opencv中调用：

bilateralFilter(InputArray src, OutputArray dst, int n, double sigmaColor, double sigmaSpace,
int borderType=BORDER_DEFAULT )；

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