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Merge pull request #16194 from alalek:fix_16192

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* imgproc(test): resize(LANCZOS4) reproducer 16192

* imgproc: fix resize LANCZOS4 coefficients generation
This commit is contained in:
Alexander Alekhin 2019-12-19 13:20:42 +03:00 committed by GitHub
parent 5bf7345743
commit 4733a19bab
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 26 additions and 10 deletions
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23
modules/imgproc/src/resize.cpp
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@ -920,20 +920,23 @@ static inline void interpolateLanczos4( float x, float* coeffs )
static const double cs[][2]=
{{1, 0}, {-s45, -s45}, {0, 1}, {s45, -s45}, {-1, 0}, {s45, s45}, {0, -1}, {-s45, s45}};
if( x < FLT_EPSILON )
{
for( int i = 0; i < 8; i++ )
coeffs[i] = 0;
coeffs[3] = 1;
return;
}
float sum = 0;
double y0=-(x+3)*CV_PI*0.25, s0 = std::sin(y0), c0= std::cos(y0);
for(int i = 0; i < 8; i++ )
{
double y = -(x+3-i)*CV_PI*0.25;
coeffs[i] = (float)((cs[i][0]*s0 + cs[i][1]*c0)/(y*y));
float y0_ = (x+3-i);
if (fabs(y0_) >= 1e-6f)
{
double y = -y0_*CV_PI*0.25;
coeffs[i] = (float)((cs[i][0]*s0 + cs[i][1]*c0)/(y*y));
}
else
{
// special handling for 'x' values:
// - ~0.0: 0 0 0 1 0 0 0 0
// - ~1.0: 0 0 0 0 1 0 0 0
coeffs[i] = 1e30f;
}
sum += coeffs[i];
}

13
modules/imgproc/test/test_imgwarp.cpp
View File

@ -1708,6 +1708,19 @@ TEST(Resize, Area_half)
}
}
TEST(Resize, lanczos4_regression_16192)
{
Size src_size(11, 17);
Size dst_size(11, 153);
Mat src(src_size, CV_8UC3, Scalar::all(128));
Mat dst(dst_size, CV_8UC3, Scalar::all(255));
cv::resize(src, dst, dst_size, 0, 0, INTER_LANCZOS4);
Mat expected(dst_size, CV_8UC3, Scalar::all(128));
EXPECT_EQ(cvtest::norm(dst, expected, NORM_INF), 0) << dst(Rect(0,0,8,8));
}
TEST(Imgproc_Warp, multichannel)
{
static const int inter_types[] = {INTER_NEAREST, INTER_AREA, INTER_CUBIC,