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Misc thinning fixes. #3743

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merged 2 commits into from
May 30, 2024
Merged

Misc thinning fixes. #3743

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2c237bb
Misc thinning fixes.
vrabaud May 24, 2024
270fcd1
Use absdiff to avoid saturation
vrabaud May 28, 2024
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11 changes: 9 additions & 2 deletions modules/ximgproc/src/thinning.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -96,6 +96,10 @@ static void thinningIteration(Mat img, int iter, int thinningType){
Mat marker = Mat::zeros(img.size(), CV_8UC1);
int rows = img.rows;
int cols = img.cols;
marker.col(0).setTo(1);
marker.col(cols - 1).setTo(1);
marker.row(0).setTo(1);
marker.row(rows - 1).setTo(1);

if(thinningType == THINNING_ZHANGSUEN){
marker.forEach<uchar>([=](uchar& value, const int postion[]) {
Expand Down Expand Up @@ -133,6 +137,7 @@ static void thinningIteration(Mat img, int iter, int thinningType){
//int m1 = iter == 0 ? (p2 * p4 * p6) : (p2 * p4 * p8);
//int m2 = iter == 0 ? (p4 * p6 * p8) : (p2 * p6 * p8);
//if (A == 1 && (B >= 2 && B <= 6) && m1 == 0 && m2 == 0) value = 0;
// else value = 1;
});
}
if(thinningType == THINNING_GUOHALL){
Expand Down Expand Up @@ -170,6 +175,7 @@ static void thinningIteration(Mat img, int iter, int thinningType){
//int N = N1 < N2 ? N1 : N2;
//int m = iter == 0 ? ((p6 | p7 | (!p9)) & p8) : ((p2 | p3 | (!p5)) & p4);
//if ((C == 1) && ((N >= 2) && ((N <= 3)) & (m == 0))) value = 0;
// else value = 1;
});
}

Expand All @@ -183,16 +189,17 @@ void thinning(InputArray input, OutputArray output, int thinningType){
// Enforce the range of the input image to be in between 0 - 255
processed /= 255;

Mat prev = Mat::zeros(processed.size(), CV_8UC1);
Mat prev = processed.clone();
Mat diff;

do {
thinningIteration(processed, 0, thinningType);
thinningIteration(processed, 1, thinningType);
absdiff(processed, prev, diff);
if (!hasNonZero(diff)) break;
processed.copyTo(prev);
}
while (countNonZero(diff) > 0);
while (true);

processed *= 255;

Expand Down
17 changes: 11 additions & 6 deletions modules/ximgproc/test/test_thinning.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,12 @@

namespace opencv_test { namespace {

static int createTestImage(Mat& src)
static int createTestImage(Mat1b& src)
{
src = Mat::zeros(Size(256, 256), CV_8UC1);
src = Mat1b::zeros(Size(256, 256));
// Create a corner point that should not be affected.
src(0, 0) = 255;

for (int x = 50; x < src.cols - 50; x += 50)
{
cv::circle(src, Point(x, x/2), 30 + x/2, Scalar(255), 5);
Expand All @@ -20,13 +23,14 @@ static int createTestImage(Mat& src)

TEST(ximgproc_Thinning, simple_ZHANGSUEN)
{
Mat src;
Mat1b src;
int src_pixels = createTestImage(src);

Mat dst;
Mat1b dst;
thinning(src, dst, THINNING_ZHANGSUEN);
int dst_pixels = countNonZero(dst);
EXPECT_LE(dst_pixels, src_pixels);
EXPECT_EQ(dst(0, 0), 255);

#if 0
imshow("src", src); imshow("dst", dst); waitKey();
Expand All @@ -35,13 +39,14 @@ TEST(ximgproc_Thinning, simple_ZHANGSUEN)

TEST(ximgproc_Thinning, simple_GUOHALL)
{
Mat src;
Mat1b src;
int src_pixels = createTestImage(src);

Mat dst;
Mat1b dst;
thinning(src, dst, THINNING_GUOHALL);
int dst_pixels = countNonZero(dst);
EXPECT_LE(dst_pixels, src_pixels);
EXPECT_EQ(dst(0, 0), 255);

#if 0
imshow("src", src); imshow("dst", dst); waitKey();
Expand Down
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