diff --git a/12/do_sprawdzenia/cpp/corner_harris.cpp b/12/do_sprawdzenia/cpp/corner_harris.cpp
new file mode 100644
index 0000000..ae8d718
--- /dev/null
+++ b/12/do_sprawdzenia/cpp/corner_harris.cpp
@@ -0,0 +1,158 @@
+#include "corner_harris.h"
+
+#include "blur_gaussian.h"
+#include "conversion_grayscale.h"
+#include "edge_sobel.h"
+
+CornerHarris::CornerHarris(PNM* img) :
+    Convolution(img)
+{
+}
+
+CornerHarris::CornerHarris(PNM* img, ImageViewer* iv) :
+    Convolution(img, iv)
+{
+}
+
+PNM* CornerHarris::transform()
+{
+    int    threshold    = getParameter("threshold").toInt();
+    double sigma        = getParameter("sigma").toDouble();
+    double sigma_weight = getParameter("sigma_weight").toDouble();
+    double k_param      = getParameter("k").toDouble();
+
+    int width  = image->width();
+    int height = image->height();
+
+    PNM* newImage = new PNM(width, height, QImage::Format_Mono);
+
+    math::matrix<float> Ixx(width, height);
+    math::matrix<float> Iyy(width, height);
+    math::matrix<float> Ixy(width, height);
+    math::matrix<float> corner_candidates(width, height);
+    math::matrix<float> corner_nonmax_suppress(width, height);
+
+    ConversionGrayscale* conversion_grayscale = new ConversionGrayscale(image);
+    PNM* gray_image = conversion_grayscale->transform();
+
+    BlurGaussian* blur_gaussian = new BlurGaussian(gray_image);
+    blur_gaussian->setParameter("size", 3);
+    blur_gaussian->setParameter("sigma", 1.6);
+    PNM* blur_gauss_image = blur_gaussian->transform();
+
+    EdgeSobel* edge_sobel = new EdgeSobel(blur_gauss_image);
+    math::matrix<float>* Gx = edge_sobel->rawHorizontalDetection();
+    math::matrix<float>* Gy = edge_sobel->rawVerticalDetection();
+
+    for (int i = 0;  i < width; i++)
+    {
+        for (int j = 0; j < height; j++)
+        {
+            Ixx[i][j] = (*Gx)[i][j] * (*Gx)[i][j];
+            Ixy[i][j] = (*Gx)[i][j] * (*Gy)[i][j];
+            Iyy[i][j] = (*Gy)[i][j] * (*Gy)[i][j];
+
+            corner_candidates[i][j] = 0;
+            corner_nonmax_suppress[i][j] = 0;
+        }
+    }
+
+    for (int i = 1; i < width - 1; i++)
+    {
+        for (int j = 1; j < height - 1; j++)
+        {
+            float Sxx = 0;
+            float Syy = 0;
+            float Sxy = 0;
+
+            for (int k = -1; k <= 1; k++)
+            {
+                for (int l = -1; l <= 1; l++)
+                {
+                    Sxx = Sxx + Ixx[i + k][j + l] * BlurGaussian::getGauss(k, l, sigma);
+                    Syy = Syy + Iyy[i + k][j + l] * BlurGaussian::getGauss(k, l, sigma);
+                    Sxy = Sxy + Ixy[i + k][j + l] * BlurGaussian::getGauss(k, l, sigma);
+                }
+            }
+
+            Sxx = Sxx / sigma_weight;
+            Sxy = Sxy / sigma_weight;
+            Syy = Syy / sigma_weight;
+
+            math::matrix<float> H(2,2);
+
+            H(0,0) = Sxx;
+            H(0,1) = Sxy;
+            H(1,0) = Sxy;
+            H(1,1) = Syy;
+
+            float detH = H(0, 0) * H(1, 1) - H(0, 1) * H(1, 0); //determinant
+            float trH = H(0, 0) + H(1, 1); //trace
+            float r = detH - k_param * pow(trH, 2);
+
+            if (r > threshold)
+            {
+                corner_candidates[i][j] = r;
+            }
+        }
+    }
+
+    bool search = true;
+
+    while(search)
+    {
+        search = false;
+        for (int i = 1;  i < width - 1; i++)
+        {
+            for (int j = 1;  j <height - 1; j++)
+            {
+                float max = corner_candidates[i][j];
+
+                for (int k = -1; k <= 1; k++)
+                {
+                    for (int l = -1; l <= 1; l++)
+                    {
+                        if (max < corner_candidates[i+k][j+l])
+                        {
+                            max = corner_candidates[i+k][j+l];
+                        }
+                    }
+                }
+
+                if (corner_candidates[i][j] == max)
+                {
+                    corner_nonmax_suppress[i][j] = corner_candidates[i][j];
+                }
+                else
+                {
+                    if (corner_candidates[i][j] > 0)
+                    {
+                        search = true;
+                    }
+
+                    corner_nonmax_suppress[i][j] = 0;
+                }
+
+            }
+        }
+        corner_candidates = corner_nonmax_suppress;
+    }
+
+    for (int i = 0; i < width; i++)
+    {
+        for (int j = 0; j < height; j++)
+        {
+            if (corner_candidates[i][j] == 0)
+            {
+                newImage->setPixel(i, j, Qt::color0);
+            }
+            else
+            {
+                newImage->setPixel(i, j, Qt::color1);
+            }
+        }
+    }
+    return newImage;
+}
+
+
diff --git a/12/do_sprawdzenia/cpp/image1.png b/12/do_sprawdzenia/cpp/image1.png
new file mode 100644
index 0000000..80b3ea4
Binary files /dev/null and b/12/do_sprawdzenia/cpp/image1.png differ
diff --git a/app/cpp/mysimplegimp/src/core/transformations/corner_harris.cpp b/app/cpp/mysimplegimp/src/core/transformations/corner_harris.cpp
index f8979cf..ae8d718 100644
--- a/app/cpp/mysimplegimp/src/core/transformations/corner_harris.cpp
+++ b/app/cpp/mysimplegimp/src/core/transformations/corner_harris.cpp
@@ -17,16 +17,142 @@ CornerHarris::CornerHarris(PNM* img, ImageViewer* iv) :
 PNM* CornerHarris::transform()
 {
     int    threshold    = getParameter("threshold").toInt();
-    double sigma        = getParameter("sigma").toDouble(),
-           sigma_weight = getParameter("sigma_weight").toDouble(),
-           k_param      = getParameter("k").toDouble();
+    double sigma        = getParameter("sigma").toDouble();
+    double sigma_weight = getParameter("sigma_weight").toDouble();
+    double k_param      = getParameter("k").toDouble();
 
-    int width  = image->width(),
-        height = image->height();
+    int width  = image->width();
+    int height = image->height();
 
     PNM* newImage = new PNM(width, height, QImage::Format_Mono);
 
-    qDebug() << Q_FUNC_INFO << "Not implemented yet!";
+    math::matrix<float> Ixx(width, height);
+    math::matrix<float> Iyy(width, height);
+    math::matrix<float> Ixy(width, height);
+    math::matrix<float> corner_candidates(width, height);
+    math::matrix<float> corner_nonmax_suppress(width, height);
 
+    ConversionGrayscale* conversion_grayscale = new ConversionGrayscale(image);
+    PNM* gray_image = conversion_grayscale->transform();
+
+    BlurGaussian* blur_gaussian = new BlurGaussian(gray_image);
+    blur_gaussian->setParameter("size", 3);
+    blur_gaussian->setParameter("sigma", 1.6);
+    PNM* blur_gauss_image = blur_gaussian->transform();
+
+    EdgeSobel* edge_sobel = new EdgeSobel(blur_gauss_image);
+    math::matrix<float>* Gx = edge_sobel->rawHorizontalDetection();
+    math::matrix<float>* Gy = edge_sobel->rawVerticalDetection();
+
+    for (int i = 0;  i < width; i++)
+    {
+        for (int j = 0; j < height; j++)
+        {
+            Ixx[i][j] = (*Gx)[i][j] * (*Gx)[i][j];
+            Ixy[i][j] = (*Gx)[i][j] * (*Gy)[i][j];
+            Iyy[i][j] = (*Gy)[i][j] * (*Gy)[i][j];
+
+            corner_candidates[i][j] = 0;
+            corner_nonmax_suppress[i][j] = 0;
+        }
+    }
+
+    for (int i = 1; i < width - 1; i++)
+    {
+        for (int j = 1; j < height - 1; j++)
+        {
+            float Sxx = 0;
+            float Syy = 0;
+            float Sxy = 0;
+
+            for (int k = -1; k <= 1; k++)
+            {
+                for (int l = -1; l <= 1; l++)
+                {
+                    Sxx = Sxx + Ixx[i + k][j + l] * BlurGaussian::getGauss(k, l, sigma);
+                    Syy = Syy + Iyy[i + k][j + l] * BlurGaussian::getGauss(k, l, sigma);
+                    Sxy = Sxy + Ixy[i + k][j + l] * BlurGaussian::getGauss(k, l, sigma);
+                }
+            }
+
+            Sxx = Sxx / sigma_weight;
+            Sxy = Sxy / sigma_weight;
+            Syy = Syy / sigma_weight;
+
+            math::matrix<float> H(2,2);
+
+            H(0,0) = Sxx;
+            H(0,1) = Sxy;
+            H(1,0) = Sxy;
+            H(1,1) = Syy;
+
+            float detH = H(0, 0) * H(1, 1) - H(0, 1) * H(1, 0); //determinant
+            float trH = H(0, 0) + H(1, 1); //trace
+            float r = detH - k_param * pow(trH, 2);
+
+            if (r > threshold)
+            {
+                corner_candidates[i][j] = r;
+            }
+        }
+    }
+
+    bool search = true;
+
+    while(search)
+    {
+        search = false;
+        for (int i = 1;  i < width - 1; i++)
+        {
+            for (int j = 1;  j <height - 1; j++)
+            {
+                float max = corner_candidates[i][j];
+
+                for (int k = -1; k <= 1; k++)
+                {
+                    for (int l = -1; l <= 1; l++)
+                    {
+                        if (max < corner_candidates[i+k][j+l])
+                        {
+                            max = corner_candidates[i+k][j+l];
+                        }
+                    }
+                }
+
+                if (corner_candidates[i][j] == max)
+                {
+                    corner_nonmax_suppress[i][j] = corner_candidates[i][j];
+                }
+                else
+                {
+                    if (corner_candidates[i][j] > 0)
+                    {
+                        search = true;
+                    }
+
+                    corner_nonmax_suppress[i][j] = 0;
+                }
+
+            }
+        }
+        corner_candidates = corner_nonmax_suppress;
+    }
+
+    for (int i = 0; i < width; i++)
+    {
+        for (int j = 0; j < height; j++)
+        {
+            if (corner_candidates[i][j] == 0)
+            {
+                newImage->setPixel(i, j, Qt::color0);
+            }
+            else
+            {
+                newImage->setPixel(i, j, Qt::color1);
+            }
+        }
+    }
     return newImage;
 }
+
+