diff --git a/ImGuiVisitor.cpp b/ImGuiVisitor.cpp
index f4f5269..fc6eebb 100644
--- a/ImGuiVisitor.cpp
+++ b/ImGuiVisitor.cpp
@@ -206,7 +206,7 @@ void ImGuiVisitor::visit(ImageProcessingShader &n)
     if (ImGuiToolkit::ButtonIcon(1, 7)) n.filterid = 0;
     ImGui::SameLine(0, 10);
     ImGui::SetNextItemWidth(RIGHT_ALIGN);
-    ImGui::Combo("Filter", &n.filterid, "None\0Blur\0Sharpen\0Edge\0Emboss\0Erode 3x3\0Erode 5x5\0Erode 7x7\0Dilate 3x3\0Dilate 5x5\0Dilate 7x7\0");
+    ImGui::Combo("Filter", &n.filterid, "None\0Blur\0Sharpen\0Edge\0Emboss\0Denoising\0Erode 3x3\0Erode 5x5\0Erode 7x7\0Dilate 3x3\0Dilate 5x5\0Dilate 7x7\0");
 
     if (ImGuiToolkit::ButtonIcon(7, 1)) n.invert = 0;
     ImGui::SameLine(0, 10);
diff --git a/ImageProcessingShader.h b/ImageProcessingShader.h
index 9e1ddf0..efcc038 100644
--- a/ImageProcessingShader.h
+++ b/ImageProcessingShader.h
@@ -38,7 +38,8 @@ public:
     // filter identifyer
     // [0] No filter
     // [1 4] 4 x kernel operations;  Blur, Sharpen, Edge, Emboss
-    // [5 10] 6 x convolutions: erosion 3, 5, 7, dilation 3, 5, 7
+    // [5] 1 x convolution opening (denoising)
+    // [6 11] 6 x convolutions: erosion 3x3, 5x5, 7x7, dilation 3x3, 5x5, 7x7
     int filterid;
 
 };
diff --git a/rsc/shaders/imageprocessing.fs b/rsc/shaders/imageprocessing.fs
index 67b2287..f2dbe3b 100644
--- a/rsc/shaders/imageprocessing.fs
+++ b/rsc/shaders/imageprocessing.fs
@@ -79,7 +79,7 @@ vec3 erosion(int N, vec2 filter_step)
     minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, 0.0) * filter_step ).rgb, minValue);
     minValue = min(texture(iChannel0, vertexUV + vec2 (1.0, 0.0) * filter_step ).rgb, minValue);
     minValue = min(texture(iChannel0, vertexUV + vec2 (0.0, 1.0) * filter_step ).rgb, minValue);
-    if (N == 3)
+    if (N < 1)
         return minValue;
     minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, -2.0) * filter_step ).rgb, minValue);
     minValue = min(texture(iChannel0, vertexUV + vec2 (0.0,-2.0) * filter_step ).rgb, minValue);
@@ -97,7 +97,7 @@ vec3 erosion(int N, vec2 filter_step)
     minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, -1.0) * filter_step ).rgb, minValue);
     minValue = min(texture(iChannel0, vertexUV + vec2 (-2.0, 0.0) * filter_step ).rgb, minValue);
     minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, 0.0) * filter_step ).rgb, minValue);
-    if (N == 5)
+    if (N < 2)
         return minValue;
     minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, -3.0) * filter_step ).rgb, minValue);
     minValue = min(texture(iChannel0, vertexUV + vec2 (0.0,-3.0) * filter_step ).rgb, minValue);
@@ -128,7 +128,7 @@ vec3 dilation(int N, vec2 filter_step)
     maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, 0.0) * filter_step ).rgb, maxValue);
     maxValue = max(texture(iChannel0, vertexUV + vec2 (1.0, 0.0) * filter_step ).rgb, maxValue);
     maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0, 1.0) * filter_step ).rgb, maxValue);
-    if (N == 3)
+    if (N < 1)
         return maxValue;
     maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, -2.0) * filter_step ).rgb, maxValue);
     maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0,-2.0) * filter_step ).rgb, maxValue);
@@ -146,7 +146,7 @@ vec3 dilation(int N, vec2 filter_step)
     maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, -1.0) * filter_step ).rgb, maxValue);
     maxValue = max(texture(iChannel0, vertexUV + vec2 (-2.0, 0.0) * filter_step ).rgb, maxValue);
     maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, 0.0) * filter_step ).rgb, maxValue);
-    if (N == 5)
+    if (N < 2)
         return maxValue;
     maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, -3.0) * filter_step ).rgb, maxValue);
     maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0,-3.0) * filter_step ).rgb, maxValue);
@@ -168,6 +168,45 @@ vec3 dilation(int N, vec2 filter_step)
     return maxValue;
 }
 
+
+vec3 opening(vec2 filter_step)
+{
+    // 1) erosion
+    vec3 minValue1 = vec3(1.0);
+    minValue1 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, vertexUV + vec2 (0.0, 1.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, vertexUV + vec2 (0.0, 2.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, vertexUV + vec2 (1.0, 1.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, vertexUV + vec2 (1.0, -1.0) * filter_step ).rgb, minValue1);
+    vec3 minValue2 = vec3(1.0);
+    minValue2 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, vertexUV + vec2 (-1.0, 0.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, vertexUV + vec2 (-2.0, 0.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, vertexUV + vec2 (1.0, -1.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, vertexUV + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue2);
+    vec3 minValue3 = vec3(1.0);
+    minValue3 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, vertexUV + vec2 (0.0, -1.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, vertexUV + vec2 (0.0, -2.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, vertexUV + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, vertexUV + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue3);
+    vec3 minValue4 = vec3(1.0);
+    minValue4 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, vertexUV + vec2 (1.0, 0.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, vertexUV + vec2 (2.0, 0.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, vertexUV + vec2 (1.0, 1.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, vertexUV + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue4);
+
+    // 2) dilation
+    vec3 maxValue = vec3(0.0);
+    maxValue = max(minValue1, maxValue);
+    maxValue = max(minValue2, maxValue);
+    maxValue = max(minValue3, maxValue);
+    maxValue = max(minValue4, maxValue);
+
+    return maxValue;
+}
+
 vec3 convolution(mat3 kernel, vec2 filter_step)
 {
     int i = 0, j = 0;
@@ -184,14 +223,16 @@ vec3 apply_filter() {
 
     vec2 filter_step = 1.f / textureSize(iChannel0, 0);
 
-    if (filterid < 1 || filterid > 10)
+    if (filterid < 1 || filterid > 11)
         return texture(iChannel0, vertexUV).rgb;
     else if (filterid < 5)
         return convolution( KERNEL[filterid], filter_step);
-    else if (filterid < 8)
-        return erosion( 3 + (filterid -5) * 2, filter_step);
+    else if (filterid < 6)
+        return opening(filter_step);
+    else if (filterid < 9)
+        return erosion( filterid - 6 , filter_step);
     else
-        return dilation( 3 + (filterid -8) * 2, filter_step);
+        return dilation( filterid - 9, filter_step);
 }
 
 /*