diff --git a/libs/pigment/compositeops/KoCompositeOpAlphaDarken.h b/libs/pigment/compositeops/KoCompositeOpAlphaDarken.h
index e51e1a6..c05668e 100644
--- a/libs/pigment/compositeops/KoCompositeOpAlphaDarken.h
+++ b/libs/pigment/compositeops/KoCompositeOpAlphaDarken.h
@@ -91,7 +91,24 @@ public:
                     channels_type fullFlowAlpha;
                     channels_type averageOpacity = scale<channels_type>(*params.lastOpacity);
 
+                    /**
+                     * Here we calculate fullFlowAlpha, which shuold strive either to
+                     * averageOpacity or opacity (whichever is the greater) or just keep old dstAlpha
+                     * value, if both opacity values are not bit enough
+                     */
                     if (averageOpacity > opacity) {
+                        /**
+                         * This crypty code is basically an optimized version of the folowing:
+                         * fullFlowAlpha = averageOpacity *
+                         *                     unionShapeOpacity(srcAlpha / averageOpacity,
+                         *                                       dstAlpha / averageOpacity);
+                         *
+                         * The main idea is: fullFlowAlpha should be as near to averageOpacity as
+                         * maximum of srcAlpha and dstAlpha and a bit more. So that in consequent
+                         * applications of the blending operation alpha channel would aim to
+                         * averageOpacity.
+                         */
+
                         channels_type reverseBlend = KoColorSpaceMaths<channels_type>::divide(dstAlpha, averageOpacity);
                         fullFlowAlpha = averageOpacity > dstAlpha ? lerp(srcAlpha, averageOpacity, reverseBlend) : dstAlpha;
                     } else {
@@ -103,8 +120,6 @@ public:
                     } else {
                         channels_type zeroFlowAlpha = dstAlpha;
                         dstAlpha = lerp(zeroFlowAlpha, fullFlowAlpha, flow);
-
-
                     }
 
                     dst[alpha_pos] = dstAlpha;