diff --git a/services/surfaceflinger/Effects/Daltonizer.cpp b/services/surfaceflinger/Effects/Daltonizer.cpp
index a7090c5..65f2605 100644
--- a/services/surfaceflinger/Effects/Daltonizer.cpp
+++ b/services/surfaceflinger/Effects/Daltonizer.cpp
@@ -37,6 +37,18 @@
     }
 }
 
+void Daltonizer::setLevel(int32_t level) {
+    if (level < 0 || level > 10) {
+        return;
+    }
+
+    float newLevel = level / 10.0f;
+    if (std::fabs(mLevel - newLevel) > 0.09f) {
+        mDirty = true;
+    }
+    mLevel = newLevel;
+}
+
 const mat4& Daltonizer::operator()() {
     if (mDirty) {
         mDirty = false;
@@ -117,25 +129,24 @@
     // a color blind user and "spread" this error onto the healthy cones.
     // The matrices below perform this last step and have been chosen arbitrarily.
 
-    // The amount of correction can be adjusted here.
-
+    // Scale 0 represents no change (mColorTransform is identical matrix).
     // error spread for protanopia
-    const mat4 errp(    1.0, 0.7, 0.7, 0,
-                        0.0, 1.0, 0.0, 0,
-                        0.0, 0.0, 1.0, 0,
-                          0,   0,   0, 1);
+    const mat4 errp(1.0, mLevel, mLevel, 0.0,
+                    0.0,    1.0,    0.0, 0.0,
+                    0.0,    0.0,    1.0, 0.0,
+                    0.0,    0.0,    0.0, 1.0);
 
     // error spread for deuteranopia
-    const mat4 errd(    1.0, 0.0, 0.0, 0,
-                        0.7, 1.0, 0.7, 0,
-                        0.0, 0.0, 1.0, 0,
-                          0,   0,   0, 1);
+    const mat4 errd(   1.0, 0.0,    0.0, 0.0,
+                    mLevel, 1.0, mLevel, 0.0,
+                       0.0, 0.0,    1.0, 0.0,
+                       0.0, 0.0,    0.0, 1.0);
 
     // error spread for tritanopia
-    const mat4 errt(    1.0, 0.0, 0.0, 0,
-                        0.0, 1.0, 0.0, 0,
-                        0.7, 0.7, 1.0, 0,
-                          0,   0,   0, 1);
+    const mat4 errt(   1.0,    0.0, 0.0, 0.0,
+                       0.0,    1.0, 0.0, 0.0,
+                    mLevel, mLevel, 1.0, 0.0,
+                       0.0,    0.0, 0.0, 1.0);
 
     // And the magic happens here...
     // We construct the matrix that will perform the whole correction.
diff --git a/services/surfaceflinger/Effects/Daltonizer.h b/services/surfaceflinger/Effects/Daltonizer.h
index 2fb60e9..f5eaae7 100644
--- a/services/surfaceflinger/Effects/Daltonizer.h
+++ b/services/surfaceflinger/Effects/Daltonizer.h
@@ -21,6 +21,9 @@
 
 namespace android {
 
+// Forward declare test class
+class DaltonizerTest;
+
 enum class ColorBlindnessType {
     None,               // Disables the Daltonizer
     Protanomaly,        // L (red) cone deficient
@@ -37,10 +40,15 @@
 public:
     void setType(ColorBlindnessType type);
     void setMode(ColorBlindnessMode mode);
+    // sets level for correction saturation, [0-10].
+    void setLevel(int32_t level);
 
     // returns the color transform to apply in the shader
     const mat4& operator()();
 
+    // For testing.
+    friend class DaltonizerTest;
+
 private:
     void update();
 
@@ -48,6 +56,8 @@
     ColorBlindnessMode mMode = ColorBlindnessMode::Simulation;
     bool mDirty = true;
     mat4 mColorTransform;
+    // level of error spreading, [0.0-1.0].
+    float mLevel = 0.7f;
 };
 
 } /* namespace android */
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index c237a7d..70b9e43 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -7154,6 +7154,7 @@
                 Mutex::Autolock _l(mStateLock);
                 // daltonize
                 n = data.readInt32();
+                mDaltonizer.setLevel(data.readInt32());
                 switch (n % 10) {
                     case 1:
                         mDaltonizer.setType(ColorBlindnessType::Protanomaly);
diff --git a/services/surfaceflinger/tests/unittests/Android.bp b/services/surfaceflinger/tests/unittests/Android.bp
index 0c13db3..5145e11 100644
--- a/services/surfaceflinger/tests/unittests/Android.bp
+++ b/services/surfaceflinger/tests/unittests/Android.bp
@@ -66,6 +66,7 @@
         "BackgroundExecutorTest.cpp",
         "CommitTest.cpp",
         "CompositionTest.cpp",
+        "DaltonizerTest.cpp",
         "DisplayIdGeneratorTest.cpp",
         "DisplayTransactionTest.cpp",
         "DisplayDevice_GetBestColorModeTest.cpp",
diff --git a/services/surfaceflinger/tests/unittests/DaltonizerTest.cpp b/services/surfaceflinger/tests/unittests/DaltonizerTest.cpp
new file mode 100644
index 0000000..9f632a1
--- /dev/null
+++ b/services/surfaceflinger/tests/unittests/DaltonizerTest.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+#include <math/mat4.h>
+#include <cmath>
+#include "Effects/Daltonizer.h"
+
+namespace android {
+
+class DaltonizerTest {
+private:
+    Daltonizer& mDaltonizer;
+
+public:
+    DaltonizerTest(Daltonizer& daltonizer) : mDaltonizer(daltonizer) {}
+
+    bool isDirty() const { return mDaltonizer.mDirty; }
+
+    float getLevel() const { return mDaltonizer.mLevel; }
+
+    ColorBlindnessType getType() const { return mDaltonizer.mType; }
+};
+
+constexpr float TOLERANCE = 0.01f;
+
+static bool isIdentityMatrix(mat4& matrix) {
+    for (size_t i = 0; i < 4; ++i) {
+        for (size_t j = 0; j < 4; ++j) {
+            if (i == j) {
+                // Check diagonal elements
+                if (std::fabs(matrix[i][j] - 1.0f) > TOLERANCE) {
+                    return false;
+                }
+            } else {
+                // Check off-diagonal elements
+                if (std::fabs(matrix[i][j]) > TOLERANCE) {
+                    return false;
+                }
+            }
+        }
+    }
+    return true;
+}
+
+// Test Suite Name : DaltonizerTest, Test name: ConstructionDefaultValues
+TEST(DaltonizerTest, ConstructionDefaultValues) {
+    Daltonizer daltonizer;
+    DaltonizerTest test(daltonizer);
+
+    EXPECT_EQ(test.getLevel(), 0.7f);
+    ASSERT_TRUE(test.isDirty());
+    EXPECT_EQ(test.getType(), ColorBlindnessType::None);
+    mat4 matrix = daltonizer();
+    ASSERT_TRUE(isIdentityMatrix(matrix));
+}
+
+TEST(DaltonizerTest, NotDirtyAfterColorMatrixReturned) {
+    Daltonizer daltonizer;
+
+    mat4 matrix = daltonizer();
+    DaltonizerTest test(daltonizer);
+
+    ASSERT_FALSE(test.isDirty());
+    ASSERT_TRUE(isIdentityMatrix(matrix));
+}
+
+TEST(DaltonizerTest, LevelOutOfRangeTooLowIgnored) {
+    Daltonizer daltonizer;
+    // Get matrix to reset isDirty == false.
+    mat4 matrix = daltonizer();
+
+    daltonizer.setLevel(-1);
+    DaltonizerTest test(daltonizer);
+
+    EXPECT_EQ(test.getLevel(), 0.7f);
+    ASSERT_FALSE(test.isDirty());
+}
+
+TEST(DaltonizerTest, LevelOutOfRangeTooHighIgnored) {
+    Daltonizer daltonizer;
+    // Get matrix to reset isDirty == false.
+    mat4 matrix = daltonizer();
+
+    daltonizer.setLevel(11);
+    DaltonizerTest test(daltonizer);
+
+    EXPECT_EQ(test.getLevel(), 0.7f);
+    ASSERT_FALSE(test.isDirty());
+}
+
+TEST(DaltonizerTest, ColorCorrectionMatrixNonIdentical) {
+    Daltonizer daltonizer;
+    daltonizer.setType(ColorBlindnessType::Protanomaly);
+    daltonizer.setMode(ColorBlindnessMode::Correction);
+
+    mat4 matrix = daltonizer();
+
+    ASSERT_FALSE(isIdentityMatrix(matrix));
+}
+
+TEST(DaltonizerTest, LevelZeroColorMatrixEqIdentityMatrix) {
+    Daltonizer daltonizer;
+    daltonizer.setType(ColorBlindnessType::Protanomaly);
+    daltonizer.setMode(ColorBlindnessMode::Correction);
+    daltonizer.setLevel(0);
+
+    mat4 matrix = daltonizer();
+
+    ASSERT_TRUE(isIdentityMatrix(matrix));
+}
+
+} /* namespace android */