Solution for issue#190

pom.xml

@@ -68,4 +68,34 @@
             </plugin>
         </plugins>
     </build>
+
+    <reporting>
+        <plugins>
+            <!-- 1. Checkstyle -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <version>3.1.2</version>
+                <reportSets>
+                    <reportSet>
+                        <reports>
+                            <report>checkstyle</report>
+                        </reports>
+                    </reportSet>
+                </reportSets>
+            </plugin>
+            <!-- 2. PMD -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-pmd-plugin</artifactId>
+                <version>3.16.0</version>
+                <configuration>
+                    <rulesets>
+                        <ruleset>/rulesets/java/quickstart.xml</ruleset>
+                    </rulesets>
+                    <printFailingErrors>true</printFailingErrors>
+                </configuration>
+            </plugin>
+        </plugins>
+    </reporting>
 </project>

src/main/java/com/github/romankh3/image/comparison/ImageComparisonUtil.java

@@ -16,11 +16,18 @@
 import javax.imageio.ImageIO;
 import javax.swing.ImageIcon;
 
+
+
+
 /**
  * Tools for the {@link ImageComparison} object.
  */
 public final class ImageComparisonUtil {
 
+    public static int OFFSET = 0xff;
+    public static int EIGHT = 8;
+    public static int TENSIX = 8;
+
     /**
      * Make a copy of the {@link BufferedImage} object.
      *
@@ -142,11 +149,13 @@ public static float getDifferencePercent(BufferedImage img1, BufferedImage img2)
         long diff = 0;
         for (int y = 0; y < height; y++) {
             for (int x = 0; x < width; x++) {
-                diff += pixelDiff(img1.getRGB(x, y), img2.getRGB(x, y));
+                if(isDiffPixel(img1.getRGB(x, y), img2.getRGB(x, y))) {
+                    diff += 1;
+                }
             }
         }
-        long maxDiff = 3L * 255 * width * height;
-
+        //CS304 Issue link: https://github.com/romankh3/image-comparison/issues/190
+        long maxDiff = (long) width * height;
         return (float) (100.0 * diff / maxDiff);
     }
 
@@ -166,4 +175,22 @@ public static int pixelDiff(int rgb1, int rgb2) {
         int b2 = rgb2 & 0xff;
         return Math.abs(r1 - r2) + Math.abs(g1 - g2) + Math.abs(b1 - b2);
     }
+
+    /**
+     * Compare two pixels.
+     *
+     * @param rgb1 the first rgb
+     * @param rgb2 the second rgb
+     * @return true If they are the same RGB pixel.
+     */
+    //CS304 Issue link: https://github.com/romankh3/image-comparison/issues/190
+    public static boolean isDiffPixel(final int rgb1, final int rgb2) {
+        int r1 = (rgb1 >> TENSIX) & OFFSET;
+        int g1 = (rgb1 >> EIGHT) & OFFSET;
+        int b1 = rgb1 & OFFSET;
+        int r2 = (rgb2 >> TENSIX) & OFFSET;
+        int g2 = (rgb2 >> EIGHT) & OFFSET;
+        int b2 = rgb2 & OFFSET;
+        return Math.abs(r1 - r2) + Math.abs(g1 - g2) + Math.abs(b1 - b2) != 0;
+    }
 }

src/test/java/com/github/romankh3/image/comparison/ImageComparisonUnitTest.java

@@ -24,6 +24,44 @@
 @DisplayName("Unit-level testing for {@link ImageComparison} object.")
 public class ImageComparisonUnitTest {
 
+    //CS304 (manually written) Issue link: https://github.com/romankh3/image-comparison/issues/190
+    @DisplayName("For issue#190, test the Percentage of Different Pixels of different images")
+    @Test
+    public void testDifferencePercent1() {
+        //given
+        BufferedImage expectedResultImage = readImageFromResources("result.png");
+        File file = new File("build/test-images/result.png");
+        float actualPercent = (float) (100.0 * 695 / (985 * 701));
+        //when
+        ImageComparison imageComparison = new ImageComparison("expected.png", "actual.png");
+        ImageComparisonResult imageComparisonResult = imageComparison.compareImages().writeResultTo(file);
+
+        //then
+        assertNotNull(imageComparison.getActual());
+        assertNotNull(imageComparison.getExpected());
+        assertEquals(MISMATCH, imageComparisonResult.getImageComparisonState());
+        assertEquals(actualPercent, imageComparisonResult.getDifferencePercent());
+    }
+
+    //CS304 (manually written) Issue link: https://github.com/romankh3/image-comparison/issues/190
+    @DisplayName("For issue#190, test the Percentage of Different Pixels of the same images")
+    @Test
+    public void testDifferencePercent2() {
+        //given
+        BufferedImage expectedResultImage = readImageFromResources("result.png");
+        File file = new File("build/test-images/result.png");
+        float actualPercent = 0.0f;
+        //when
+        ImageComparison imageComparison = new ImageComparison("actual.png", "actual.png");
+        ImageComparisonResult imageComparisonResult = imageComparison.compareImages().writeResultTo(file);
+
+        //then
+        assertNotNull(imageComparison.getActual());
+        assertNotNull(imageComparison.getExpected());
+        assertEquals(MATCH, imageComparisonResult.getImageComparisonState());
+        assertEquals(actualPercent, imageComparisonResult.getDifferencePercent());
+    }
+
     @DisplayName("The most important test. Shown, that the changes in algorithm, "
             + "don't break the main behaviour and result as expected")
     @Test