Add difference percentages to CompareResult

src/main/java/de/redsix/pdfcompare/CompareResult.java

@@ -2,6 +2,7 @@
 
 import java.io.OutputStream;
 import java.util.Collection;
+import java.util.Map;
 
 public interface CompareResult {
 
@@ -99,4 +100,11 @@ public interface CompareResult {
      * @return collection of page numbers, that have a difference
      */
     Collection<Integer> getPagesWithDifferences();
+
+    /**
+     * Gives a map of the difference percentages per page.
+     * 
+     * @return difference percentages mapped to the page index.
+     */
+    Map<Integer, Double> getPageDiffsInPercent();
 }

src/main/java/de/redsix/pdfcompare/CompareResultImpl.java

@@ -47,6 +47,7 @@ public class CompareResultImpl implements ResultCollector, CompareResult {
     private boolean expectedOnly;
     private boolean actualOnly;
     private final Collection<PageArea> diffAreas = new ArrayList<>();
+    private final Map<Integer, Double> diffPercentages = new TreeMap<>();
     private int pages = 0;
 
     @Override
@@ -131,10 +132,14 @@ public synchronized void addPage(final PageDiffCalculator diffCalculator, final
             isEqual = false;
             diffAreas.add(diffCalculator.getDiffArea());
             diffImages.put(pageIndex, diffImage);
+            diffPercentages.put(pageIndex, diffCalculator.getDifferenceInPercent());
             pages++;
-        } else if (environment.addEqualPagesToResult()) {
-            diffImages.put(pageIndex, diffImage);
-            pages++;
+        } else {
+            diffPercentages.put(pageIndex, 0.0);
+            if (environment.addEqualPagesToResult()) {
+                diffImages.put(pageIndex, diffImage);
+                pages++;
+            }
         }
     }
 
@@ -193,6 +198,11 @@ public Collection<Integer> getPagesWithDifferences() {
         return diffAreas.stream().map(a -> a.page).collect(Collectors.toList());
     }
 
+    @Override
+    public Map<Integer, Double> getPageDiffsInPercent() {
+        return diffPercentages;
+    }
+
     public void expectedOnly() {
         this.expectedOnly = true;
     }

src/main/java/de/redsix/pdfcompare/PageDiffCalculator.java

@@ -50,6 +50,14 @@ public boolean differencesFoundInExclusion() {
         return diffsFoundInExclusion > 0;
     }
 
+    public double getDifferenceInPercent() {
+        if (totalPixels == 0) {
+            return diffsFound > 0 ? 100.0 : 0.0;
+        } else {
+            return (double)diffsFound / (double)totalPixels * 100.0;
+        }
+    }
+
     @Override
     public boolean equals(final Object o) {
         if (this == o) {

src/test/java/de/redsix/pdfcompare/CompareResultImplTest.java

@@ -1,12 +1,14 @@
 package de.redsix.pdfcompare;
 
+import static org.hamcrest.collection.IsMapContaining.hasEntry;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.is;
 
 import de.redsix.pdfcompare.env.SimpleEnvironment;
 import org.junit.jupiter.api.Test;
 
 import java.awt.image.BufferedImage;
+import java.util.Map;
 
 class CompareResultImplTest {
 
@@ -35,4 +37,22 @@ public void addEqualPagesAreNotStored() {
         assertThat(compareResult.getNumberOfPages(), is(1));
         assertThat(compareResult.diffImages.size(), is(1));
     }
+
+    @Test
+    public void mapsDiffPercentagesCorrectly() {
+        CompareResultImpl compareResult = new CompareResultImpl();
+        compareResult.setEnvironment(new SimpleEnvironment());
+        ImageWithDimension image = new ImageWithDimension(new BufferedImage(1, 1, BufferedImage.TYPE_BYTE_BINARY), 0.0f, 0.0f);
+
+        PageDiffCalculator pageWithDiff = new PageDiffCalculator(5, 0);
+        pageWithDiff.diffFound();
+        PageDiffCalculator pageWithoutDiff = new PageDiffCalculator(10, 0);
+
+        compareResult.addPage(pageWithDiff, 1, image, image, image);
+        compareResult.addPage(pageWithoutDiff, 2, image, image, image);
+
+        Map<Integer, Double> result = compareResult.getPageDiffsInPercent();
+        assertThat(result, hasEntry(1, 20.0));
+        assertThat(result, hasEntry(2, 0.0));
+    }
 }

src/test/java/de/redsix/pdfcompare/PageDiffCalculatorTest.java

@@ -1,5 +1,6 @@
 package de.redsix.pdfcompare;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -62,4 +63,31 @@ public void diffAbovePercentageAsFractionIsReported() {
         diffCalculator.diffFound();
         assertTrue(diffCalculator.differencesFound());
     }
+
+    @Test
+    public void zeroTotalPixelsWithDiffFoundReportsHundredPercentDifference() {
+        final PageDiffCalculator diffCalculator = new PageDiffCalculator(0, 0);
+        diffCalculator.diffFound();
+        assertEquals(100.0, diffCalculator.getDifferenceInPercent());
+    }
+
+    @Test
+    public void zeroTotalPixelsWithNoDiffFoundReportsZeroPercentDifference() {
+        final PageDiffCalculator diffCalculator = new PageDiffCalculator(0, 0);
+        assertEquals(0.0, diffCalculator.getDifferenceInPercent());
+    }
+
+    @Test
+    public void diffsFoundReportsCorrectPercentage() {
+        final PageDiffCalculator diffCalculator = new PageDiffCalculator(10, 0);
+        diffCalculator.diffFound();
+        diffCalculator.diffFound();
+        assertEquals(20.0, diffCalculator.getDifferenceInPercent());
+    }
+
+    @Test
+    public void noDiffsFoundReportsCorrectPercentage() {
+        final PageDiffCalculator diffCalculator = new PageDiffCalculator(6, 0);
+        assertEquals(0.0, diffCalculator.getDifferenceInPercent());
+    }
 }