Consider pixel order when comparing images (#227)

* Consider pixel order when comparing images

* Fix typo on README

README.md

@@ -357,7 +357,7 @@ This is the list of most useful Gradle tasks you might need divided by type of p
 
     * ``./gradlew publishToMavenLocal``: Install Shot in your local gradle repository.
     * ``./gradlew test``: Execute all the tests related to the Gradle plugin.
-    * ``./gradlew scalafmtAll`: Review the Gradle Plugin's checkstyle.
+    * ``./gradlew scalafmtAll``: Review the Gradle Plugin's checkstyle.
 
 * Consumers related tasks:
 

core/src/main/scala/com/karumi/shot/screenshots/ScreenshotsComparator.scala

@@ -15,9 +15,9 @@ class ScreenshotsComparator {
   }
 
   private def compareScreenshot(
-      screenshot: Screenshot,
-      tolerance: Double
-  ): Option[ScreenshotComparisonError] = {
+                                 screenshot: Screenshot,
+                                 tolerance: Double
+                               ): Option[ScreenshotComparisonError] = {
     val recordedScreenshotFile = new File(screenshot.recordedScreenshotPath)
     if (!recordedScreenshotFile.exists()) {
       Some(ScreenshotNotFound(screenshot))
@@ -39,23 +39,23 @@ class ScreenshotsComparator {
   }
 
   private def imagesAreDifferent(
-      screenshot: Screenshot,
-      oldScreenshot: Image,
-      newScreenshot: Image,
-      tolerance: Double
-  ) = {
+                                  screenshot: Screenshot,
+                                  oldScreenshot: Image,
+                                  newScreenshot: Image,
+                                  tolerance: Double
+                                ) = {
     if (oldScreenshot == newScreenshot) {
       false
     } else {
       val oldScreenshotPixels = oldScreenshot.pixels
       val newScreenshotPixels = newScreenshot.pixels
+
       val differentPixels =
-        oldScreenshotPixels.diff(newScreenshotPixels).length
-      val percentageOfDifferentPixels =
-        differentPixels.toDouble / oldScreenshotPixels.length.toDouble
-      val percentageOutOf100        = percentageOfDifferentPixels * 100.0
-      val imagesAreDifferent        = percentageOutOf100 >= tolerance
-      val imagesAreConsideredEquals = !imagesAreDifferent
+        oldScreenshotPixels.zip(newScreenshotPixels).filter { case (a, b) => a != b }
+      val percentageOfDifferentPixels = differentPixels.length. toDouble / oldScreenshotPixels.length.toDouble
+      val percentageOutOf100          = percentageOfDifferentPixels * 100.0
+      val imagesAreDifferent          = percentageOutOf100 >= tolerance
+      val imagesAreConsideredEquals   = !imagesAreDifferent
       if (imagesAreConsideredEquals && tolerance != Config.defaultTolerance) {
         val screenshotName = screenshot.name
         println(

core/src/test/scala/com/karumi/shot/screenshots/ScreenshotsComparatorTest.scala

@@ -0,0 +1,34 @@
+package com.karumi.shot.screenshots
+
+import com.karumi.shot.Resources
+import com.karumi.shot.domain.{Dimension, Screenshot}
+import com.karumi.shot.domain.model.ScreenshotsSuite
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should
+
+class ScreenshotsComparatorTest extends AnyFlatSpec with should.Matchers with Resources {
+
+  private val sampleImage = getClass.getClassLoader.getResource("images/sample.png").getPath
+  private val sampleImageScrambled =
+    getClass.getClassLoader.getResource("images/sample-scrambled.png").getPath
+
+  it should "not match image with same pixels but different order" in {
+    val comparator = new ScreenshotsComparator()
+    val screenshot = Screenshot("test",
+                                sampleImage,
+                                sampleImageScrambled,
+                                "SomeClass",
+                                "ShoudFail",
+                                Dimension(768, 1280),
+                                null,
+                                null,
+                                null,
+                                List(sampleImageScrambled),
+                                Dimension(768, 1280))
+    val suite: ScreenshotsSuite = List(screenshot)
+
+    val result = comparator.compare(suite, 0.01)
+
+    result.hasErrors shouldBe true
+  }
+}