Merge pull request #6 from alyssaburlton/image-comparison

Image comparison

build.gradle

@@ -8,13 +8,14 @@ plugins {
 }
 
 group 'com.github.alexburlton'
-version '2.0.0'
+version '3.0.0'
 
 repositories {
     mavenCentral()
 }
 
 dependencies {
+    implementation 'com.github.romankh3:image-comparison:4.4.0'
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.8.0"
     implementation 'io.kotest:kotest-assertions-core:5.5.4'
     implementation "org.junit.jupiter:junit-jupiter-api:5.9.2"
@@ -70,7 +71,7 @@ publishing {
         mavenJava(MavenPublication) {
             groupId = 'com.github.alexburlton'
             artifactId = 'swing-test'
-            version = '2.0.0'
+            version = '3.0.0'
             from components.java
 
             pom {

src/main/kotlin/com/github/alyssaburlton/swingtest/SwingSnapshots.kt

@@ -1,5 +1,8 @@
 package com.github.alyssaburlton.swingtest
 
+import com.github.romankh3.image.comparison.ImageComparison
+import com.github.romankh3.image.comparison.model.ImageComparisonResult
+import com.github.romankh3.image.comparison.model.ImageComparisonState
 import io.kotest.assertions.fail
 import io.kotest.matchers.shouldBe
 import org.junit.jupiter.api.Assumptions
@@ -15,12 +18,10 @@ const val ENV_SCREENSHOT_OS = "screenshotOs"
 private const val DEFAULT_WIDTH = 200
 private const val DEFAULT_HEIGHT = 200
 
-fun Icon.shouldMatch(other: Icon)
-{
+fun Icon.shouldMatch(other: Icon) {
     toBufferedImage().isEqual(other.toBufferedImage()) shouldBe true
 }
-private fun Icon.toBufferedImage(): BufferedImage
-{
+private fun Icon.toBufferedImage(): BufferedImage {
     val bi = BufferedImage(iconWidth, iconHeight, BufferedImage.TYPE_INT_RGB)
     val g = bi.createGraphics()
     paintIcon(null, g, 0, 0)
@@ -31,7 +32,7 @@ private fun Icon.toBufferedImage(): BufferedImage
 fun JComponent.toBufferedImage(): BufferedImage {
     val width = getWidthForSnapshot()
     val height = getHeightForSnapshot()
-    
+
     val img = BufferedImage(width, height, BufferedImage.TYPE_4BYTE_ABGR)
     val g2 = img.createGraphics()
     paint(g2)
@@ -50,13 +51,16 @@ private fun JComponent.getHeightForSnapshot(): Int = when {
     else -> DEFAULT_HEIGHT
 }
 
-fun JComponent.shouldMatchImage(imageName: String) {
+@JvmOverloads
+fun JComponent.shouldMatchImage(imageName: String, pixelTolerance: Double = 0.01, failingPixelsThreshold: Double = 0.0) {
     verifyOs()
 
     val overwrite = System.getProperty(ENV_UPDATE_SNAPSHOT) == "true"
     val img = toBufferedImage()
 
-    val callingSite = Throwable().stackTrace[1].className
+    val stackFrames = Throwable().stackTrace.toList()
+
+    val callingSite = stackFrames.first { it.className != "com.github.alyssaburlton.swingtest.SwingSnapshotsKt" }.className
     val imgPath = "src/test/resources/__snapshots__/$callingSite"
 
     val file = File("$imgPath/$imageName.png")
@@ -70,22 +74,40 @@ fun JComponent.shouldMatchImage(imageName: String) {
         ImageIO.write(img, "png", file)
     } else {
         val savedImg = ImageIO.read(file)
-        val match = img.isEqual(savedImg)
-        if (!match) {
+        val result = ImageComparison(savedImg, img)
+            .setPixelToleranceLevel(pixelTolerance)
+            .setAllowingPercentOfDifferentPixels(failingPixelsThreshold)
+            .compareImages()
+
+        if (result.imageComparisonState != ImageComparisonState.MATCH) {
             val failedFile = File("$imgPath/$imageName.failed.png")
             ImageIO.write(img, "png", failedFile)
-            fail("Snapshot image did not match: $imgPath/$imageName.png. Run with system property -DupdateSnapshots=true to overwrite.")
+
+            val comparisonFile = File("$imgPath/$imageName.comparison.png")
+            ImageIO.write(result.result, "png", comparisonFile)
+
+            val message = "Snapshot image did not match: $imgPath/$imageName.png.\n" +
+                "A difference of ${result.differencePercentString()}% was detected\n" +
+                "See $imageName.failed.png and $imageName.comparison.png in the same directory for details.\n\n" +
+                "Run with system property -DupdateSnapshots=true to overwrite."
+
+            fail(message)
         }
     }
 }
 
+private fun ImageComparisonResult.differencePercentString(): String {
+    return "%.2f".format(100 * differencePercent)
+}
+
 private fun verifyOs() {
     val osForScreenshots = (System.getProperty(ENV_SCREENSHOT_OS) ?: "").lowercase()
 
     val os = System.getProperty("os.name").lowercase()
     if (osForScreenshots.isNotEmpty()) {
-        Assumptions.assumeTrue(os.contains(osForScreenshots),
-            "Wrong OS for screenshot tests (wanted $osForScreenshots, found $os)"
+        Assumptions.assumeTrue(
+            os.contains(osForScreenshots),
+            "Wrong OS for screenshot tests (wanted $osForScreenshots, found $os)",
         )
     }
 }

src/test/kotlin/com/github/alyssaburlton/swingtest/SwingSnapshotsTest.kt

@@ -1,5 +1,6 @@
 package com.github.alyssaburlton.swingtest
 
+import com.github.romankh3.image.comparison.ImageComparisonUtil
 import io.kotest.assertions.throwables.shouldNotThrowAny
 import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.matchers.collections.shouldContainExactly
@@ -93,25 +94,32 @@ class SwingSnapshotsTest {
 
     @Test
     fun `Should fail and write out the correct comparison file`() {
-        val comp = makeComponent("Label A")
-        comp.createImageFile("Image")
+        val lblA = resourceAsLabel("/images/label-a.png")
+        lblA.createImageFile("Image")
 
-        val otherLabel = makeComponent("Label B")
+        val lblB = resourceAsLabel("/images/label-b.png")
+        val comparisonImage = ImageComparisonUtil.readImageFromResources("images/LabelComparisonResult.png")
 
         val exception = shouldThrow<AssertionError> {
-            otherLabel.shouldMatchImage("Image")
+            lblB.shouldMatchImage("Image")
         }
 
-        exception.message shouldBe "Snapshot image did not match: $resourceLocation/Image.png. Run with system property -DupdateSnapshots=true to overwrite."
+        exception.message shouldBe "Snapshot image did not match: $resourceLocation/Image.png.\n" +
+                "A difference of 6.69% was detected\n" +
+                "See Image.failed.png and Image.comparison.png in the same directory for details.\n\n" +
+                "Run with system property -DupdateSnapshots=true to overwrite."
 
         val originalFile = File("$resourceLocation/Image.png")
         val failedFile = File("$resourceLocation/Image.failed.png")
+        val comparisonFile = File("$resourceLocation/Image.comparison.png")
 
         originalFile.shouldExist()
         failedFile.shouldExist()
+        comparisonFile.shouldExist()
 
-        ImageIO.read(originalFile).isEqual(comp.toBufferedImage()) shouldBe true
-        ImageIO.read(failedFile).isEqual(otherLabel.toBufferedImage()) shouldBe true
+        ImageIO.read(originalFile).isEqual(lblA.toBufferedImage()) shouldBe true
+        ImageIO.read(failedFile).isEqual(lblB.toBufferedImage()) shouldBe true
+        ImageIO.read(comparisonFile).isEqual(comparisonImage) shouldBe true
     }
 
     @Test
@@ -128,6 +136,28 @@ class SwingSnapshotsTest {
         File("$resourceLocation/Image.failed.png").shouldNotExist()
     }
 
+    @Test
+    fun `Should have a built-in tolerance for subtle differences`() {
+        val dartboard1 = resourceAsLabel("/images/dartboard-1.png")
+        dartboard1.createImageFile("dartboard")
+
+        val dartboard2 = resourceAsLabel("/images/dartboard-2.png")
+        shouldNotThrowAny {
+            dartboard2.shouldMatchImage("dartboard")
+        }
+    }
+
+    @Test
+    fun `Should support precise matching`() {
+        val dartboard1 = resourceAsLabel("/images/dartboard-1.png")
+        dartboard1.createImageFile("dartboard")
+
+        val dartboard2 = resourceAsLabel("/images/dartboard-2.png")
+        shouldThrow<AssertionError> {
+            dartboard2.shouldMatchImage("dartboard", pixelTolerance = 0.0)
+        }
+    }
+
     @Test
     fun `Should write a snapshot of the correct size`() {
         val labelA = JLabel("A")
@@ -197,6 +227,11 @@ class SwingSnapshotsTest {
         }
     }
 
+    private fun resourceAsLabel(resourcePath: String): JLabel {
+        val icon = ImageIcon(javaClass.getResource(resourcePath))
+        return JLabel(icon).also { it.size = Dimension(icon.iconWidth, icon.iconHeight) }
+    }
+
     private fun JComponent.createImageFile(filename: String) {
         System.setProperty(ENV_UPDATE_SNAPSHOT, "true")
         shouldMatchImage(filename)