Revert "Delete FilterDifferenceTest.java"

This reverts commit eebfd3f.

src/test/java/com/marginallyclever/makelangelo/makeart/imagefilter/FilterDifferenceTest.java

@@ -0,0 +1,36 @@
+package com.marginallyclever.makelangelo.makeart.imagefilter;
+
+import com.marginallyclever.makelangelo.makeart.TransformedImage;
+import org.junit.jupiter.api.Test;
+
+import javax.imageio.ImageIO;
+import java.io.FileInputStream;
+import java.io.IOException;
+
+public class FilterDifferenceTest {
+    @Test
+    public void test() throws IOException {
+        TransformedImage src = new TransformedImage( ImageIO.read(new FileInputStream("src/test/resources/chicken.png")) );
+        Filter_GaussianBlur a = new Filter_GaussianBlur(src,2);
+        TransformedImage a2 = a.filter();
+        ImageIO.write(a2.getSourceImage(), "jpg", new java.io.File("src/test/resources/chicken-a.jpg"));
+
+        Filter_GaussianBlur b = new Filter_GaussianBlur(src,4);
+        TransformedImage b2 = b.filter();
+        ImageIO.write(b2.getSourceImage(), "jpg", new java.io.File("src/test/resources/chicken-b.jpg"));
+
+        Filter_Scale scale = new Filter_Scale(b2,0.85);
+        TransformedImage afterScale = scale.filter();
+        ImageIO.write(afterScale.getSourceImage(), "jpg", new java.io.File("src/test/resources/chicken-c.jpg"));
+
+        Filter_Difference diff = new Filter_Difference(a2,afterScale);
+        TransformedImage afterDiff = diff.filter();
+        ImageIO.write(afterDiff.getSourceImage(), "jpg", new java.io.File("src/test/resources/chicken-d.jpg"));
+
+        Filter_Threshold threshold = new Filter_Threshold(afterDiff,8);
+        TransformedImage afterThreshold = threshold.filter();
+
+        ImageIO.write(afterThreshold.getSourceImage(), "jpg", new java.io.File("src/test/resources/chicken-difference.jpg"));
+    }
+
+}