JDK-8209968: Fix off by one error in image scale calculation

modules/javafx.graphics/src/main/java/com/sun/javafx/iio/common/ImageTools.java

@@ -662,13 +662,13 @@ public static int[] computeDimensions(int sourceWidth, int sourceHeight,
             if (preserveAspectRatio) {
                 // compute the final dimensions
                 if (finalWidth == 0) {
-                    finalWidth = (int) ((float) sourceWidth * finalHeight / sourceHeight);
+                    finalWidth = Math.round((float) sourceWidth * finalHeight / sourceHeight);
                 } else if (finalHeight == 0) {
-                    finalHeight = (int) ((float) sourceHeight * finalWidth / sourceWidth);
+                    finalHeight = Math.round((float) sourceHeight * finalWidth / sourceWidth);
                 } else {
                     float scale = Math.min((float) finalWidth / sourceWidth, (float) finalHeight / sourceHeight);
-                    finalWidth = (int) (sourceWidth * scale);
-                    finalHeight = (int) (sourceHeight * scale);
+                    finalWidth = Math.round(sourceWidth * scale);
+                    finalHeight = Math.round(sourceHeight * scale);
                 }
             } else {
                 // set final dimensions to default if zero

modules/javafx.graphics/src/test/java/test/com/sun/javafx/iio/common/ImageToolsTest.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package test.com.sun.javafx.iio.common;
+
+import com.sun.javafx.iio.common.ImageTools;
+import static org.junit.Assert.*;
+import org.junit.Test;
+
+import java.util.Random;
+
+public class ImageToolsTest {
+    private static final int RANDOM_SEED = 1;  // A random seed
+    private static final int MIN_SIZE = 1;  // Smallest dimension to generate
+    private static final int MAX_SIZE = 1000;  // Largest dimension to generate
+    private static final int RANGE = MAX_SIZE - MIN_SIZE;  // Generate dimension range
+    private static final int RANDOM_COUNT = 1000;  // Number of random source and target dimensions to generate and verify
+
+    private final Random rnd = new Random(RANDOM_SEED);
+
+    @Test
+    public void testIfComputeDimensionsReturnsValuesInCorrectRangeWhenAspectRatioIsPreserved() {
+        // Test a few specific corner cases:
+        assertComputeDimensions(1000, 1500, 108, 108);
+        assertComputeDimensions(800, 1200, 108, 108);
+        assertComputeDimensions(1400, 2100, 108, 108);
+        assertComputeDimensions(2000, 3000, 108, 108);
+        assertComputeDimensions(98, 97, 40, 50);
+        assertComputeDimensions(98, 97, 40, 0);
+        assertComputeDimensions(98, 97, 0, 50);
+        assertComputeDimensions(98, 97, 0, 0);
+        assertComputeDimensions(98, 97, -1, -1);
+        assertComputeDimensions(98, 97, 98, 97);
+        assertComputeDimensions(98, 6, 3, 3);
+
+        // Test a few random values:
+        for (int i = 0; i < RANDOM_COUNT; i++) {
+            int sw = rnd.nextInt(RANGE) + MIN_SIZE;
+            int sh = rnd.nextInt(RANGE) + MIN_SIZE;
+            int tw = rnd.nextInt(RANGE) + MIN_SIZE;
+            int th = rnd.nextInt(RANGE) + MIN_SIZE;
+
+            assertComputeDimensions(sw, sh, tw, th);
+        }
+    }
+
+    @Test
+    public void testIfComputeDimensionsReturnsValuesInCorrectRangeWhenAspectRatioIsNotPreserved() {
+        assertArrayEquals(new int[] {10, 15}, ImageTools.computeDimensions(100, 101, 10, 15, false));
+        assertArrayEquals(new int[] {100, 15}, ImageTools.computeDimensions(100, 101, 0, 15, false));
+        assertArrayEquals(new int[] {100, 101}, ImageTools.computeDimensions(100, 101, 0, 0, false));
+        assertArrayEquals(new int[] {10, 101}, ImageTools.computeDimensions(100, 101, 10, 0, false));
+        assertArrayEquals(new int[] {100, 101}, ImageTools.computeDimensions(100, 101, -1, 0, false));
+        assertArrayEquals(new int[] {100, 101}, ImageTools.computeDimensions(100, 101, -1, -1, false));
+        assertArrayEquals(new int[] {100, 101}, ImageTools.computeDimensions(100, 101, 0, -1, false));
+    }
+
+    private static void assertComputeDimensions(int sw, int sh, int tw, int th) {
+        int[] result = ImageTools.computeDimensions(sw, sh, tw, th, true);
+
+        int x = result[0];
+        int y = result[1];
+        double originalAspect = (double)sw / sh;
+
+        String msg = String.format("src: %dx%d, target: %dx%d, result: %dx%d", sw, sh, tw, th, x, y);
+
+        // When any target dimension is 0 or negative, it defaults to the source dimension size
+        tw = tw <= 0 ? sw : tw;
+        th = th <= 0 ? sh : th;
+
+        // Result should always return dimensions in the range of 0 < x <= size,
+        // and one dimension must be equal to one of the target dimensions.
+        assertTrue(msg, x <= tw);
+        assertTrue(msg, y <= th);
+        assertTrue(msg, x > 0);
+        assertTrue(msg, y > 0);
+        assertTrue(msg, x == tw || y == th);
+
+        // Check the non-maxed dimension to see if it is within 1 pixel of the expected value
+        // when calculated with the original aspect ratio:
+        if (x != tw) {
+            assertTrue(msg, x == Math.floor(th * originalAspect) || x == Math.ceil(th * originalAspect));
+        }
+        if (y != th) {
+            assertTrue(msg, y == Math.floor(tw / originalAspect) || y == Math.ceil(tw / originalAspect));
+        }
+    }
+}