8258986: getColor throws IOOBE when PixelReader reads the same pixel …

…twice

modules/javafx.graphics/src/main/java/com/sun/prism/Image.java

@@ -650,9 +650,9 @@ private Accessor<?> getPixelAccessor() {
                                                   (IntBuffer) pixelBuffer);
                     break;
             }
-        }
-        if (pixelaccessor != null && pixelScale != 1.0f) {
-            pixelaccessor = new ScaledAccessor<>(pixelaccessor, pixelScale);
+            if (pixelScale != 1.0f) {
+                pixelaccessor = new ScaledAccessor<>(pixelaccessor, pixelScale);
+            }
         }
         return pixelaccessor;
     }

modules/javafx.graphics/src/test/java/test/com/sun/javafx/iio/ImageHiDPITest.java

@@ -0,0 +1,157 @@
+/*
+ * Copyright (c) 2021, 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;
+
+import com.sun.javafx.iio.ImageFrame;
+import com.sun.javafx.iio.ImageStorage;
+import com.sun.javafx.iio.ImageStorageException;
+import com.sun.prism.Image;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * Test multiple calls to getPixel with both a normal image
+ * and a Hi-DPI "@2x" image.
+ *
+ * @test
+ * @bug 8258986
+ */
+public class ImageHiDPITest {
+    private static final String IMAGE_NAME = "checker.png";
+
+    private String imagePath;
+
+    @Before
+    public void setup() {
+        imagePath = this.getClass().getResource(IMAGE_NAME).toExternalForm();
+        assertNotNull(imagePath);
+    }
+
+    private ImageFrame loadImage(String path, float pixelScale) {
+        try {
+            ImageFrame[] imageFrames =
+                    ImageStorage.loadAll(path, null, 0, 0, true, pixelScale, true);
+
+            assertNotNull(imageFrames);
+            assertEquals(1, imageFrames.length);
+            ImageFrame imageFrame = imageFrames[0];
+            assertNotNull(imageFrame);
+
+            assertEquals("Unexpected pixel scale",
+                    pixelScale, imageFrame.getPixelScale(), 0.0001f);
+
+            int width = imageFrame.getWidth();
+            int height = imageFrame.getHeight();
+            assertTrue("Image size must be at least 8x8", width >= 8 && height >= 8);
+
+            return imageFrame;
+        } catch (ImageStorageException ex) {
+            throw new RuntimeException(ex);
+        }
+    }
+
+    private void testPixelGet(float pixelScale) {
+        ImageFrame imageFrame = loadImage(imagePath, pixelScale);
+        int width = imageFrame.getWidth();
+        int height = imageFrame.getHeight();
+
+        // Convert to a Prism Image
+        Image image = Image.convertImageFrame(imageFrame);
+        assertNotNull(image);
+        assertEquals(width, image.getWidth());
+        assertEquals(height, image.getHeight());
+
+        // Test pixel read operations.
+        // NOTE: the x, y position passed into getArgb are unscaled,
+        // user-space coords in the range [0, (sz/pixelScale)-1]
+        int w = (int) (width / pixelScale);
+        int h = (int) (height / pixelScale);
+
+        // Test pixel read at the center and all 4 corners.
+        // In each of these cases we will read the pixel twice to
+        // ensure that the value remains stable, and that we don't
+        // get an IOOBE.
+
+        final int[] xvals = {
+            w / 2,
+            2,
+            w - 2,
+            2,
+            w - 2
+        };
+
+        final int[] yvals = {
+            h / 2,
+            2,
+            2,
+            h - 2,
+            h - 2
+        };
+
+        final int[] exColors = {
+            0xffff00ff, // CENTER
+            0xffff0000, // TOP LEFT
+            0xff0000ff, // TOP RIGHT
+            0xffff8080, // BOTTOM LEFT
+            0xff8ff080  // BOTTOM RIGHT
+        };
+
+        for (int i = 0; i < xvals.length; i++) {
+            int pix1 = image.getArgb(xvals[i], yvals[i]);
+            assertEquals("getArgb returns incorrect color", exColors[i], pix1);
+            int pix2 = image.getArgb(xvals[i], yvals[i]);
+            assertEquals("second call to getArgb returns different result", pix1, pix2);
+        }
+    }
+
+    @Test
+    public void testNormalPixelGet() {
+        // Test image with pixel scale of 1, which will load the unscaled image
+        testPixelGet(1.0f);
+    }
+
+    @Test
+    public void testScaledPixelGet() {
+        // Test image with pixel scale of 2, which will load the @2x image file
+        testPixelGet(2.0f);
+    }
+
+    @Test
+    public void testScaledImageSize() {
+        // Load both the normal and the @2x images
+        ImageFrame imageFrame1 = loadImage(imagePath, 1.0f);
+        ImageFrame imageFrame2 = loadImage(imagePath, 2.0f);
+
+        // Check that the size of the @2x image is twice that of the normal image
+        int exWidth2 = imageFrame1.getWidth() * 2;
+        int exHeight2 = imageFrame1.getHeight()* 2;
+        assertEquals("width of @2x image is wrong", exWidth2, imageFrame2.getWidth());
+        assertEquals("height of @2x image is wrong", exHeight2, imageFrame2.getHeight());
+    }
+
+}