Add ScreenshotState class for screenshots comparison purposes

Author: Mykola Mokhnach

build.gradle

@@ -66,6 +66,7 @@ dependencies {
     compile 'commons-io:commons-io:2.5'
     compile 'org.springframework:spring-context:4.3.5.RELEASE'
     compile 'org.aspectj:aspectjweaver:1.8.10'
+    compile 'nu.pattern:opencv:2.4.9-7'
 
     testCompile 'junit:junit:4.12'
 }

src/main/java/io/appium/java_client/ScreenshotState.java

@@ -0,0 +1,326 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.appium.java_client;
+
+import org.opencv.core.Core;
+import org.opencv.core.CvType;
+import org.opencv.core.Mat;
+import org.opencv.core.Size;
+import org.opencv.imgproc.Imgproc;
+
+import java.awt.AlphaComposite;
+import java.awt.Graphics2D;
+import java.awt.image.BufferedImage;
+import java.awt.image.DataBufferByte;
+import java.util.Optional;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public class ScreenshotState {
+    private static final long DEFAULT_INTERVAL_MS = 500;
+
+    private Optional<BufferedImage> previousScreenshot = Optional.empty();
+    private Supplier<BufferedImage> stateProvider;
+
+    private long comparisonIntervalMs = DEFAULT_INTERVAL_MS;
+
+    /**
+     * The class constructor accepts single argument, which is
+     * lambda function, that provides the screenshot of the necessary
+     * screen area to be verified for similarity.
+     * This lambda method is NOT called upon class creation.
+     * One has to invoke {@link #remember()} method in order to call it.
+     *
+     * <p>Examples of provider function with Appium driver:
+     * <code>
+     * () -&gt; {
+     * final byte[] srcImage = ((TakesScreenshot) driver).getScreenshotAs(OutputType.BYTES);
+     * return ImageIO.read(new ByteArrayInputStream(srcImage));
+     * }
+     * </code>
+     * or
+     * <code>
+     * () -&gt; {
+     * final byte[] srcImage = ((TakesScreenshot) driver).getScreenshotAs(OutputType.BYTES);
+     * final BufferedImage screenshot = ImageIO.read(new ByteArrayInputStream(srcImage));
+     * final WebElement element = driver.findElement(locator);
+     * // Can be simplified in Selenium 3.0+ by using getRect method of WebElement interface
+     * final Point elementLocation = element.getLocation();
+     * final Dimension elementSize = element.getSize();
+     * return screenshot.getSubimage(
+     * new Rectangle(elementLocation.x, elementLocation.y, elementSize.width, elementSize.height);
+     * }
+     * </code>
+     *
+     * @param stateProvider lambda function, which returns a screenshot for further comparison
+     */
+    public ScreenshotState(Supplier<BufferedImage> stateProvider) {
+        this.stateProvider = stateProvider;
+    }
+
+    /**
+     * Gets the interval value in ms between similarity verification rounds in <em>verify*</em> methods.
+     *
+     * @return current interval value in ms
+     */
+    public long getComparisonInterval() {
+        return comparisonIntervalMs;
+    }
+
+    /**
+     * Sets the interval between similarity verification rounds in <em>verify*</em> methods.
+     *
+     * @param ms interval value in ms. 500 by default
+     * @return self instance for chaining
+     */
+    public ScreenshotState setComparisonInterval(long ms) {
+        this.comparisonIntervalMs = ms;
+        return this;
+    }
+
+    /**
+     * Call this method to save the initial screenshot state.
+     * It is mandatory to call before any <em>verify*</em> method is invoked.
+     *
+     * @return self instance for chaining
+     */
+    public ScreenshotState remember() {
+        this.previousScreenshot = Optional.of(stateProvider.get());
+        return this;
+    }
+
+    /**
+     * This method allows to pass a custom bitmap for further comparison
+     * instead of taking one using screenshot provider function. This might
+     * be useful in some advanced cases.
+     *
+     * @param customInitialState valid bitmap
+     * @return self instance for chaining
+     */
+    public ScreenshotState remember(BufferedImage customInitialState) {
+        this.previousScreenshot = Optional.of(customInitialState);
+        return this;
+    }
+
+    public static class ScreenshotComparisonError extends RuntimeException {
+        private static final long serialVersionUID = -7011854909939194466L;
+
+        ScreenshotComparisonError(Throwable reason) {
+            super(reason);
+        }
+
+        ScreenshotComparisonError(String message) {
+            super(message);
+        }
+    }
+
+    public static class ScreenshotComparisonTimeout extends RuntimeException {
+        private static final long serialVersionUID = 6336247721154252476L;
+        private double currentScore = Double.NaN;
+
+        ScreenshotComparisonTimeout(String message, double currentScore) {
+            super(message);
+            this.currentScore = currentScore;
+        }
+
+        public double getCurrentScore() {
+            return currentScore;
+        }
+    }
+
+    private ScreenshotState checkState(Function<Double, Boolean> checkerFunc, long timeoutMs) {
+        return checkState(checkerFunc, timeoutMs, ResizeMode.NO_RESIZE);
+    }
+
+    private ScreenshotState checkState(Function<Double, Boolean> checkerFunc, long timeoutMs, ResizeMode resizeMode) {
+        final long started = System.currentTimeMillis();
+        double score;
+        do {
+            final BufferedImage currentState = stateProvider.get();
+            score = getOverlapScore(this.previousScreenshot
+                    .orElseThrow(() -> new ScreenshotComparisonError("Initial screenshot state is not set. "
+                            + "Nothing to compare")), currentState, resizeMode);
+            if (checkerFunc.apply(score)) {
+                return this;
+            }
+            try {
+                Thread.sleep(comparisonIntervalMs);
+            } catch (InterruptedException e) {
+                throw new ScreenshotComparisonError(e);
+            }
+        }
+        while (System.currentTimeMillis() - started <= timeoutMs);
+        throw new ScreenshotComparisonTimeout(
+                String.format("SScreenshot comparison timed out after %s ms. Actual similarity score: %.5f",
+                        timeoutMs, score), score);
+    }
+
+    /**
+     * Verifies whether the state of the screenshot provided by stateProvider lambda function
+     * is changed within the given timeout.
+     *
+     * @param timeoutMs timeout value in milliseconds
+     * @param minScore  the value in range (0.0, 1.0)
+     * @return self instance for chaining
+     * @throws ScreenshotComparisonTimeout if the calculated score is still
+     *                                     greater or equal to the given score after timeout happens
+     * @throws ScreenshotComparisonError   if {@link #remember()} method has not been invoked yet
+     */
+    public ScreenshotState verifyChanged(long timeoutMs, double minScore) {
+        return checkState((x) -> x < minScore, timeoutMs);
+    }
+
+    /**
+     * Verifies whether the state of the screenshot provided by stateProvider lambda function
+     * is changed within the given timeout.
+     *
+     * @param timeoutMs  timeout value in milliseconds
+     * @param minScore   the value in range (0.0, 1.0)
+     * @param resizeMode one of <em>ResizeMode</em> enum values.
+     *                   Set it to a value different from <em>NO_RESIZE</em>
+     *                   if the actual screenshot is expected to have different
+     *                   dimensions in comparison to the previously remembered one
+     * @return self instance for chaining
+     * @throws ScreenshotComparisonTimeout if the calculated score is still
+     *                                     greater or equal to the given score after timeout happens
+     * @throws ScreenshotComparisonError   if {@link #remember()} method has not been invoked yet
+     */
+    public ScreenshotState verifyChanged(long timeoutMs, double minScore, ResizeMode resizeMode) {
+        return checkState((x) -> x < minScore, timeoutMs, resizeMode);
+    }
+
+    /**
+     * Verifies whether the state of the screenshot provided by stateProvider lambda function
+     * is not changed within the given timeout.
+     *
+     * @param timeoutMs timeout value in milliseconds
+     * @param minScore  the value in range (0.0, 1.0)
+     * @return self instance for chaining
+     * @throws ScreenshotComparisonTimeout if the calculated score is still
+     *                                     less than the given score after timeout happens
+     * @throws ScreenshotComparisonError   if {@link #remember()} method has not been invoked yet
+     */
+    public ScreenshotState verifyNotChanged(long timeoutMs, double minScore) {
+        return checkState((x) -> x >= minScore, timeoutMs);
+    }
+
+    /**
+     * Verifies whether the state of the screenshot provided by stateProvider lambda function
+     * is changed within the given timeout.
+     *
+     * @param timeoutMs  timeout value in milliseconds
+     * @param minScore   the value in range (0.0, 1.0)
+     * @param resizeMode one of <em>ResizeMode</em> enum values.
+     *                   Set it to a value different from <em>NO_RESIZE</em>
+     *                   if the actual screenshot is expected to have different
+     *                   dimensions in comparison to the previously remembered one
+     * @return self instance for chaining
+     * @throws ScreenshotComparisonTimeout if the calculated score is still
+     *                                     less than the given score after timeout happens
+     * @throws ScreenshotComparisonError   if {@link #remember()} method has not been invoked yet
+     */
+    public ScreenshotState verifyNotChanged(long timeoutMs, double minScore, ResizeMode resizeMode) {
+        return checkState((x) -> x >= minScore, timeoutMs, resizeMode);
+    }
+
+    private static Mat prepareImageForComparison(BufferedImage srcImage) {
+        final BufferedImage result = new BufferedImage(srcImage.getWidth(), srcImage.getHeight(),
+                BufferedImage.TYPE_3BYTE_BGR);
+        final Graphics2D g = srcImage.createGraphics();
+        try {
+            g.setComposite(AlphaComposite.Src);
+            g.drawImage(srcImage, 0, 0, null);
+        } finally {
+            g.dispose();
+        }
+        final byte[] pixels = ((DataBufferByte) result.getRaster().getDataBuffer()).getData();
+        final Mat imageMat = new Mat(result.getHeight(), result.getWidth(), CvType.CV_8UC3);
+        imageMat.put(0, 0, pixels);
+        return imageMat;
+    }
+
+    private static Mat resizeFirstMatrixToSecondMatrixResolution(Mat first, Mat second) {
+        if (first.width() != second.width() || first.height() != second.height()) {
+            final Mat result = new Mat();
+            final Size sz = new Size(second.width(), second.height());
+            Imgproc.resize(first, result, sz);
+            return result;
+        }
+        return first;
+    }
+
+    /**
+     * A shortcut to {@link #getOverlapScore(BufferedImage, BufferedImage, ResizeMode)} method
+     * for the case if both reference and template images are expected to have the same dimensions.
+     *
+     * @param refImage reference image
+     * @param tplImage template
+     * @return similarity score value in range (-1.0, 1.0). 1.0 is returned if the images are equal
+     * @throws ScreenshotComparisonError if provided images are not valid or have different resolution
+     */
+    public static double getOverlapScore(BufferedImage refImage, BufferedImage tplImage) {
+        return getOverlapScore(refImage, tplImage, ResizeMode.NO_RESIZE);
+    }
+
+    /**
+     * Compares two valid java bitmaps and calculates similarity score between them.
+     *
+     * @param refImage   reference image
+     * @param tplImage   template
+     * @param resizeMode one of possible enum values. Set it either to <em>TEMPLATE_TO_REFERENCE_RESOLUTION</em> or
+     *                   <em>REFERENCE_TO_TEMPLATE_RESOLUTION</em> if given bitmaps have different dimensions
+     * @return similarity score value in range (-1.0, 1.0). 1.0 is returned if the images are equal
+     * @throws ScreenshotComparisonError if provided images are not valid or have
+     *                                   different resolution, but resizeMode has been set to <em>NO_RESIZE</em>
+     */
+    public static double getOverlapScore(BufferedImage refImage, BufferedImage tplImage, ResizeMode resizeMode) {
+        Mat ref = prepareImageForComparison(refImage);
+        if (ref.empty()) {
+            throw new ScreenshotComparisonError("Reference image cannot be converted for further comparison");
+        }
+        Mat tpl = prepareImageForComparison(tplImage);
+        if (tpl.empty()) {
+            throw new ScreenshotComparisonError("Template image cannot be converted for further comparison");
+        }
+        switch (resizeMode) {
+            case TEMPLATE_TO_REFERENCE_RESOLUTION:
+                tpl = resizeFirstMatrixToSecondMatrixResolution(tpl, ref);
+                break;
+            case REFERENCE_TO_TEMPLATE_RESOLUTION:
+                ref = resizeFirstMatrixToSecondMatrixResolution(ref, tpl);
+                break;
+            default:
+                // do nothing
+        }
+
+        if (ref.width() != tpl.width() || ref.height() != tpl.height()) {
+            throw new ScreenshotComparisonError(
+                    "Resolutions of template and reference images are expected to be equal. "
+                            + "Try different resizeMode value."
+            );
+        }
+
+        final Mat res = new Mat(ref.rows() - tpl.rows() + 1, ref.cols() - tpl.cols() + 1, CvType.CV_32FC1);
+        Imgproc.matchTemplate(ref, tpl, res, Imgproc.TM_CCOEFF_NORMED);
+        Core.MinMaxLocResult minMaxLocResult = Core.minMaxLoc(res);
+        return minMaxLocResult.maxVal;
+    }
+
+    public enum ResizeMode {
+        NO_RESIZE, TEMPLATE_TO_REFERENCE_RESOLUTION, REFERENCE_TO_TEMPLATE_RESOLUTION
+    }
+}