在使用 Appium 和 opencv 进行图像比较时，可能会遇到 org.openqa.selenium.UnsupportedCommandException 异常，原因是 Appium 驱动不支持 opencv 提供的相关操作。因此，需要使用 WebDriverWaits 和 MobileCommands 接口来实现图像比较功能。

以下是示例代码：

public class ImageComparison {
    private AppiumDriver driver;
    private OpenCV opencv;
    
    public ImageComparison(AppiumDriver driver) {
        this.driver = driver;
        this.opencv = new OpenCV();
    }
    
    public boolean compareImages(String path1, String path2) {
        Mat img1 = opencv.imread(path1);
        Mat img2 = opencv.imread(path2);
        Mat diff = new Mat();
        opencv.absdiff(img1, img2, diff);
        double diffPercent = (opencv.countNonZero(diff) * 100) / (img1.width() * img1.height());
        if (diffPercent == 0) {
            return true;
        }
        return false;
    }
    
    // 使用WebDriverWaits和MobileCommands接口
    public boolean waitForImage(String path) {
        WebDriverWait wait = new WebDriverWait(driver, 10);
        driver.executeScript("mobile: animation", ImmutableMap.of("action", "none"));
        ExpectedCondition imageLoaded = new ExpectedCondition() {
            public Boolean apply(WebDriver driver) {
                return compareImages(path, "/sdcard/screenshot.png");
            }
        }
        return wait.until(imageLoaded);
    }
}

上述代码中，compareImages() 方法使用 opencv 库来比较两张图片，并返回比较结果。waitForImage() 方法通过 WebDriverWaits 和 MobileCommands 接口等待加载指定的图像，并返回比较结果。可以根据具体需要进行调整。