Это можно сделать с помощью класса действий
Actions crop = new Actions(driver);
private By elementBy = By.cssSelector("<css selector for the element>");
//Move to the desired co-ordinates of the image element, In the code below I am staring from bottom left corner of the image
crop.moveToElement(driver.findElement(elementBy),0,0);
//locate the co-ordinates of image you want to move by and perform the click and hold which mimics the crop action
crop.clickAndHold().moveByOffset(196,238).release().build().perform();