我试图比较位于我的操作系统机器下的两个图像。我在我的os机器上运行ImageMagick。我正在使用这种方法：
public boolean compareImages (String expectedScreenShot, String capturedScreenShot, String pdiffCompare) {
// This instance wraps the compare command
ProcessStarter.setGlobalSearchPath("/usr/local/bin/");
//ImageCommand compare = new ImageCommand();
CompareCmd compare = new CompareCmd();
// For metric-output
compare.setErrorConsumer(StandardStream.STDERR);
IMOperation cmpOp = new IMOperation();
// Set the compare metric
cmpOp.metric("AE");
// Add the expected image
cmpOp.addImage(expectedScreenShot);
// Add the current image
cmpOp.addImage(capturedScreenShot);
// This stores the difference
cmpOp.addImage(pdiffCompare);
try {
// Do the compare
compare.run(cmpOp);
return true;
}
catch (Exception ex) {
return false;
}
}
我使用im4java：1.4.0但是当我运行compare.run（cmpOp）时;我收到这个例外：
org.im4java.core.CommandException：java.lang.NullPointerException
org.im4java.core.CommandException: java.lang.NullPointerException
at org.im4java.core.ImageCommand.run(ImageCommand.java:219)
at com.Pdiff.WebDriverExtensions.compareImages(WebDriverExtensions.java:118)
at com.Pdiff.WebDriverExtensions.screenShotMatches(WebDriverExtensions.java:67)
at com.stepdefs.identity.websites.SB3SubmitContactFormStepDefs.accessToSiteBuilder(SB3SubmitContactFormStepDefs.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at cucumber.runtime.Utils$1.call(Utils.java:40)
at cucumber.runtime.Timeout.timeout(Timeout.java:16)
at cucumber.runtime.Utils.invoke(Utils.java:34)
at cucumber.runtime.java.JavaStepDefinition.execute(JavaStepDefinition.java:37)
at cucumber.runtime.StepDefinitionMatch.runStep(StepDefinitionMatch.java:37)
at cucumber.runtime.Runtime.runStep(Runtime.java:300)
at cucumber.runtime.model.StepContainer.runStep(StepContainer.java:44)
at cucumber.runtime.model.StepContainer.runSteps(StepContainer.java:39)
at cucumber.runtime.model.CucumberScenario.run(CucumberScenario.java:44)
at cucumber.runtime.junit.ExecutionUnitRunner.run(ExecutionUnitRunner.java:91)
at cucumber.runtime.junit.FeatureRunner.runChild(FeatureRunner.java:63)
at cucumber.runtime.junit.FeatureRunner.runChild(FeatureRunner.java:18)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at cucumber.runtime.junit.FeatureRunner.run(FeatureRunner.java:70)
at cucumber.api.junit.Cucumber.runChild(Cucumber.java:93)
at cucumber.api.junit.Cucumber.runChild(Cucumber.java:37)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at cucumber.api.junit.Cucumber.run(Cucumber.java:98)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:105)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:56)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:64)
at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:50)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
at org.gradle.messaging.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:106)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.messaging.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:360)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
任何帮助将不胜感激。