参考这篇文章和这篇问答,我编写了以下两个函数来尝试检测图像是否模糊:
public static boolean checkIfImageIsBlurred(BitmapRegionDecoder bitmapRegionDecoder) {
if (bitmapRegionDecoder == null) {
Timber.e("Expected bitmapRegionDecoder was null");
return true;
}
int loadImageHeight = bitmapRegionDecoder.getHeight();
int loadImageWidth = bitmapRegionDecoder.getWidth();
int checkImageTopPosition = 0;
int checkImageBottomPosition = loadImageHeight / 10;
int checkImageLeftPosition = 0;
int checkImageRightPosition = loadImageWidth / 10;
int totalDividedRectangles = 0;
int numberOfBlurredRectangles = 0;
while ((checkImageRightPosition <= loadImageWidth) && (checkImageLeftPosition < checkImageRightPosition)) {
while ((checkImageBottomPosition <= loadImageHeight) && (checkImageTopPosition < checkImageBottomPosition)) {
Timber.d("left: " + checkImageLeftPosition + " right: " + checkImageRightPosition + " top: " + checkImageTopPosition + " bottom: " + checkImageBottomPosition);
Rect rect = new Rect(checkImageLeftPosition,checkImageTopPosition,checkImageRightPosition,checkImageBottomPosition);
totalDividedRectangles++;
Bitmap processBitmap = bitmapRegionDecoder.decodeRegion(rect,null);
if (checkIfImageIsBlurred(processBitmap)) {
numberOfBlurredRectangles++;
}
checkImageTopPosition = checkImageBottomPosition;
checkImageBottomPosition += (checkImageBottomPosition < (loadImageHeight - checkImageBottomPosition)) ? checkImageBottomPosition: (loadImageHeight - checkImageBottomPosition);
}
checkImageTopPosition = 0; //reset to start
checkImageBottomPosition = loadImageHeight / 10; //reset to start
checkImageLeftPosition = checkImageRightPosition;
checkImageRightPosition += (checkImageRightPosition < (loadImageWidth - checkImageRightPosition)) ? checkImageRightPosition : (loadImageWidth - checkImageRightPosition);
}
Timber.d("blurred rectangles count = " + numberOfBlurredRectangles + ", total rectangles count = " + totalDividedRectangles);
return numberOfBlurredRectangles > totalDividedRectangles * 0.50;
}
public static boolean checkIfImageIsBlurred(Bitmap bitmap) {
if(bitmap == null) {
Timber.e("Expected bitmap was null");
return false;
}
Mat imageBitmapMat = new Mat(bitmap.getWidth(),bitmap.getHeight(),CvType.CV_8UC1);
Utils.bitmapToMat(bitmap,imageBitmapMat);
Mat grayscaleBitmapMat = new Mat();
Imgproc.cvtColor(imageBitmapMat,grayscaleBitmapMat,Imgproc.COLOR_RGB2GRAY);
Mat postLaplacianMat = new Mat();
Imgproc.Laplacian(grayscaleBitmapMat,postLaplacianMat,3);
MatOfDouble mean = new MatOfDouble();
MatOfDouble standardDeviation = new MatOfDouble();
Core.meanStdDev(postLaplacianMat,mean,standardDeviation);
double result = Math.pow(standardDeviation.get(0,0)[0],2);
Timber.d("blurry result = " + result);
return result < 100;
}
由于从相机拍摄的图像太大,我使用BitmapRegionDecoder获取它们的部分,然后检查该部分整个图像是否模糊。如果拉普拉斯变换的变化小于所定义的阈值,则将该图像声明为模糊,而在这种情况下,该阈值为100(此值从第一个附加文章中选择)。如果发现50%以上的图像“部分”模糊,则认为整个图像模糊。
经过测试,我发现结果不确定。几乎我测试的所有图像都被声明为模糊。我甚至尝试修改使用的拉普拉斯变换的变化阈值,但没有找到一个提供一致正确结果的值,这让我想我做错了什么。