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How to add Gaussian noise using JAVA

asked 2019-01-08 17:28:17 -0500

cz11@hw.ac.uk gravatar image

updated 2019-01-08 22:42:36 -0500

berak gravatar image
    Mat grayMat = new Mat();
    Mat noiseMat = new Mat();
    BitmapFactory.Options o = new BitmapFactory.Options();
    o.inDither=false;
    o.inSampleSize=1;
    int width = grayBitmap.getWidth();
    int height= grayBitmap.getHeight();
    noiseBitmap=Bitmap.createBitmap(width,height,Bitmap.Config.ALPHA_8);
    //bitmap to MAT
    Utils.bitmapToMat(grayBitmap,grayMat);
    GaussianNoise = grayMat.clone();

I don't know how to do next, to generate a Mat which is the same size as grayMat and then add them together.

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answered 2019-01-08 22:21:55 -0500

berak gravatar image

updated 2019-01-08 22:38:14 -0500

first, forget about the silly Bitmaps, you'll never need any here.

Mat noise = new Mat(img.size(), img.type());

then, for gaussian noise, you'll need the mean and stdev of your image:

MatOfDouble mean = new MatOfDouble ();
MatOfDouble dev = new MatOfDouble ();

Core.meanStdDev(img,mean,dev);

// the java wrappers allow only to apply single numbers here, imho, that's a bug !
//  if your img has more than 1 channel, you might need to split() it into seperate 
//  channels, apply noise on each seperately, and merge() the results
Core.randn(noise,mean.get(0,0)[0], dev.get(0,0)[0]);

Core.add(img, noise, img);

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Thank you for your reply, but I think this noise is too big, I just want a noise which mean is 0 and dev is 0.1, so I use Core.randn (noise,0,1), but after I add it with gray mat, it will not work and Error shows that:Error: Sizes of input arguments do not match (The operation is neither 'array op array' (where arrays have the same size and the same number of channels), nor 'array op scalar', nor 'scalar op array') in void cv::arithm_op(cv::InputArray, cv::InputArray, cv::OutputArray, cv::InputArray, int, void (*)(const uchar, size_t, const uchar, size_t, uchar, size_t, int, int, void), bool, void, int), file /build/master_pack-android/opencv/modules/core/src/arithm.cpp, line 659.Could you help me to solve this problem? thank you in advance.

cz11@hw.ac.uk gravatar imagecz11@hw.ac.uk ( 2019-01-21 20:55:22 -0500 )edit
  • you can apply noise on the desired image itself, you don't need a 2nd one
  • if you try to add 2 images they need to have the same size, type and number of channels (not hard to understand, right ?)
berak gravatar imageberak ( 2019-01-22 01:04:57 -0500 )edit
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Asked: 2019-01-08 17:28:17 -0500

Seen: 170 times

Last updated: Jan 08