CODEWITHSUNDEEP
javaandroidopencvbitmapmat
Andreas Dimas
Andreas Dimas

Reputation: 51

Converting bitmap to mat in Java for image processing

Hi i want to do image processing by using openCV in my Java Android project. So now i'm having issue when reading the image file and convert it into mat. I've tried by reading the image directly and read it as Mat but still doesn't work:

//get image source from folder
    String imgPath =  Environment.getExternalStorageDirectory().toString() + "/SimpleAndroidOCR/ocr.jpg";
    Mat sourceImage = Imgcodecs.imread(imgPath);

Then I tried to get the bitmap and convert it to Mat but still doesn't work:

Bitmap bitmap1 = BitmapFactory.decodeFile(_path, options);
Mat sourceImage = new Mat();
Utils.bitmapToMat(bitmap1 , sourceImage);

Could anyone tell me what did I do wrong? Thanks in advance

Upvotes: 3

Views: 5888

Answers (2)

Andreas Dimas
Andreas Dimas

Reputation: 51

I found solution for my own issue. I'm referring to this Android & OpenCV : Utils.bitmapToMat crashes whereby it mentions that we need to load the library in order to use openCV related code Here is my code to load the library:

 private BaseLoaderCallback mLoaderCallBack = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        if(status == LoaderCallbackInterface.SUCCESS){

        }else{
            super.onManagerConnected(status);
        }

    }
};

public void onResume(){
    super.onResume();
    OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_1_0, this, mLoaderCallBack);
}

Please take note that you should change the opencv version to match with version that you use.

In order to convert bitmap to mat i'm referring to this https://groups.google.com/forum/#!topic/android-opencv/8EoxpTb4W3E bitmaptomat only works when we have proper bitmap format which is ARGB_8888 Here is my code:

    private Bitmap JPGtoRGB888(Bitmap img){
        Bitmap result = null;

        int numPixels = img.getWidth() * img.getHeight();
        int[] pixels = new int[numPixels];

//        get jpeg pixels, each int is the color value of one pixel
        img.getPixels(pixels,0,img.getWidth(),0,0,img.getWidth(),img.getHeight());

//        create bitmap in appropriate format
        result = Bitmap.createBitmap(img.getWidth(),img.getHeight(), Bitmap.Config.ARGB_8888);

//        Set RGB pixels
        result.setPixels(pixels, 0, result.getWidth(), 0, 0, result.getWidth(), result.getHeight());

        return result;
    }

This function will be called here

Bitmap bmp32 = JPGtoRGB888(bitmap);
Mat sourceImage = new Mat();
Utils.bitmapToMat(bmp32, sourceImage);

Then you can process the sourceImage Hope this is helpful Cheers!

Upvotes: 2

ZdaR
ZdaR

Reputation: 22954

As you are using OpenCV with android, So there are two possibilities:

  • The path of the image that you are giving may not be there, try logging your image path, and check if that really exists.

  • If you are completely sure that the path is valid, then check if you have defined the permission of External Storage read/write in the Manifest file of your android project.

Upvotes: 0

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