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### how to detect if image is grayscale java

i like to know how to detect grayscale image, i tried using

Mat matImages = new Mat();

and then i take bitmap and convert it on that's mat when check the channel i got number 4

public String getChannel(Bitmap bitmap){
Mat matImages = new Mat();
Utils.bitmapToMat(bitmap, matImages);
String value = String.valueOf(matImages.channels());
return value;
}


the value i got is 4 when i try to check the channel of images, i like to detect channel with something like if channel = 1 i got grayscale image and when i got channel =3 i got rgb images. But, the only output i got is 4 channel. Can anyone explain it to me how that's can be happening