BoofCV on Android - threshold() returns black image

Question

 Bitmap blurredBitmap = GaussianBlur.with(sApp.getApplicationContext()).radius(5).render(R.drawable.test_img_divider);
        GrayU8 imageGray = ConvertBitmap.bitmapToGray(blurredBitmap,(GrayU8) null, null);
        GrayU8 imageThreshold = GThresholdImageOps.threshold(imageGray, null, GThresholdImageOps.computeEntropy(imageGray, 0, 255), true);

        Bitmap output = Bitmap.createBitmap(imageThreshold.width, imageThreshold.height, Bitmap.Config.ARGB_8888);
        ConvertBitmap.grayToBitmap(imageThreshold, output, null); // output is totally black.

R.drawable.test_img_divider:

blurredBitmap:

imageGray(after it was converted to bitmap):

output:

Answer 1

I ran into this too. The image is actually not black. The pixels all have a value of either 0 or 1. But 1 looks pretty much the same as 0 if you treat the image as something that could have pixel values anywhere up to 255.

One way to deal with this is to use forEachPixel() to multiply each pixel value by 255.