I am developing an app for clicked an image and convert the bitmap to binary. Here is some of my code of converting the image to binary:
File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/Watershed/WatershedImages", "Image_"+Save.MyDate+".jpg");
Mat origianlImage = Imgcodecs.imread(file.getAbsolutePath());
Mat image1Mat = new Mat();
Imgproc.cvtColor(origianlImage,image1Mat, Imgproc.COLOR_BGR2HSV);
Mat mat3 = new Mat();
Core.inRange(image1Mat, new Scalar(0, 0, 0), new Scalar(50, 255, 255), mat3);
Mat mat4 = new Mat();
Imgproc.threshold(mat3, mat4, 0, 255, Imgproc.THRESH_BINARY);
Bitmap threshBitmap = Bitmap.createBitmap(mat4.cols(), mat4.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(mat4, threshBitmap);
The image is converted to bitmap. I have checked the color of pixels and found out that black pixel value is -16777216 and white is -1. For further processing, I need to change these values to original java type (0 for black and 255 for white).
How to manipulate the pixel values from -16777216 to 0 and -1 to 255 WITHOUT changing the colors? Is there any way? Please help.
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I am using OpenCV android library thresholding method for image segmentation, but the problem is that the output bitmap contains black background which I do not want please note that original image does not have any black background it is actually white. I am attaching the code for your reference, I am new to opencv and don't have much understanding about it also so kindly help me out.
private void Segmentation() {
Mat srcMat = new Mat();
gray = new Mat();
Utils.bitmapToMat(imageBmp, srcMat);
Imgproc.cvtColor(srcMat, gray, Imgproc.COLOR_RGBA2GRAY);
grayBmp = Bitmap.createBitmap(imageBmp.getWidth(), imageBmp.getHeight(), Bitmap.Config.RGB_565);
Utils.matToBitmap(gray, grayBmp);
grayscaleHistogram();
Mat threshold = new Mat();
Imgproc.threshold(gray, threshold, 0, 255, Imgproc.THRESH_BINARY_INV + Imgproc.THRESH_OTSU);
thresBmp = Bitmap.createBitmap(imageBmp.getWidth(), imageBmp.getHeight(), Bitmap.Config.RGB_565);
Utils.matToBitmap(threshold, thresBmp);
Mat closing = new Mat();
Mat kernel = Mat.ones(5, 5, CvType.CV_8U);
Imgproc.morphologyEx(threshold, closing, Imgproc.MORPH_CLOSE, kernel, new Point(-1, -1), 3);
closingBmp = Bitmap.createBitmap(imageBmp.getWidth(), imageBmp.getHeight(), Bitmap.Config.RGB_565);
Utils.matToBitmap(closing, closingBmp);
result = new Mat();
Core.subtract(closing, gray, result);
Core.subtract(closing, result, result);
resultBmp = Bitmap.createBitmap(imageBmp.getWidth(), imageBmp.getHeight(), Bitmap.Config.RGB_565);
Utils.matToBitmap(result, resultBmp);
Glide.with(ResultActivity.this).asBitmap().load(resultBmp).into(ivAfter);
}
enter image description here
What exactly do you want it to be then? Binary thresholding works like this:
if value < threshold:
value = 0
else:
value = 1
Of course you can convert it to a grayscale / RGB image and adjust the background to your liking. You can also invert your image (white background, black segmentation) by using the ~ operator.
segmented_image = ~ segmented_image
Edit: OpenCV has a dedicated flag to invert the results: CV_THRESH_BINARY_INV You are already using it, maybe try changing it to CV_THRESH_BINARY
I m working on optical mark recognition. My purpose is extracting the red circles from the image and evaluating black shapes after. There is no problem on detecting red circles and extracting them (picture 2), i successfully obtain the image where red pixels are transparent. The problem is that, when i convert this image to grey, transparent pixels becomes black, so nothing changes after all this effort(picture3). How can i convert transparent pixels to white or am I making somethings very wrong?
Mat masked = new Mat(src.size(), CvType.CV_8UC3, new Scalar(255, 255, 255));
Mat hsv_image = new Mat();
Imgproc.cvtColor(src, hsv_image, Imgproc.COLOR_RGB2HSV);
// create mask starts
Mat lower_red_hue_range = new Mat();
Mat upper_red_hue_range = new Mat();
Core.inRange(hsv_image, new Scalar(0, 70, 70), new Scalar(10, 255, 255), lower_red_hue_range);
Core.inRange(hsv_image, new Scalar(160, 70, 70), new Scalar(179, 255, 255), upper_red_hue_range);
Mat red_hue_mask = new Mat();
Core.addWeighted(lower_red_hue_range, 1.0, upper_red_hue_range, 1.0, 0.0, red_hue_mask);
Core.bitwise_not(red_hue_mask, red_hue_mask);
Utils.saveAsBitmap(red_hue_mask); // picture1
// create mask ends
// apply mask to src
src.copyTo(masked, red_hue_mask);
Utils.saveAsBitmap(masked); // picture2 -> now it has transparent pixels
// convert to greyscale (transparent pixels become black :( )
Imgproc.cvtColor(masked, mBlacked, Imgproc.COLOR_RGB2GRAY);
Utils.saveAsBitmap(mBlacked); // picture3
picture src
picture 1-2-3
> Hi, I am using OpenCV android library grabcut() method to extract an image from background, but the problem is that the output bitmap contains background Same as original image and object become white .I need Object as its same as original image and background transparent
I am using this code
private static Bitmap makeBlackTransparent(Bitmap image) {
// convert image to matrix
Mat src = new Mat(image.getWidth(), image.getHeight(), CvType.CV_8UC4);
Utils.bitmapToMat(image, src);
// init new matrices
Mat dst = new Mat(image.getWidth(), image.getHeight(), CvType.CV_8UC4);
Mat tmp = new Mat(image.getWidth(), image.getHeight(), CvType.CV_8UC4);
Mat alpha = new Mat(image.getWidth(), image.getHeight(), CvType.CV_8UC4);
// convert image to grayscale
Imgproc.cvtColor(src, tmp, Imgproc.COLOR_BGR2GRAY);
// threshold the image to create alpha channel with complete transparency in black background region and zero transparency in foreground object region.
Imgproc.threshold(tmp, alpha, 100, 255, Imgproc.THRESH_BINARY);
// split the original image into three single channel.
List<Mat> rgb = new ArrayList<Mat>(3);
Core.split(src, rgb);
// Create the final result by merging three single channel and alpha(BGRA order)
List<Mat> rgba = new ArrayList<Mat>(4);
rgba.add(rgb.get(0));
rgba.add(rgb.get(1));
rgba.add(rgb.get(2));
rgba.add(alpha);
Core.merge(rgba, dst);
// convert matrix to output bitmap
Bitmap output = Bitmap.createBitmap(image.getWidth(), image.getHeight(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(dst, output);
return output;
}
There are 2 problems in your code:
Firstly you need to segment out the white background, so adjust your thresh to be near 220 - 240 and also use THRESH_BINARY_INV instead of THRESH_BINARY :
Imgproc.threshold(tmp, alpha, 230, 255, Imgproc.THRESH_BINARY_INV);
Secondly, you must pre-multiply the ARGB layers, as Android ImageView behaves weird without premultiplication, for that you need to use cvtColor with COLOR_RGBA2mRGBA flag:
// Create the final result by merging three single channel and alpha(BGRA order)
List<Mat> rgba = new ArrayList<Mat>(4);
rgba.add(rgb.get(0));
rgba.add(rgb.get(1));
rgba.add(rgb.get(2));
rgba.add(alpha);
Core.merge(rgba, dst);
Imgproc.cvtColor(dst, dst, Imgproc.COLOR_RGBA2mRGBA);
I started with the following image, named rgbaMat4Mask.bmp:
Then I converted it to HSV, and then did inRange() to find contours, and got the following Mat named maskedMat:
Then I went on to draw the first contour (the bigger one), on a newly created empty Mat named newMatWithMask, which has been given the same size as that of the first image I started with:
So far so good, but the problem starts now. I created a new Mat and gave it the same size as that of the first contour (the bigger one), and then set its background color to new Scalar(120, 255, 255). Then I copied the newMat4MaskFinished to it using copyTo function. But neither is the size of the resulting Mat same as that of the contour, nor is its background color set to new Scalar(120, 255, 255) which is blue.
It is rather an image with size same as that of the entire mask, and has a black background. why? What am I doing wrong?
public void doProcessing(View view) {
// READING THE RGBA MAT
Mat rgbaMat4Mask = Highgui.imread("/mnt/sdcard/DCIM/rgbaMat4Mask.bmp");
// CONVERTING TO HSV
Mat hsvMat4Mask = new Mat();
Imgproc.cvtColor(rgbaMat4Mask, hsvMat4Mask, Imgproc.COLOR_BGR2HSV);
Highgui.imwrite("/mnt/sdcard/DCIM/hsvMat4Mask.bmp", hsvMat4Mask);//check
// CREATING A FILTER/MASK FOR RED COLORED BLOB
Mat maskedMat = new Mat();
Core.inRange(hsvMat4Mask, new Scalar(0, 100, 100), new Scalar(10, 255, 255), maskedMat);
Highgui.imwrite("/mnt/sdcard/DCIM/maskedMat.bmp", maskedMat);// check
// COPYING THE MASK TO AN EMPTY MAT
// STEP 1:
List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
Imgproc.findContours(maskedMat, contours, new Mat(), Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_NONE);
//STEP 2:
Mat newMat4Mask = new Mat(rgbaMat4Mask.rows(), rgbaMat4Mask.cols(), CvType.CV_8UC1);
newMat4Mask.setTo(new Scalar(0));
Imgproc.drawContours(newMat4Mask, contours, 0, new Scalar(255), -1);//TODO Using -1 instead of CV_FILLED.
Highgui.imwrite("/mnt/sdcard/DCIM/newMatWithMask.bmp", newMat4Mask);// check
//STEP 3
Log.i(TAG, "HAPPY rows:"+contours.get(0).rows()+" columns:"+contours.get(0).cols());
Mat newMatwithMaskFinished = new Mat(contours.get(0).rows(), contours.get(0).cols(), CvType.CV_8UC3);
newMatwithMaskFinished.setTo(new Scalar(120, 255, 255));
rgbaMat4Mask.copyTo(newMatwithMaskFinished, newMat4Mask);
Highgui.imwrite("/mnt/sdcard/DCIM/newMatwithMaskFinished.bmp", newMatwithMaskFinished);//check*/
}
Your newMatwithMaskFinished should have the same size as rgbaMat4Mask and newMat4Mask.
Mat newMatwithMaskFinished = new Mat(rgbaMat4Mask.rows(), rgbaMat4Mask.cols(), CvType.CV_8UC3);
If you want to have a Mat of the bigger circle only, with transparent background, then you need to:
1) create newMatwithMaskFinished with type CV_8UC4
Mat newMatwithMaskFinished = new Mat(rgbaMat4Mask.rows(), rgbaMat4Mask.cols(), CvType.CV_8UC4);
2) set a transparent background:
newMatwithMaskFinished.setTo(new Scalar(0, 0, 0, 0));
3) Compute the bounding box box of the contour you're interested in, with boundingRect.
4) Convert rgbaMat4Mask to 4 channels (unless it's already), with cvtColor(..., COLOR_BGR2BGRA), let's call this rgba
5) Copy rgba to newMatwithMaskFinished, with mask newMat4Mask.
6) Crop newMatwithMaskFinished on box, using submat method
Using OpenCV4Android, how can I get the HSV channels of the first pixel of the masked region in a masked image (dilatedMat in the following snippet)? I know that we'd get the HSV channel values of first pixel by hsvMat.get(0,0) but I don't know how to apply this to the masked region only, rather than the entire Mat.
For example, following is a function to which a camera frame is passed as an argument, and I have generated a mask, but how should I proceed from there?
NOTE: Please keep in mind that the masked region is Not a rectangle, it has an irregular shape.
private void detectColoredBlob (Mat rgbaFrame) {
Mat hsvImage = new Mat();
Imgproc.cvtColor(rgbaFrame, hsvImage, Imgproc.COLOR_RGB2HSV_FULL);
Mat maskedImage = new Mat();
Scalar lowerThreshold = new Scalar(85, 50, 20);
Scalar upperThreshold = new Scalar(135, 255, 77);
Core.inRange(hsvImage, lowerThreshold, upperThreshold, maskedImage);
Mat dilatedMat= new Mat();
Imgproc.dilate(maskedImage, dilatedMat, new Mat() );
//****************WHAT NOW???**************
}