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
Related
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.
> 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
I'm trying to get the red rectangle region below "C", as image below:
And below is my source code use Opencv4Android:
public void threshold() {
Mat rgbMat = new Mat();
Mat grayMat = new Mat();
Mat edgeMat = new Mat();
Utils.bitmapToMat(bmp, rgbMat);
Mat intermediate = new Mat();
Imgproc.cvtColor(rgbMat, intermediate, Imgproc.COLOR_BGR2GRAY);
Imgproc.GaussianBlur(intermediate, intermediate, new Size(3, 3), 0);
Imgproc.threshold(intermediate, intermediate, 190, 255, Imgproc.THRESH_BINARY | Imgproc.THRESH_OTSU);
Imgproc.Canny(intermediate, intermediate, 60, 140);
List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
Mat mHierarchy = new Mat();
Imgproc.findContours(intermediate, contours, mHierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
Scalar CONTOUR_COLOR = new Scalar(255,0,0,255);
Log.e(TAG, "Contours count: " + contours.size());
Imgproc.drawContours(intermediate, contours, -1, CONTOUR_COLOR);
Bitmap edgeBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), Config.ARGB_8888);
Utils.matToBitmap(intermediate, edgeBmp);
imageView.setImageBitmap(edgeBmp);
}
but the result is not as I expected: as image below:
As log show, Contours count: 372, and the rectangle region is discontinuous, How can I get the contour of the red rectangle region, and filter another useless region. I have referenced some other questions, but the question still not be solved, Could you do me a favor?
[update] change the code by the suggest from Morotspaj,
public void thresholdNew() {
Mat rgbMat = new Mat();
Mat grayMat = new Mat();
Utils.bitmapToMat(bmp, rgbMat);
Imgproc.cvtColor(rgbMat, grayMat, Imgproc.COLOR_BGR2GRAY);
Vector<Mat> bgr_planes = new Vector<Mat>();
Core.split(rgbMat, bgr_planes);
Mat redMat = bgr_planes.get(2);
Mat redness = new Mat();
Core.subtract(redMat, grayMat, redness);
Mat intermediateMat1 = new Mat();
Mat intermediateMat2 = new Mat();
Imgproc.GaussianBlur(redness, intermediateMat1, new Size(15,15), 0);
Imgproc.GaussianBlur(redness, intermediateMat2, new Size(55,55), 0);
Mat red_mask = new Mat();
Core.subtract(intermediateMat1, intermediateMat2, red_mask );
Imgproc.threshold(red_mask , red_mask , 90, 255, Imgproc.THRESH_BINARY | Imgproc.THRESH_OTSU);
Mat masked_image = rgbMat.clone();
masked_image = masked_image.setTo(new Scalar(255,0,0), red_mask );
Bitmap edgeBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), Config.ARGB_8888);
Utils.matToBitmap(masked_image, edgeBmp);
imageView.setImageBitmap(edgeBmp);
}
But the result is not as I expected and different with Morotspaj's.
Any error exist in the above code?
[update] Sorry, I am very busy these days, I will be try again later, and If I can not implement with Java, I will use Morotspaj's code through JNI. I will be update soon.
I made a filter to mask out the red rectangle region, just for you ;)
Mat rgbMat = imread("red_rectangle.jpg", -1);
Mat grayMat;
cvtColor(rgbMat, grayMat, COLOR_BGR2GRAY);
// Separate the red channel and compare it to the gray image
Mat channels[3];
split(rgbMat, channels);
Mat redness = Mat_<float>(channels[2]) - Mat_<float>(grayMat);
// Find the sharp red region
Mat red_blur1;
Mat red_blur2;
GaussianBlur(redness, red_blur1, Size(15,15), 0);
GaussianBlur(redness, red_blur2, Size(55,55), 0);
Mat red_mask = (red_blur1-red_blur2) > 2;
// Store result
Mat masked_image = rgbMat.clone();
masked_image.setTo(Scalar(0,0,255), red_mask);
imwrite("red_mask.png", red_mask);
imwrite("masked_image.png", masked_image);
The GaussianBlur method calls can be replaced by boxFilter if you need better performance, and the constants here and there can of course be tweaked. Hope this helps!
EDIT: Taking the difference of two differently blurred images is known as Difference of Gaussians (DoG). It finds changes in a certain scale depending on the size of the kernels. The smaller kernel is used to smooth away small details and noise. The bigger kernel destroys the details we are interested in but not the regions with very smooth changes that we don't want. By taking the difference between them we end up with only the details in the scale we are interested in! A mask can then be created easily by thresholding with the > operator.
i have code to load image from sdcard and post it to ImageView.
Mat mRgba = Highgui.imread(dir);
Bitmap bmp = Bitmap.createBitmap(mRgba.cols(), mRgba.rows(),Bitmap.Config.ARGB_8888);
Utils.matToBitmap(mRgba, bmp);
mImage.setImageBitmap(bmp, true, null, 5.0f);
the image is loaded but it's wrong color. Color seem to be inverted (but not inverted).
Here is image comparison
I tried to load image by
Bitmap bmp = BitmapFactory.decodeFile(dir);
It worked correctly. But i have to use Highgui.imread.
What wrong with my code?
You will have to use something like this:
Mat inputImage = Highgui.imread(pathToFile);
Mat tmp = new Mat();
Imgproc.cvtColor(inputImage, tmp, Imgproc.COLOR_BGR2RGB);
Bitmap imageToShow = Bitmap.createBitmap(tmp.cols(), tmp.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(tmp, imageToShow);
You're trying to load a bitmap supposing that the image is 8-bit/color RGBA: are you sure of that?
Also note that ARGB is not RGBA. You may need to re-arrange the bytes of each pixel. Something like
int pixel = get_the_pixel();
int alpha = 0xff & pixel;
pixel = pixel<<8 | alpha;
set_the_pixel(pixel);
You'll want to do something more efficient than accessor methods shown here, but you get the idea.