opencv를 사용하여 이미지에서 파란색을 감지하려고 시도하고 예기치 않은 결과를 얻습니다. (Trying to detect blue color from image using opencv, and getting unexpected result)

내가 놓치거나 잘못하고 있는 것은 무엇인가요? strong>

코드:

private void detectColoredBlob () { 
        Highgui.imwrite("/mnt/sdcard/DCIM/rgbaFrame.jpg", rgbaFrame);//check
        Mat hsvImage = new Mat(); 
        Imgproc.cvtColor(rgbaFrame, hsvImage, Imgproc.COLOR_RGB2HSV_FULL);
        Highgui.imwrite("/mnt/sdcard/DCIM/hsvImage.jpg", hsvImage);//check

        Mat maskedImage = new Mat(); 
        Scalar lowerThreshold = new Scalar(170, 0, 0); 
        Scalar upperThreshold = new Scalar(270, 255, 255); 
        Core.inRange(hsvImage, lowerThreshold, upperThreshold, maskedImage);
        Highgui.imwrite("/mnt/sdcard/DCIM/maskedImage.jpg", maskedImage);//check

        Mat dilatedMat= new Mat(); 
        Imgproc.dilate(maskedImage, dilatedMat, new Mat() ); 
        Highgui.imwrite("/mnt/sdcard/DCIM/dilatedMat.jpg", dilatedMat);//check
        List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
        Imgproc.findContours(dilatedMat, contours, new Mat(), Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);
        //Use only the largest contour. Other contours (any other possible blobs of this color range) will be ignored.
        MatOfPoint largestContour = contours.get(0);
        double largestContourArea = Imgproc.contourArea(largestContour);
        for ( int i=1; i<contours.size(); ++i) {//NB Notice the prefix increment.
            MatOfPoint currentContour = contours.get(0);
            double currentContourArea = Imgproc.contourArea(currentContour);
            if (currentContourArea > largestContourArea) {
                largestContourArea = currentContourArea;
                largestContour = currentContour;
            }
        }

        Rect detectedBlobRoi = Imgproc.boundingRect(largestContour);
        Mat detectedBlobRgba = rgbaFrame.submat(detectedBlobRoi);
        Highgui.imwrite("/mnt/sdcard/DCIM/detectedBlobRgba.jpg", detectedBlobRgba);//check
     }

1. 컴퓨터에 있는 원본 이미지 노트북 화면.

1. rgbaFrame.jpg

int xOffset = (openCvCameraBridge.getWidth() ‑ cols) / 2;
int yOffset = (openCvCameraBridge.getHeight() ‑ rows) / 2;

int x = (int) motionEvent.getX() ‑ xOffset;
int y = (int) motionEvent.getY() ‑ yOffset;

Log.i(TAG, "Touch image coordinates: (" + x + ", " + y + ")");//check

if ((x < 0) || (y < 0) || (x > cols) || (y > rows)) { return false; }

Rect touchedRect = new Rect();
touchedRect.x = (x > 4) ? x ‑ 4 : 0;
touchedRect.y = (y > 4) ? y ‑ 4 : 0;
touchedRect.width = (x + 4 < cols) ? x + 4 ‑ touchedRect.x : cols ‑ touchedRect.x;
touchedRect.height = (y + 4 < rows) ? y + 4 ‑ touchedRect.y : rows ‑ touchedRect.y;
Mat touchedRegionRgba = rgbaFrame.submat(touchedRect);

Mat touchedRegionHsv = new Mat();
Imgproc.cvtColor(touchedRegionRgba, touchedRegionHsv, Imgproc.COLOR_RGB2HSV_FULL);

double[] channelsDoubleArray = touchedRegionHsv.get(0, 0);//**********
float[] channelsFloatArrayScaled = new float[3];
for (int i = 0; i < channelsDoubleArray.length; i++) {
    if (i == 0) {
        channelsFloatArrayScaled[i] = ((float) channelsDoubleArray[i]) * 2;// TODO Wrap an ArrayIndexOutOfBoundsException wrapper
    } else if (i == 1 || i == 2) {
        channelsFloatArrayScaled[i] = ((float) channelsDoubleArray[i]) / 255;// TODO Wrap an ArrayIndexOutOfBoundsException wrapper
    }
}

int androidColor = Color.HSVToColor(channelsFloatArrayScaled);

view.setBackgroundColor(androidColor);
textView.setText("Hue : " + channelsDoubleArray[0] + "\nSaturation : " + channelsDoubleArray[1] + "\nValue : "
        + channelsDoubleArray[2]);

touchedRegionHsv.release();
return false; // don't need subsequent touch events 

}

---

참조 솔루션

방법 1:

Probably the range you are using is wrong for blue, In OpenCV the hue range is from 0‑180 and you have given it's 170‑270. Find the correct hue value for blue and use in inRange.

1. http://answers.opencv.org/question/30547/need‑to‑know‑the‑hsv‑value/#30564
2. http://answers.opencv.org/question/28899/correct‑hsv‑inrange‑values‑for‑red‑objects/#28901

You can refer the answer here for choosing correct hsv value.

Below is the code for segmenting red color, check it with your code, and make sure it segmenting red object.

    Imgproc.cvtColor(rgbaFrame, hsv, Imgproc.COLOR_RGB2HSV,4); // Convert to hsv for color segmentation.      
    Core.inRange(hsv,new Scalar(0,50,40,0), new Scalar(10,255,255,0),thr);//upper red range of hue cylinder 

방법 2:

There are multiple traps in converting an image to HSV color space and using HSV color space.

1. OpenCV uses a compressed hue range because original, hue ranges from 0 to 360 which means that the values can't fit in 1 byte (values 0 to 255) while saturation and value channels are exactly covered by 1 byte. Therefore, OpenCV uses hue values divided by 2. So the hue channel will be covered by matrix entries between 0 and 180. Regarding this, your hue range from 170 to 270 should be divided by 2 = range 65 to 135 in OpenCV.

2. hue tells you about the color tone, but saturation and value are still important to reduce noise, so set your threshold to some minimum saturation and value, too

3. very important: OpenCV uses BGR memory ordering for rendering and image saving. This means that if your image has RGB(a) ordering and you save it without color conversion, you swap R and B channels, so assumed red color will become blue etc. Unfortunately normally you can't read from the image data itself, whether it is RGB or BGR ordered, so you should try to find it out from the image source. OpenCV allows several flags to convert either from RGB(A) to HSV and/or from BGR(A) to HSV, and/or from RGB to BGR etc, so that is no problem, as long as you know which memory format your image uses. However, displaying and saving always assumes BGR ordering, so if you want to display or save the image, convert it to BGR! HSV values however will be the same, no matter whether you convert a BGR image with BGR2HSV or whether you convert a RGB image with RGB2HSV. But it will have wrong values if you convert a BGR image with RGB2HSV or a RGB image with BGR2HSV... I'm not 100% sure about Java/Python/Android APIs of openCV, but your image really looks like B and R channels are swapped or misinterpreted (but since you use RGBA2HSV conversion that's no problem for the hsv colors).

about your contour extraction, there is a tiny (copy paste?) bug in your code that everyone might observe once in a while:

MatOfPoint largestContour = contours.get(0);
    double largestContourArea = Imgproc.contourArea(largestContour);
    for ( int i=1; i<contours.size(); ++i) {//NB Notice the prefix increment.
        // HERE you had MatOfPoint currentContour = contours.get(0); so you tested the first contour in each iteration
        MatOfPoint currentContour = contours.get(i);
        double currentContourArea = Imgproc.contourArea(currentContour);
        if (currentContourArea > largestContourArea) {
            largestContourArea = currentContourArea;
            largestContour = currentContour;
        }
    }

so probably just this has to be changed to use i instead of 0 in the loop

MatOfPoint currentContour = contours.get(i);

(by Solace、Haris、Micka)

참조 문서

1. Trying to detect blue color from image using opencv, and getting unexpected result (CC BY‑SA 2.5/3.0/4.0)