I am able to detect the Contour in an image using C++. However, I want to convert it in Android using java lang. So, i make it using android studio.
(partly because I am a JAVA newbie)
Then i found some problems, When i run it, i had a error problems with this code :
if(contours[contourIdx].size()>100)
in this main program.
#Override
public void onCameraViewStarted(int width, int height) {
mRgba = new Mat(height, width, CvType.CV_8UC4);
mHsv = new Mat(height,width,CvType.CV_8UC3);
hierarchy = new Mat();
mHsvMask = new Mat();
mDilated = new Mat(height, width, CvType.CV_8UC4);
}
#Override
public void onCameraViewStopped() {
mRgba.release();
mHsv.release();
mHsvMask.release();
mDilated.release();
hierarchy.release();
}
#Override
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
mRgba =inputFrame.rgba();
mHsv = new Mat();
Imgproc.cvtColor(mRgba, mHsv, Imgproc.COLOR_RGB2HSV, 3);
hierarchy.release();
Scalar lowerThreshold = new Scalar ( 120, 100, 100 );
Scalar upperThreshold = new Scalar ( 179, 255, 255 );
Core.inRange ( mHsv, lowerThreshold , upperThreshold, mHsvMask );
Imgproc.dilate ( mHsvMask, mDilated, new Mat() );
Imgproc.findContours(mDilated, contours, hierarchy, Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);
for ( int contourIdx=0; contourIdx < contours.size(); contourIdx++ )
{
if(contours[contourIdx].size()>100) // Minimum size allowed for consideration
{
Imgproc.drawContours ( mRgba, contours, contourIdx, new Scalar(0,255,0) , -5);
}
}
return mRgba;
}
}
Hopefully, someone has some experience in this. Thanks..
Use the area concept
if(Imgproc.contourArea(contours.get(contourIdx))>100) {
Imgproc.drawContours(mRgba, contours, contourIdx, new Scalar(Math.random() * 255, Math.random() * 255, Math.random() * 255), 1, 8, hierarchy, 0, new Point());
}
Related
I am trying to determine a way to change the pixel color of my masks from black to a different color. Unfortunately, I have not be able to determine a way to do this task. Essentially, what I am trying to do is take this image:
and convert the black portions to a color with values (255, 160, 130). I have tried several methods to try and achieve my goal. These include draw contours, setTo, and looping through the matrix. Unfortunately all of these attempts have failed. I have included the code and the resulting outcomes below.
Draw Contours method
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
Mat img = Imgcodecs.imread(
"C:\\Users\\Hassan\\Documents\\School\\Me\\COMP5900 Y\\Project\\Project\\src\\resources\\face.jpg");
Mat img_grey = new Mat();
Mat grad = new Mat(), grad_x = new Mat(), grad_y = new Mat();
Mat abs_grad_x = new Mat(), abs_grad_y = new Mat();
int ddepth = CvType.CV_32F;
int scale = 1;
int delta = 0;
Imgproc.GaussianBlur(img, img, new Size(3, 3), 0, 0, Core.BORDER_CONSTANT);
Imgproc.cvtColor(img, img_grey, Imgproc.COLOR_BGR2GRAY);
// Apply Sobel
Imgproc.Sobel(img_grey, grad_x, ddepth, 1, 0, 3, scale, delta, Core.BORDER_DEFAULT);
Imgproc.Sobel(img_grey, grad_y, ddepth, 0, 1, 3, scale, delta, Core.BORDER_DEFAULT);
// converting back to CV_8U
Core.convertScaleAbs(grad_x, abs_grad_x);
Core.convertScaleAbs(grad_y, abs_grad_y);
// Total Gradient (approximate)
Core.addWeighted(abs_grad_x, 0.5, abs_grad_y, 0.5, 0, grad);
Photo.fastNlMeansDenoising(grad, grad);
Imgproc.GaussianBlur(grad, grad, new Size(3, 3), 0, 0, Core.BORDER_CONSTANT);
// isolate background
Mat background = new Mat();
Imgproc.threshold(grad, background, 2, 255, Imgproc.THRESH_BINARY);
// draw contours
List<MatOfPoint> contours = new ArrayList<>();
Mat hierarchy = new Mat();
Imgproc.findContours(background, contours, hierarchy, Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_NONE);
Mat drawing = Mat.zeros(background.size(), CvType.CV_8UC3);
List<MatOfPoint> hullList = new ArrayList<>();
for (MatOfPoint contour : contours) {
MatOfInt hull = new MatOfInt();
Imgproc.convexHull(contour, hull);
Point[] contourArray = contour.toArray();
Point[] hullPoints = new Point[hull.rows()];
List<Integer> hullContourIdxList = hull.toList();
for (int i = 0; i < hullContourIdxList.size(); i++) {
hullPoints[i] = contourArray[hullContourIdxList.get(i)];
}
hullList.add(new MatOfPoint(hullPoints));
}
for (int i = 0; i < contours.size(); i++) {
Scalar color = new Scalar(255, 160, 130);
Imgproc.drawContours(drawing, contours, i, color);
//Imgproc.drawContours(drawing, hullList, i, color );
}
Note here, that I also tried using Imgproc.RETR_EXTERNAL as well, but that produced a completely black image. Also the name of the HighGui window is called "flood fill", but I just forgot to update the name.
setTo
// replace find and draw contours portion of code above
Mat out = new Mat();
background.copyTo(out);
out.setTo(new Scalar(255, 160, 130), background);
Iterating through matrix
// replace draw contours portion of code above
for (a = 0; a < background.rows(); a++) {
for(b = 0; b < background.cols(); b++) {
if(background.get(a,b)[0] == 0) {
//background.put(a, b, CvType.CV_16F, new Scalar(255, 160, 130));
double[] data = {255, 160, 130};
background.put(a, b, data);
}
}
}
The loop is promising, but I know it will not be efficient as I have 2 other masks that I would like to update as well. Could you please suggest an efficient method, that allows me to set the value for all three channels?
Thanks
I am not sure why you are doing many operations on the image but to me it looks like applying the mask and replacing the color efficiently. So if there are other complexities than please let me know.
Below is the code I was looking for in Java.
public static void main(String s[]) {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
Mat matr =Imgcodecs.imread("/home/shariq/Desktop/test.png");
Mat result = new Mat();
//create a mask based on range
Core.inRange(matr, new Scalar(0), new Scalar(50), result);
Imgcodecs.imwrite("/home/shariq/Desktop/test_in.png", result);
//apply the mask with color you are looking for, note here scalar is in hsv
matr.setTo(new Scalar(130,160,255),result);
Imgcodecs.imwrite("/home/shariq/Desktop/result.png", matr);
}
We are creating a mask for the pixel values between 0-50 for black color using inRange method.
Core.inRange(matr, new Scalar(0), new Scalar(50), result);
This mask in result variable is than applied to original matrix using setTo method. The replacement color value is provided in HSV format through Scalar object. new Scalar(a,b,c) in HSV can be understand in RGB like this Red = c, Green = b and Blue = a.
matr.setTo(new Scalar(130,160,255),result);
Its quite fast compared to iterating the pixels one by one.
I am trying to scan a MTG card using OpenCV on android. I have it to where I can detect the edges of the card and even draw an outline around it but am confused on how to extract just the card from the background and then exit from the camera preview. Here is my code so far:
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
Mat result = new Mat();
Mat mask = new Mat();
List<MatOfPoint> contours = new ArrayList<>();
Mat hierarchy = new Mat();
mRgba = inputFrame.rgba();
Imgproc.Canny(mRgba, result, 40, 120);
Imgproc.GaussianBlur(result, result, new Size(9,9), 2, 2);
Imgproc.findContours(result, contours, hierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE, new Point(0,0));
Imgproc.drawContours(mask, contours, -1, new Scalar(0, 255, 0), 1);
hierarchy.release();
for ( int contourIdx=0; contourIdx < contours.size(); contourIdx++ )
{
// Minimum size allowed for consideration
MatOfPoint2f approxCurve = new MatOfPoint2f();
MatOfPoint2f contour2f = new MatOfPoint2f( contours.get(contourIdx).toArray() );
//Processing on mMOP2f1 which is in type MatOfPoint2f
double approxDistance = Imgproc.arcLength(contour2f, true)*0.02;
Imgproc.approxPolyDP(contour2f, approxCurve, approxDistance, true);
//Convert back to MatOfPoint
MatOfPoint points = new MatOfPoint( approxCurve.toArray() );
// Get bounding rect of contour
Rect rect = Imgproc.boundingRect(points);
Imgproc.rectangle(mRgba, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(255, 0, 0, 255), 3);
}
Bitmap card = Bitmap.createBitmap(result.cols(), result.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(result, card);
return mRgba;
}
}
Here is an example of what it looks like when run the code. As you can see the card is outlined by a red rectangle now but how do I extract just whats in the rectangle, save it to a mat or bitmap and then exit the camera?
screenshot of outlined card
I didn't test it, but can't you just use...
return new Mat(mRgba, rect);
I have used find contours and boundingrect and display it at my project. then I want to find the largest contours and display it. Is this possible? I am newbie to OpenCV java lang.
heres my code so far:
#Override
public void onCameraViewStarted(int width, int height) {
mRgba = new Mat(height, width, CvType.CV_8UC4);
mHsv = new Mat(height,width,CvType.CV_8UC3);
hierarchy = new Mat();
mHsvMask = new Mat();
mDilated = new Mat();
mEroded = new Mat();
}
#Override
public void onCameraViewStopped() {
mRgba.release();
mHsv.release();
mHsvMask.release();
mDilated.release();
hierarchy.release();
}
#Override
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
mRgba =inputFrame.rgba();
contours = new ArrayList<MatOfPoint>();
hierarchy =new Mat();
mHsv = new Mat();
mHsvMask =new Mat();
Imgproc.cvtColor(mRgba, mHsv, Imgproc.COLOR_RGB2HSV);
Scalar lowerThreshold = new Scalar ( 0, 0, 0 ); // Blue color – lower hsv values
Scalar upperThreshold = new Scalar ( 179, 255, 10 ); // Blue color – higher hsv values
Core.inRange ( mHsv, lowerThreshold , upperThreshold, mHsvMask );
//just some filter
//Imgproc.dilate ( mHsvMask, mDilated, new Mat() );
//Imgproc.erode(mDilated,mEroded,new Mat());
Imgproc.findContours(mHsvMask, contours, hierarchy, Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_SIMPLE);
for ( int contourIdx=0; contourIdx < contours.size(); contourIdx++ )
{
//Minimun size allowed for consideration
MatOfPoint2f approxCurve = new MatOfPoint2f();
MatOfPoint2f contour2f = new MatOfPoint2f(contours.get(contourIdx).toArray());
//Processing on mMOP2f1 which is in type MatOfPoint2f
double approxDistance = Imgproc.arcLength(contour2f,true)*0.02;
Imgproc.approxPolyDP(contour2f,approxCurve,approxDistance,true);
//convert to MatofPoint
MatOfPoint point = new MatOfPoint(approxCurve.toArray());
//get boundingrect from contour
Rect rect = Imgproc.boundingRect(point);
Imgproc.rectangle(mRgba,new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(255, 0, 0, 255),3);
//bisa Imgproc.rectangle(mRgba, rect.tl(), rect.br(), new Scalar(255, 0, 0),1, 8,0);
//show contour kontur
if(Imgproc.contourArea(contours.get(contourIdx))>100) {
Imgproc.drawContours(mRgba, contours, contourIdx, new Scalar(0,255,0), 5);
}
}
return mRgba;
Hopefully, someone has some experience in this. Thanks..
With function Imgproc.contourArea you can just simply find the areas of all of your contours and the contour with the largest area would simply be the largest one.
Code to draw the largest contour would be like this:
double maxVal = 0;
int maxValIdx = 0;
for (int contourIdx = 0; contourIdx < contours.size(); contourIdx++)
{
double contourArea = Imgproc.contourArea(contours.get(contourIdx));
if (maxVal < contourArea)
{
maxVal = contourArea;
maxValIdx = contourIdx;
}
}
Imgproc.drawContours(mRgba, contours, maxValIdx, new Scalar(0,255,0), 5);
I'm new to android and my application crashes after some time when I use drawcontour. The application has to look for the largest contour and compute its bounding box. Here is a sample of my code:
public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
img_rgb = inputFrame.rgba();
Imgproc.blur(img_rgb, blur, new Size(25,25));
Imgproc.cvtColor(blur, img_gray, Imgproc.COLOR_BGR2GRAY);
Imgproc.threshold(img_gray, thres1, 0, 255, Imgproc.THRESH_OTSU);
Imgproc.erode(thres1, erode1, new Mat(), new Point(-1,-1), 3);
Imgproc.dilate(erode1, dilate1, new Mat(), new Point(-1,-1), 2);
Imgproc.erode(dilate1, erode2, new Mat(), new Point(-1,-1), 3);
Imgproc.dilate(erode2, dilate2, new Mat(), new Point(-1,-1), 2);
Imgproc.adaptiveThreshold(dilate2, thres2, 128,Imgproc.ADAPTIVE_THRESH_MEAN_C, Imgproc.THRESH_BINARY_INV,7, 1);
contours = new ArrayList<MatOfPoint>();
Imgproc.findContours(thres2, contours, hierarchy, Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_SIMPLE, new Point(0, 0));
hierarchy.release();
//Imgproc.drawContours(img_rgb, contours, -1, new Scalar(Math.random()*255, Math.random()*255, Math.random()*255));//, 2, 8, hierarchy, 0, new Point());
for(int i = 0;i<contours.size();i++){
double area = Imgproc.contourArea(contours.get(i));
if(area > largest_area){
largest_area = area;
largest_contour_index = i;
bounding_rect = Imgproc.boundingRect(contours.get(i));
}
}
Imgproc.drawContours(img_rgb,contours,largest_contour_index, new Scalar(0,255,0),2);
return img_rgb;
}
You never reset largest_area and largest_contour_index, so it may happen that largest_contour_index refers to an invalid index.
You only need to reset these values at each loop, and draw the contour only if the index is valid (i.e. if you find at least one contour). Depending on your further processing, you may want also to reset bounding_rect. You can move the boundingRect call out of the for loop, so you avoid useless computation.
Code:
// Reset values at each iteration
largest_area = 0;
largest_contour_index = -1;
for(int i = 0;i<contours.size();i++){
double area = Imgproc.contourArea(contours.get(i));
if(area > largest_area){
largest_area = area;
largest_contour_index = i;
}
}
// Draw only if index is valid
if(largest_contour_index >= 0) {
bounding_rect = Imgproc.boundingRect(contours.get(largest_contour_index));
Imgproc.drawContours(img_rgb,contours,largest_contour_index, new Scalar(0,255,0),2);
}
I'm developing a Android app to detect vehicle number plate. i did image processing up to findContours level of image. Now i need to convert following C++ code to Opencv Based Android java.
This is original image
This is after Otsu thresholding image
This is my andoid+opencv code (working 100%)
ImageView imgView = (ImageView) findViewById(R.id.imageView1);
Bitmap bmp = BitmapFactory.decodeResource(getResources(),car);
//First convert Bitmap to Mat
Mat ImageMatin = new Mat ( bmp.getHeight(), bmp.getWidth(), CvType.CV_8U, new Scalar(4));
Mat ImageMatout = new Mat ( bmp.getHeight(), bmp.getWidth(), CvType.CV_8U, new Scalar(4));
Mat ImageMatBk = new Mat ( bmp.getHeight(), bmp.getWidth(), CvType.CV_8U, new Scalar(4));
Mat ImageMatTopHat = new Mat ( bmp.getHeight(), bmp.getWidth(), CvType.CV_8U, new Scalar(4));
Mat temp = new Mat ( bmp.getHeight(), bmp.getWidth(), CvType.CV_8U, new Scalar(4));
Bitmap myBitmap32 = bmp.copy(Bitmap.Config.ARGB_8888, true);
Utils.bitmapToMat(myBitmap32, ImageMatin);
//Converting RGB to Gray.
Imgproc.cvtColor(ImageMatin, ImageMatBk, Imgproc.COLOR_RGB2GRAY,8);
Imgproc.dilate(ImageMatBk, temp, Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(9, 9)));
Imgproc.erode(temp, ImageMatTopHat, Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(9,9)));
//Core.absdiff(current, previous, difference);
Core.absdiff(ImageMatTopHat, ImageMatBk, ImageMatout);
//Sobel operator in horizontal direction.
Imgproc.Sobel(ImageMatout,ImageMatout,CvType.CV_8U,1,0,3,1,0.4,Imgproc.BORDER_DEFAULT);
//Converting GaussianBlur
Imgproc.GaussianBlur(ImageMatout, ImageMatout, new Size(5,5),2);
Imgproc.dilate(ImageMatout, ImageMatout, Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(3,3)));
Mat element = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(17, 3));
Imgproc.morphologyEx(ImageMatout, ImageMatout, Imgproc.MORPH_CLOSE, element);
//threshold image
Imgproc.threshold(ImageMatout, ImageMatout, 0, 255, Imgproc.THRESH_OTSU+Imgproc.THRESH_BINARY);
Now I need to extract number Plate
Please help me to convert following C++ code to java+opencv:.
std::vector rects;
std::vector<std::vector >::iterator itc = contours.begin();
while (itc != contours.end())
{
cv::RotatedRect mr = cv::minAreaRect(cv::Mat(*itc));
float area = fabs(cv::contourArea(*itc));
float bbArea=mr.size.width * mr.size.height;
float ratio = area/bbArea;
if( (ratio < 0.45) || (bbArea < 400) ){
itc= contours.erase(itc);
}else{
++itc;
rects.push_back(mr);
}
}
Looking at http://docs.opencv.org/java and the documentation for findContours in particular
instead of
std::vector<std::vector<cv::Point> > contours;
you will have
java.util.ArrayList<MatOfPoint> contours;
You can use contours.listIterator() to traverse the list. Something like the below (not compiled let alone run,likely to contain major blunders):
import java.util.*;
import org.opencv.imgproc.Imgproc;
import org.opencv.core.*;
/* ... */
ArrayList<RotatedRect> rects = new ArrayList<RotatedRect>()
ArrayList<MatOfPoint> contours = new ArrayList<MatOfPoint>();
Imgproc.findContours(image, contours, new Mat(), Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_NONE);
ListIterator<MatOfPoint> itc = contours.listIterator();
while(itc.hasNext())
{
MatOfPoint2f mp2f = new MatOfPoint2f(itc.next().toArray());
RotatedRect mr = Imgproc.minAreaRect(mp2f);
double area = Math.abs(Imgproc.contourArea(mp2f));
double bbArea= mr.size.area();
double ratio = area / bbArea;
if( (ratio < 0.45) || (bbArea < 400) )
{
itc.remove(); // other than deliberately making the program slow,
// does erasing the contour have any purpose?
}
else
{
rects.add(mr);
}
}