How to draw a minimum enclosing circle around a contour in EmguCV?. FindContours() method returns a set of points. But to draw the circle it asks for pointf. Is there a work around this? Thanks.
Yes there is a way. You will just have to convert the Contour into an array of PointF like this:
for (var contour = binaryImage.FindContours(CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE,
RETR_TYPE.CV_RETR_CCOMP, mem);
contour != null;
contour = contour.HNext)
{
//assuming you have a way of getting the index of
//point you wanted to extract from the current contour
var index = 0;
PointF[] pointfs = Array.ConvertAll(contour.ToArray(),
input => new PointF(input.X, input.Y));
//just an example
var circle = new CircleF(pointfs[index], 2.0f);
}
Related
I am using following functions to detect images. However, it detects thousands of circles instead of 16. How can I make sure it only detects what I see? Changing Radius or Relative intensity do not make any difference.
The images I used is this :
Bitmap ImageBitmap = (Bitmap)pictureBox1.Image;
var filter = new FiltersSequence(new IFilter[]
{
Grayscale.CommonAlgorithms.BT709,
new Threshold(0x40)
});
var binaryImage = filter.Apply(ImageBitmap);
// for (int i = 0; i < 10000; i++)
{
// System.Drawing.Image image = System.Drawing.Image.FromFile(imagePath);
// GrayBMP_File.CreateGrayBitmapFile(image, "c:/path/to/8bpp/image.bmp");
// Bitmap ImageBitmap = Convert.Gra ImageBitmap.Con
HoughCircleTransformation circleTransform = new HoughCircleTransformation(50);
// apply Hough circle transform
circleTransform.ProcessImage(binaryImage);
Bitmap houghCirlceImage = circleTransform.ToBitmap();
// get circles using relative intensity
HoughCircle[] circles = circleTransform.GetCirclesByRelativeIntensity(0.9);
int numCircles = circleTransform.CirclesCount;
label1.Text = numCircles.ToString();
pictureBox1.Image = houghCirlceImage;
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(ImageBitmap);
foreach (HoughCircle circle in circles)
{
g.DrawEllipse(Pens.Green, circle.X, circle.Y, 10,10);
}
pictureBox1.Image = ImageBitmap;
// ImageBitmap.Dispose();
// binaryImage.Dispose();
}
Try this python solution from here:
import cv2
import numpy as np
img = cv2.imread('test.jpg',0)
cimg = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)
circles = cv2.HoughCircles(img,cv2.HOUGH_GRADIENT,1,20,
param1=50,param2=30,minRadius=0,maxRadius=0)
circles = np.uint16(np.around(circles))
d=1
for i in circles[0,:]:
# draw the outer circle
cv2.circle(cimg,(i[0],i[1]),i[2],(0,255,0),2)
# draw the center of the circle
cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3)
crop_img=img[i[0]-i[2]-2:i[0]+i[2]+2,i[1]-i[2]-2:i[1]+i[2]+2]
cv2.imshow('cropped circle',crop_img)
cv2.imwrite('test_%d.png'%d,crop_img)
cv2.waitKey(0)
d+=1
cv2.imshow('detected circles',cimg)
print(len(circles[0,:]))
cv2.waitKey(0)
cv2.destroyAllWindows()
OUTPUT:
16
I'm working on a lane detection problem using OpenCV in C++. To select the ROI, I'm planning to use a trapezium shape mask to filter the region. However, I'm unable to figure out how to draw a trapezium. After choosing the four vertices, a differently shaped polygon is being drawn. Here's my code.
void select_roi(Mat &frame){
int rows = frame.rows;
int cols = frame.cols;
Point points[1][4];
points[0][0] = Point(cols*0.05, rows);
points[0][1] = Point(cols*0.4, rows*0.4);
points[0][2] = Point(cols*0.95, rows);
points[0][3] = Point(cols*0.6, rows*0.4);
Mat img = empty_image(frame); //User defined function that returns empty image of frame dimensions
const Point* ppt[1] = {points[0]};
int npt[] = {4};
fillPoly(img, ppt, npt, 1, Scalar(255,0,0), 8);
imshow("Poly",img);
}
Really simple error: your points are not in the right order. Currently you're drawing the bottom left, then the top left, then the bottom right, and then the top right, and connecting back to the first. Imagine if you traced it out with those coordinates in order---you'd get the same shape that you have in error. So all you need to do is order them so that if you drew lines from each point to the next, you'd create the shape.
points[0][0] = Point(cols*0.05, rows);
points[0][1] = Point(cols*0.4, rows*0.4);
points[0][2] = Point(cols*0.6, rows*0.4);
points[0][3] = Point(cols*0.95, rows);
I'm trying to achieve this kind of shadow, my research led me to using the CGPathRefto draw the shadow myself, but I can't figure out how it actually works.
Drawing the label.layer.shadowPath looks like a good plan, can anyone show me/point me to how I should proceed?
EDIT : I'm now to the point of trying to draw a UIBezierPath based on the string in the current label, the path being the actual shape of the shadow I need. I'm not sure that's the best option but it looks more promising.
EDIT 2 : Here is the code i'm now working with. this outlines the text of the label as an image, but it's pretty much the exact same text as the label itself, i still have to work my way around making it look like a shadow. Note, we're using Xamarin
public override void Draw (CoreGraphics.CGRect rect)
{
base.Draw (rect);
using (CGContext g = UIGraphics.GetCurrentContext ()) {
UIBezierPath completePath = UIBezierPath.Create ();
g.ScaleCTM (1, -1);
g.TranslateCTM (2, -(this.Bounds.Height / 2) - (this.Font.LineHeight / 3));
CTLine line = new CTLine (this.AttributedText);
CTRun[] runs = line.GetGlyphRuns ();
for (int i = 0; i < runs.Length; i++) {
CTRun run = runs [i];
CTFont font = run.GetAttributes ().Font;
for (int j = 0; j < run.GlyphCount; j++) {
NSRange currentRange = new NSRange (j, 1);
CGPoint[] positions = run.GetPositions (currentRange);
ushort[] glyphs = run.GetGlyphs (currentRange);
CGPath letter = font.GetPathForGlyph (glyphs [0]);
CGAffineTransform transform = CGAffineTransform.MakeTranslation (positions [0].X, positions [0].Y);
CGPath path = new CGPath (letter, transform);
UIBezierPath newPath = UIBezierPath.FromPath (path);
completePath.AppendPath (newPath);
}
}
completePath.LineWidth = 1;
UIColor.Red.SetStroke ();
UIColor.Blue.SetFill ();
completePath.Stroke ();
completePath.Fill ();
completePath.ClosePath ();
//Here I will try to loop over my current points and go down & right at every step of the loop, see how it goes performance-wise. Instead of one complex drawing I'll just have a very simple drawing that has thousands of points :o
g.AddPath (completePath.CGPath);
g.DrawPath (CGPathDrawingMode.FillStroke);
}
There is no built in way to achieve this effect. You have to implement the drawing code on your own.
Here are two ideas to create the shadow:
Draw the text in dark blue color, repeated n times, starting from the original position in 0.5 pt. steps shifted down right. This has bad performance but is really easy to implement.
Find the text outline using Core Text and implement some algorithm that creates the actual outline of the shadow. This could then be used as the shadowPath property.
I am new to EMGU.CV and I am struggling a bit. Let me start by giving some background of the project, i am trying to track a users fingers, i.e. calculate the users finger tips, but i am struggling a bit. I have created a set of code which filters the depth information to only a certain range and I generate a Bitmap image, tempBitmap, i then convert this image to a greyscale image using EMGU.CV which can be used by cvCanny. Once this is done i apply dilate filter to the canny image to thicken up the outline of the hand to better improve the chance of generating a successful contour, I then try to get the contours of the hand. Now what i have managed to do is to draw a box around the hand, but i am struggling to find a way to convert the contours generated by FindContours to a set of Points i can use to draw the contour with. the variable depthImage2 is a Bitmap image variable i use to draw on before assinging it to the picturebox variable on my C# form based application. any information or guidance you can provide me with will be greatly appreciated, also if my code isnt correct maybe guiding me in a direction where i can calculate the finger tips. I think i am almost there i am just missing something, so any help of any kind will be appreciated.
Image<Bgr, Byte> currentFrame = new Image<Bgr, Byte>(tempBitmap);
Image<Gray, Byte> grayImage = currentFrame.Convert<Gray, Byte>().PyrDown().PyrUp();
Image<Gray, Byte> cannyImage = new Image<Gray, Byte>(grayImage.Size);
CvInvoke.cvCanny(grayImage, cannyImage, 10, 60, 3);
StructuringElementEx kernel = new StructuringElementEx(
3, 3, 1, 1, Emgu.CV.CvEnum.CV_ELEMENT_SHAPE.CV_SHAPE_ELLIPSE);
CvInvoke.cvDilate(cannyImage, cannyImage, kernel, 1);
IntPtr cont = IntPtr.Zero;
Graphics graphicsBitmap = Graphics.FromImage(depthImage2);
using (MemStorage storage = new MemStorage()) //allocate storage for contour approximation
for (Contour<Point> contours =
cannyImage.FindContours(Emgu.CV.CvEnum.CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE,
Emgu.CV.CvEnum.RETR_TYPE.CV_RETR_EXTERNAL);
contours != null; contours = contours.HNext)
{
IntPtr seq = CvInvoke.cvConvexHull2(contours, storage.Ptr, Emgu.CV.CvEnum.ORIENTATION.CV_CLOCKWISE, 0);
IntPtr defects = CvInvoke.cvConvexityDefects(contours, seq, storage);
Seq<Point> tr = contours.GetConvexHull(Emgu.CV.CvEnum.ORIENTATION.CV_CLOCKWISE);
Seq<Emgu.CV.Structure.MCvConvexityDefect> te = contours.GetConvexityDefacts(
storage, Emgu.CV.CvEnum.ORIENTATION.CV_CLOCKWISE);
graphicsBitmap.DrawRectangle(
new Pen(new SolidBrush(Color.Red)), tr.BoundingRectangle);
}
Contour contours = cannyImage.FindContours(Emgu.CV.CvEnum.CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_NONE) //to return all points
then:
List<Point[]> convertedContours = new List<Point[]>();
while(cotours!=null)
{
var contourPoints = contours.ToArray(); //put Seq<Point> to Point[], ToList() is also available ?
convertedContours.Add(contourpoints);
contours = contours.HNext;
}
you can draw contour by image Draw functon overload.
just find signature that contains parameter Seq<>
....
After some color detection and binary thresholding, I use the following code to find the contours and draw them onto the image:
using (MemStorage stor = new MemStorage())
{
Contour<Point> contours = img.FindContours(
Emgu.CV.CvEnum.CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE,
Emgu.CV.CvEnum.RETR_TYPE.CV_RETR_LIST,
stor);
for (; contours != null; contours = contours.HNext)
{
Contour<Point> currentContour = contours.ApproxPoly(contours.Perimeter * poly, stor);
img.Draw(currentContour,new Bgr(255,255,255),1);
Rectangle currentrect = currentContour.BoundingRectangle;
img.Draw(currentrect,new Bgr(255,255,255),2);
}
}
My problem is, as I expected, that if the contour is a rectangle but is rotated in the image, the bounding rectangle does not change its orientation to fit the rotation. Is their another way to accomplish this function? Any help would be greatly appreciated.
Yes, there is another way to accomplish this. You can use
contour.GetConvexHull(ORIENTATION.CV_CLOCKWISE);
using Moments, you can easily get the orientation and adjust the rectangle accordingly.
The method you are looking for is:
PointCollection.MinAreaRect(points);
Worked example is here:
http://www.emgu.com/wiki/index.php/Minimum_Area_Rectangle_in_CSharp
Complete documentation (which has little more than the above) is located here:
http://www.emgu.com/wiki/files/2.4.0/document/html/0d5fd148-0afb-fdbf-e995-6dace8c8848d.htm