I have a Java program that works very similar to the Bezier tool in Inkscape. The purpose of my program is to allow the user to use the curves to draw a path around an object (like the head of a person) and then extract (copy) the pixels inside the enclosed curves. In the attached picture, you can see that there are 3 blue curves that form an enclosed area. I'd like to know how to copy the area enclosed by these 3 curves?
The code I use to draw the curves (I omit the red tangent lines and the red control points for simplicity):
cubicCurve1 = new CubicCurve2D.Double(
p1.x, p1.y,
p1Control1.x, p1Control1.y,
p2Control1.x, p2Control1.y,
p2.x, p2.y);
cubicCurve2 = new CubicCurve2D.Double(
p2.x, p2.y,
p2Control2.x, p2Control2.y,
p3Control1.x, p3Control1.y,
p3.x, p3.y);
cubicCurve3 = new CubicCurve2D.Double(
p3.x, p3.y,
p3Control2.x, p3Control2.y,
p1Control1.x, p1Control1.y,
p1.x, p1.y);
g2D.setPaint(Color.BLUE);
g2D.draw(cubicCurve1);
g2D.draw(cubicCurve2);
g2D.draw(cubicCurve3);
Here's how I solved my problem:
GeneralPath shape = new GeneralPath();
shape.moveTo(cubicCurve1.x1, cubicCurve1.y1);
shape.curveTo(cubicCurve1.ctrlx1, cubicCurve1.ctrly1, cubicCurve1.ctrlx2, cubicCurve1.ctrly2, cubicCurve1.x2, cubicCurve1.y2);
shape.curveTo(cubicCurve2.ctrlx1, cubicCurve2.ctrly1, cubicCurve2.ctrlx2, cubicCurve2.ctrly2, cubicCurve2.x2, cubicCurve2.y2);
shape.curveTo(cubicCurve3.ctrlx1, cubicCurve3.ctrly1, cubicCurve3.ctrlx2, cubicCurve3.ctrly2, cubicCurve1.x1, cubicCurve1.y1);
g2D.draw(shape);
g2D.setClip(shape);
// Draw an image
g2D.drawImage(image, 0, 0, this);
Related
Here is the picture I take with my USB camera. My camera has an angle with horizontal line, the target is on the bottom, with parallel and orthogonal lines delimiting rectangles. Post-it is a control marker of the center-rectangle.
Then I process several step-by-step processing in order to adjust the 'tilt' of the view and to extract lines.
Here is the line extraction without transform :
{"type":"toGray"} => mat.cvtColor( cv4.COLOR_BGR2GRAY);
{"type":"toBlur","size":10} => mat.gaussianBlur( new cv4.Size( size, size),0);
{"type":"toCanny","low":50,"high":150} => mat.canny( low_threshold, high_threshold);
{"type":"getLines","rho":1,"theta":0.017453292222222222,"threshold":15,"min_line_length":50,"max_line_gap":20 }] => let lines = mat.houghLinesP( rho, theta, threshold, min_line_length, max_line_gap);
Result is :
Now, I want to correct the tilt of view, using 'warpAffine' function, before extracting lines.
I select four points of the centered rectangle, in order to build two "three points array" (src, dst):
matTransf = cv4.getAffineTransform( srcPoints, dstPoints);
resultMat = mat.warpAffine( matTransf, new cv4.Size( mat.cols, mat.rows));
The result is the following:
Where is the mistake ?
I have tried too :
// four points at each corner of the rectangle, srcPoints for the picture, and dstPoints for the theoric shape
// With getPerspectiveTransform
matTransf = cv4.getPerspectiveTransform( srcPoints, dstPoints);
resultMat = mat.warpPerspective( matTransf, new cv4.Size( mat.cols, mat.rows));
// With findHomography
let result = cv4.findHomography( srcPoints, dstPoints);
matTransf = result.homography;
resultMat = mat.warpPerspective( matTransf, new cv4.Size( mat.cols, mat.rows));
Result is :
Best regards.
The transformation is not an affinity, it is a perspective described by a homography. Select in the image four corners of a physical rectangle, map them to points in a rectangle with the same aspect ratio as the physical one, estimate the homography from them (findHomography), finally warp (warpPerspective).
In reference to this question
Drawing a line between two points using SceneKit
I'm drawing a line in 3D and want to make it thicker by using this code
func renderer(aRenderer: SCNSceneRenderer, willRenderScene scene: SCNScene, atTime time: NSTimeInterval) {
//Makes the lines thicker
glLineWidth(20)
}
but it doesn't work, iOS 8.2.
Is there another way?
Update
From the docs
https://developer.apple.com/library/prerelease/ios/documentation/SceneKit/Reference/SCNSceneRendererDelegate_Protocol/index.html#//apple_ref/occ/intfm/SCNSceneRendererDelegate/renderer:updateAtTime:
I did add SCNSceneRendererDelegate and a valid line width but still could not get the line width to increase.
You cannot assign any number to glLineWidth().
You can check the range of possible values of glLineWidth()by:
glGetFloatv(GL_LINE_WIDTH_RANGE,sizes);
One crazy idea is to use a cylinder for drawing lines ;). I use it when I want to have nice and controllable lines but I am not aware of a handy OpenGl function to do so.
#G Alexander: here you go my implementation of cylinder. It is a bit tedious but it is what I have at the moment.
If you give me points p0 and p1, Vector normal=(p1-p0).normalize() would be the axis of the cylinder.
pick point p2 that is not on the vector Normal.
q=(p2-p0).normalize();
normal.crossproduct(q)=v0;
normal.crossproduct(v0)=v1;
Having these two vectors you can have circles with any radius that are stacked along the axis of the cylinder using the following function (A cylinder is a stack of circles):
public Circle make_circle(Point center, Vector v0, Vector v1, double radius)
{
Circle c;
for (double i = 0; i < 2 * Math.PI; i += 0.05)
{
Point p = new Point(center + radius * Math.Cos(i) * v0 + radius * Math.Sin(i) * v1);
c.Add(p);
}
return c;
}
You only need to make circles using this function along the axis of the cylinder:
List<Circle> Cylinder = new List<Circle>();
for(double i=0;i<1;i+=0.1)
{
Cylinder.add( make_circle(P0+i*normal, v0, v1,radius);
}
Now you should take two consecutive circles and connect them with quads by sampling uniformly.
I have implemented it this way since I had circles implemented already.
A simpler way to implement is make the circle along the x axis and then rotate and translate it to p0 and make it align with normal or to use gluCylinder if you are the fan of Glu....
Hopefully it works for you.
I am trying to calculate the coordinates along a circle corresponding to the tap location. The coordinates should be on the border of the circle nearest to the tap location (e.g. the border that is less distant from the radius). To facilitate this I am detecting only taps that are distant by 80% of the radius from the circle center.
Input:
P (GPPoint) - center of the circle
P1 (GPPoint) current position of an image displayed
r (float) radius of circle
P3 (CGPoint) user tap coordinate
Desired output:
P2 (CGPoint) - new coordinates for the image corresponding to P3 but along the circle. Sorry for the bad explanation, I try to explain it in other words: once the user taps on the screen I would like to move the image in P2. P2 should be derived by moving P2 to the border of the circle. It should be possible to do so by using the radius information.
The idea is to create from P3 coordinates a new coordinate called P2 as described above - the key is that P2 distance from the centre should correspond exactly to the radius and the ANGLE should be the same as tapPoint.
Would anyome be able to suggest a formula to calculate the corresponding coordinate given a tap? I simply need to calculate P3 using the input I have.
Code so far:
-(void)tapInImageView:(UITapGestureRecognizer *)tap
{
CGPoint tapPoint = [tap locationInView:tap.view];
if ([self isInOuternCircle:tapPoint]) {
// then create from tapPoint coordinates a new coordinate P2 as described above - but have no idea how.. the key is that P2 distance from the centre should correspond exactly to the radius and the ANGLE should be the same as tapPoint.
}
}
-(BOOL)isInOuternCircle:(CGPoint)point
{
double distanceToCenter = sqrt((point.x - _timerView.center.x)*(point.x - _timerView.center.x) + (point.y - _timerView.center.y)*(point.y - _timerView.center.y));
if (distanceToCenter < _innerCircleRadius) {
return false;
}
return true;
}
I've done this once before, but the math usually depends on how you've set up your coordinate system, so I'll just outline what I did. You'll need a bit of geometry, and a few formulae to determine the new coordinate along the circle.
Calculate the formula of a line passing through the center (P) and your tap point (P3) using this: http://en.wikipedia.org/wiki/Linear_equation#Two-point_form
Determine the equation for your circle: http://en.wikipedia.org/wiki/Circle#Equations
Using the above two equations, you'll have a system of a linear and a quadratic equation: http://www.mathsisfun.com/algebra/systems-linear-quadratic-equations.html
Once you have the equation above, you need to solve it. The result will yield two possible points (the line will intersect the circle in two places), and the point you are looking for is the point closer the tap point. In this case, just compare the distances to P3 between the two solutions, and the shorter distance will show your required solution - P2.
I am trying to create an ellipses. I used bodyWithEdgeLoopFromPath and it worked but there seems to be something wrong with it because sometimes other objects get caught in the middle of it.
But I want the ellipses to be solid, So I tried bodyWithPolygonFromPath (I want it static)
horizontalOval = [[SKShapeNode alloc] init];
theRect = CGRectMake(0, 0, self.frame.size.width/6 , 15);
CGMutablePathRef ovalPath = CGPathCreateMutable();
CGPathAddEllipseInRect(ovalPath, NULL, theRect);
horizontalOval.path = ovalPath;
horizontalOval.fillColor = [UIColor blueColor];
horizontalOval.physicsBody.dynamic = NO;
horizontalOval.physicsBody = [SKPhysicsBody bodyWithPolygonFromPath:ovalPath];
But got the error
SKPhysicsBody: Error attempting to create polygon with 17 vertices, maximum is 12
How do I create complex paths and make them solid?
Also when I pud it in position self.frame.size.width/2 and self.frame.size.height/2 It doesn't stay center, it goes a little to the right.
I had to theRect = CGRectMake(-40, 0........) to make it center but why is that?
UIBezierPath* ovalPath = [UIBezierPath bezierPathWithOvalInRect: _paddleRect];
But has 13 vertices. Trying to use PaintCode.
You can think of an edge body as one that has no volume, just the edges, a body with 'negative space' - that's why your objects got caught in the middle of it. As the Sprite Kit Programming Guide says:
The main difference between a edge and a volume is that an edge permits movement inside its own boundaries, while a volume is considered a solid object.
Since you want your oval to be a solid object, you do need a volume-based body. For these bodies, you have three options to create their shape: a circle (bodyWithCircleOfRadius:), a rectangle (bodyWithRectangleOfSize:), or a polygon (bodyWithPolygonFromPath:).
For an oval shape, you probably have to draw a polygon - however, the Sprite Kit physics engine will only accept those with a maximum of 12 vertices (that's why you were getting an error when drawing an actual ellipse). Your best bet is drawing a polygon using a helper tool, such as this one: http://dazchong.com/spritekit/ - just drag and drop your sprite and draw the path. Remember that the polygon must be convex (no angles over 180 degrees inside it) and that it can have a maximum of 12 vertices.
Also check out this answer for a similar issue: Ellipse SKPhysicsBody
I'm writing an application that will calculate a CGPoint and show a mark in an envelope (a diagram if you like). My envelope is just part of the background image in an UIImageView. What I want to do is to construct a sort of "line", corresponding to the envelopes limits (they're not straight lines, but curves) so that if the calculated CGPoint is to the left of this line, or to the right of another line, then the calculated point is not approved. Where it to be in the middle of these two, it's approved.
I was first thinking of drawing lines using CoreGraphics, but I'm not sure if one could check whether the calculated CGPoint is to the right or left of those lines.
The envelope is only 149px high, so I was also thinking of putting together a dictionary, where the keys where the y position and the values where the x position of the pixels that represented that defining boundary line.
The application is rather simple and is not animating anything. Does anybody have an idea of how to best come up with a solution for this sort of behavior?
You can do this by creating a CGPath that represents your boundary lines (the outline of your envelope) and testing that a point is contained in it with CGPathContainsPoint.
You'll have to do some trial and error to construct a CGPath that matches your envelope shape, try filling it in the drawRect method to see what your path actually is.
Here's an example with a circle path:
CGPoint viewCenter = CGPointMake(100,100);
CGPoint checkPoint = CGPointMake(110,110);
UIBezierPath *bpath = [UIBezierPath bezierPathWithArcCenter:viewCenter radius:50 startAngle:0 endAngle:DEGREES_TO_RADIANS(360) clockwise:YES];
CGPathRef path = [bpath CGPath];
BOOL inPath = CGPathContainsPoint(path, NULL, checkPoint, NO);
Here I have DEGREES_TO_RADIANS defined like this:
#define DEGREES_TO_RADIANS(angle) ((angle) / 180.0 * M_PI)