Find area inside closed object in ios - ios

I want to calculate the area inside an object which is any closed object like rectangle ,square ,polygon etc.
I can not get exact solution to do this.Please help to find it.
Thanks.

For arbitrary polygons with known vertice coordinates you can use Shoelace formula
A = 1/2 * Abs(Sum{i=0..n-1} (X[i] * Y[i+1] - X[i+1] * Y[i]) )
where for i=n-1 take i+1=0

I am using this method which will give me closed object's area.It may be helpful for you.
-(double)areaWithXpts :(NSArray *)xpts withYpts :(NSArray *)ypts totalPoints :(int)numPoints
{
double area=0;
int j=numPoints-1;
for(int i=0 ; i < numPoints;i++)
{
area=area+([[xpts objectAtIndex:j] floatValue]+[[xpts objectAtIndex:i] floatValue])*([[ypts objectAtIndex:j] floatValue]-[[ypts objectAtIndex:i] floatValue]);
j=i;
}
double areaVal=area/2;
NSLog(#"Area is :%f",areaVal);
return areaVal;
}
Usage :
Array of X points
NSArray *xArray =[NSArray arrayWithObjects:#"0", #"10", #"10", #"29",nil];
Array of Y points
NSArray *yArray =[NSArray arrayWithObjects:#"4", #"26", #"26", #"4",nil];
Total points = Array count.
Note: x array and y array both have same count.
double objectArea = [self areaWithXpts:xArray withYpts:yArray totalPoints:4];
Or you can check this answer also - Area calculation in objective c
And about area with curve shape object : you can find reference from this link - Curve shape object area reference

Related

iOS-Charts how to allow clicks only on plotted points?

I'm using iOS charts framework to plot this chart, I want to detect tap or touch only on the line's path or on the small circle's on the lines.
My question is,
Is there any default code block to do this?
I tried comparing the entry.value with the array plotted(as in the following code), but it doesn't workout.
-(void)chartValueSelected:(ChartViewBase *)chartView entry:(ChartDataEntry *)entry dataSetIndex:(NSInteger)dataSetIndex highlight:(ChartHighlight *)highlight{
if ([arrayOfPlottedValues containsObject:[NSNumber numberWithInt:(int)entry.value]]) {
//Tapped on line path
}
else{
//Tapped on empty area
}
}
Any insights will be appreciated.
eg : Line chart
I found a way by considering #Wingzero's suggestion, but the major difference was that, I just used the touch point to find out if its on the "marker" or if its outside it. I'm not sure if its the right way, but the solution is,
-(void)chartValueSelected:(ChartViewBase *)chartView entry:(ChartDataEntry *)entry dataSetIndex:(NSInteger)dataSetIndex highlight:(ChartHighlight *)highlight{
//-----------------------------------------------------getting recognizer value
UIGestureRecognizer *recognisedGesture = [chartView.gestureRecognizers objectAtIndex:0];
CGPoint poinOfTouch =[recognisedGesture locationInView:chartView];
CGPoint poinOfMarker =[chartView getMarkerPositionWithEntry:entry highlight:highlight];
if (check if the chartview is BarChartView and if true) {
//-----------------------------------------------------If you want to detect touch/tap only on barchartview's bars
if (poinOfTouch.y > poinOfMarker.y) {
NSLog(#"within the bar area!");
}
else{
NSLog(#"Outside the bar area!");
}
}
else
{
//-----------------------------------------------------If you want to detect touch/tap only on linechartView's markers
//-----------------------------------------------------creating two arrays of x and y points(possible nearby points of touch location)
NSMutableArray *containingXValue = [[NSMutableArray alloc]init];
NSMutableArray *containingYValue = [[NSMutableArray alloc]init];
for (int i =0 ; i<5; i++) {
int roundedX = (poinOfMarker.x + 0.5);
int sumXValuesPositive = roundedX+i;
[containingXValue addObject:[NSNumber numberWithInt:sumXValuesPositive]];
int sumXValuesNegative = roundedX-i;
[containingXValue addObject:[NSNumber numberWithInt:sumXValuesNegative]];
int roundedY = (poinOfMarker.y + 0.5);
int sumYValuesPositive = roundedY+i;
[containingYValue addObject:[NSNumber numberWithInt:sumYValuesPositive]];
int sumYValuesNegative = roundedY-i;
[containingYValue addObject:[NSNumber numberWithInt:sumYValuesNegative]];
}
//-----------------------------------------------------------------------------------------------------------------------------------------
int roundXPointTOuched = (poinOf.x + 0.5);
int roundYPointTOuched = (poinOf.y + 0.5);
//-----------------------------------------------------check if touchpoint exists in the arrays of possible points
if ([containingXValue containsObject:[NSNumber numberWithInt:roundXPointTOuched]] && [containingYValue containsObject:[NSNumber numberWithInt:roundYPointTOuched]])
{
// continue, the click is on marker!!!!
}
else
{
// stop, the click is not on marker!!!!
}
//-----------------------------------------------------------------------------------------------------------------------------------------
}
}
}
Edit : The initial solution was applicable only for the line chart, Now if this same situation arises for bar chart, you could handle it with the above code itself.
Man, I'd been running around it for a while now, feeling really great for getting a positive lead. There is no direction for this issue yet, hope this will be useful for someone like me cheers!
P.S. I'm marking this as answer just to make sure, it reaches the needful :). Thanks
It has a default highlight logic, that is, calculate the closest dataSet and xIndex, so we know which data to highlight.
You can customize this logic to restrain the allowed smallest distance. e.g. define the max allowed distance is 10, if the touch point is away from the closest dot > 10, you return false and not highlgiht.
Highlighter is a class, like BarChartHighlighter, ChartHighlighter, etc.
Update towards your comment:
when you tapped, the delegate method get called, so you know which data is highlighted. Your codes seems fine, however the condition code is blackbox to me. But the delegate will be called for sure, so you only have to worry about your logic.

(iOS) Accelerometer Graph (convert g-force to +/- 128) granularity

I am using this Accelerometer graph from Apple and trying to convert their G-force code to calculate +/- 128.
The following image shows that the x, y, z values in the labels do not match the output on the graph: (Note that addX:y:z values are what is shown in the labels above the graph)
ViewController
The x, y, z values are received from a bluetooth peripheral, then converted using:
// Updates LABELS
- (void)didReceiveRawAcceleromaterDataWithX:(NSInteger)x Y:(NSInteger)y Z:(NSInteger)z
{
dispatch_async(dispatch_get_main_queue(), ^{
_labelAccel.text = [NSString stringWithFormat:#"x:%li y:%li z:%li", (long)x, (long)y, (long)z];
});
}
// Updates GRAPHS
- (void)didReceiveAcceleromaterDataWithX:(NSInteger)x Y:(NSInteger)y Z:(NSInteger)z
{
dispatch_async(dispatch_get_main_queue(), ^{
float xx = ((float)x) / 8192;
float yy = ((float)y) / 8192;
float zz = ((float)z) / 8192;
[_xGraph addX:xx y:0 z:0];
[_yGraph addX:0 y:yy z:0];
[_zGraph addX:0 y:0 z:zz];
});
}
GraphView
- (BOOL)addX:(UIAccelerationValue)x y:(UIAccelerationValue)y z:(UIAccelerationValue)z
{
// If this segment is not full, then we add a new acceleration value to the history.
if (index > 0)
{
// First decrement, both to get to a zero-based index and to flag one fewer position left
--index;
xhistory[index] = x;
yhistory[index] = y;
zhistory[index] = z;
// And inform Core Animation to redraw the layer.
[layer setNeedsDisplay];
}
// And return if we are now full or not (really just avoids needing to call isFull after adding a value).
return index == 0;
}
- (void)drawLayer:(CALayer*)l inContext:(CGContextRef)context
{
// Fill in the background
CGContextSetFillColorWithColor(context, kUIColorLightGray(1.f).CGColor);
CGContextFillRect(context, layer.bounds);
// Draw the grid lines
DrawGridlines(context, 0.0, 32.0);
// Draw the graph
CGPoint lines[64];
int i;
float _granularity = 16.f; // 16
NSInteger _granualCount = 32; // 32
// X
for (i = 0; i < _granualCount; ++i)
{
lines[i*2].x = i;
lines[i*2+1].x = i + 1;
lines[i*2].y = xhistory[i] * _granularity;
lines[i*2+1].y = xhistory[i+1] * _granularity;
}
CGContextSetStrokeColorWithColor(context, _xColor.CGColor);
CGContextStrokeLineSegments(context, lines, 64);
// Y
for (i = 0; i < _granualCount; ++i)
{
lines[i*2].y = yhistory[i] * _granularity;
lines[i*2+1].y = yhistory[i+1] * _granularity;
}
CGContextSetStrokeColorWithColor(context, _yColor.CGColor);
CGContextStrokeLineSegments(context, lines, 64);
// Z
for (i = 0; i < _granualCount; ++i)
{
lines[i*2].y = zhistory[i] * _granularity;
lines[i*2+1].y = zhistory[i+1] * _granularity;
}
CGContextSetStrokeColorWithColor(context, _zColor.CGColor);
CGContextStrokeLineSegments(context, lines, 64);
}
How can I calculate the above code to show the correct accelerometer values on the graph with precision?
I post this as an aswer not a comment, because I have not enough reputation, but what I'll write might be enough to send you in the right direction, that it even may count as an answer...
Your question still doesn't include what is really important. I assume the calculation of the xx/yy/zz is no problem. Although I have no idea what the 8192 is supposed to mean.
I guess the preblem is in the part where you map your values to pixel coordinates...
the lines[] contains your values in a range of 1/8192th of the values in the label. so your x value of -2 should be at a pixel position of -0.0000something, so slightly(far less than 1 Pixel) above the view... Because you see the line a lot further down there must be some translation in place (not shown in your code)
The second part that is important but not shown is DrawGridlines. Probably in there is a different approach to map the values to pixel-coordinates...
Use the debugger to check what pixel-coordinates you get when draw your +127-line and what you get if you insert the value of +127 in your history-array
And some Ideas for improvements when reading your code:
1.)Put the graph in it's own class that draws one graph(and has only one history. Somehow you seem to have that partially already (otherwise I cannot figure out your _xGraph/_yGraph/_zGraph) But on the other hand you draw all 3 values in one drawLayer??? Currently you seem to have 3*3 history buffers of which 3*2 are filled with zeros...
2.) use one place where you do the calculation of Y that you use both for drawing the grid and drawing the lines...
3.) use CGContextMoveToPoint(); + CGContextAddLineToPoint(); instead of copying into lines[] with these ugly 2*i+1 indecies...

Add a sprite node into a mutable array

This is making me feel like a bumbling idiot, and I seem like one by asking this.
I have a board game-like-game where I'm adding spaces (type DDSpace's for each space, a subclass of NSObject) to a mutable array (NSMutableArray).
Here's the function to load the spaces into the view (loadSpaces) so far:
NSLog(#"amount of spaces: %i", amountOfSpaces);
for (int i = 0; i < amountOfSpaces; i++) {
DDSpace *space = [DDSpace new];
[space setupSpriteWithTheme:gamePlace];
[spacesArray addObject:space];
}
int num = 0;
// INITIAL SPACE IS SPACE 0.
NSLog(#"adding spaces to scene... self.width = %f, count of space array = %i", self.size.width, spacesArray.count);
for (DDSpace* space in spacesArray) {
CGFloat x = 100.0 + (num * 225.0);
NSLog(#"x at num%i = %f.", num, x);
space.sprite.position = CGPointMake(x, (self.size.width / 3.0));
space.sprite.name = [NSString stringWithFormat:#"space%ld",(long)num];
if (space.sprite.position.x < self.size.width) {
NSLog(#"adding space.");
[self addChild:space.sprite];
}
}
NSLog(#"loadSpaces function finished.");
The first game loads 1,000 spaces. The function first logs the amount of spaces to make sure that's set properly (and it is), then it logs the width of the screen and the count of spaces in the array (the array's count is 0), and then everything below that simply adds the ones that fit onto the screen onto the view.
My goal is to add the spaces to the spacesArray array (an NSMutableArray) so I can access the other spaces later on, in case a character "takes their turn" (I'll have logic in there to move the others backwards, but to do this, I need an array of spaces).
My question is, how do I go about adding the DDSpaces into the spacesArray array? Is the addObject: method correct? Am I simply doing something dumb with it?
None of the spaces appear on the scene, either.
I think you need this before adding objects to it.
spaceArray = [NSMutableArray Array];
And add objects like this ( like you did )
[spacesArray addObject:space];

Remove last digit when it's a 0 in double (or any other option) when comparing

I'm adding a bunch of coordinates into quad tree and when I'm asking for the closest coordinate near my location, sometimes I've coordinate with 0 at the end, added automatically perhaps by the quad tree or I don't know how.
The problem is when I'm asking the double value in my core data using predicate it won't match because of the 0 digit addition to the number.
I thought about removing it when I've 0 but I'm sure there is a better way doing it.
For example:
Near location 31.123456, 34.123456, the nearest is 31.123444, 34.123450
when '34.123450' is actually 34.12345 in the database.
//Convert float to String
NSString *str_lat = #"34.123450";
NSString *trimmedString=[str_lat substringFromIndex:MAX((int)[str_lat length]-1, 0)];
if([trimmedString isEqualToString:#"0"])
{
str_lat = [str_lat substringToIndex:[str_lat length] - 1];
}
else
{
}
NSLog(#"%#",str_lat);
First: You should not store numbers as strings. 7.3 and 7.30 are the same values with simply different representations. You should not compare the representations, but the value.
Second: You should not compare floating-point numbers with == but their difference to a delta. In a calculation precision might get lost, rounding is applied and so on. The "mathematical" equal values might be physical different by a more or less small amount.
// remove the zeros from values (if you have them as floats)
NSString *valueFromTheDataBase = [NSString stringWithFormat:#"%g", 34.123450];
NSString *yourValue = [NSString stringWithFormat:#"%g", 34.12345];
if([yourValue isEqualToString:valueFromDataBase]) {
// they are equal
}
OR Make Them floats and compare them
// make them floats and compare them
CGFloat floatFromDB = [valueFromDB floatValue];
CGFloat yourFloat = [yourString floatValue];
if((floatFromDB - yourFloat) == 0) {
// they are equal
}
UPDATED as #Amin Negm says

Problem assigning values to Mat array in OpenCV 2.3 - seems simple

Using the new API for OpenCV 2.3, I am having trouble assigning values to a Mat array (or say image) inside a loop. Here is the code snippet which I am using;
int paddedHeight = 256 + 2*padSize;
int paddedWidth = 256 + 2*padSize;
int n = 266; // padded height or width
cv::Mat fx = cv::Mat(paddedHeight,paddedWidth,CV_64FC1);
cv::Mat fy = cv::Mat(paddedHeight,paddedWidth,CV_64FC1);
float value = -n/2.0f;
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
fx.at<cv::Vec2d>(i,j) = value++;
value = -n/2.0f;
}
meshElement = -n/2.0f;
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
fy.at<cv::Vec2d>(i,j) = value;
value++;
}
Now in the first loop as soon as j = 133, I get an exception which seems to be related to depth of the image, I cant figure out what I am doing wrong here.
Please Advise! Thanks!
You are accessing the data as 2-component double vector (using .at<cv::Vec2d>()), but you created the matrices to contain only 1 component doubles (using CV_64FC1). Either create the matrices to contain two components per element (with CV_64FC2) or, what seems more appropriate to your code, access the values as simple doubles, using .at<double>(). This explodes exactly at j=133 because that is half the size of your image and when treated as containing 2-component vectors when it only contains 1, it is only half as wide.
Or maybe you can merge these two matrices into one, containing two components per element, but this depends on the way you are going to use these matrices in the future. In this case you can also merge the two loops together and really set a 2-component vector:
cv::Mat f = cv::Mat(paddedHeight,paddedWidth,CV_64FC2);
float yValue = -n/2.0f;
for(int i=0;i<n;i++)
{
float xValue = -n/2.0f;
for(int j=0;j<n;j++)
{
f.at<cv::Vec2d>(i,j)[0] = xValue++;
f.at<cv::Vec2d>(i,j)[1] = yValue;
}
++yValue;
}
This might produce a better memory accessing scheme if you always need both values, the one from fx and the one from fy, for the same element.

Resources