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• CIE XYZ colorspace: is it RGBA or XYZA?

  - by Tronic

  I plan to write a painting program based on linear combinations of xy plane points (0,1), (1,0 ) and (0,0). Such system works identically to RGB, except that the primaries are not within the gamut but at the corners of a triangle that encloses the entire gamut, therefore allowing for all colors to be reproduced. I have seen the three points being referred to as X, Y and Z (upper case) somewhere, but I cannot find the page anymore. My pixel format stores the intensity of each of those three components the same way as RGB does, together with alpha value. This allows using pretty much any image manipulation operation designed for RGBA without modifying the code. What is my format called? Is it XYZA, RGBA or something else? Google doesn't seem to know of XYZA and RGBA will get confused with sRGB + alpha (which I also need to use in the same program). Notice that the primaries X, Y and Z and their intensities have little to do with the x, y and z coordinates (lower case) that are more commonly used.

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• OpenGL - drawing 2D polygons shapes with texture

  - by plonkplonk

  I am trying to make a few effects in a C+GL game. So far I draw all my sprites as a quad, and it works. However, I am trying to make a large ring appear at times, with a texture following that ring, as it takes less memory than a quad with the ring texture inside. The type of ring I want to make is not a round-shaped GL mesh ring (the "tube" type) but a "paper" 2D ring. That way I can modify the "width" of the ring, getting more of the effect than a simple quad+ring texture. So far all my attempts have been...kind of ridiculous, as I don't understand GL's coordinates too well (and I can't really understand the available documentation...I am just a designer with no coder help or background. A n00b, basically). glBegin(GL_POLYGON); for(i = 0;i < 360; i += 10){ glTexCoord2f(0, 0); glVertex2f(Cos(i)*(H-10),Sin(i)H); glTexCoord2f(0, HP); glVertex2f(Sin(i)(H-10),Cos(i)*(H-10)); glTexCoord2f(WP, HP); glVertex2f(Cos(i)H,Sin(i)(H-10)); glTexCoord2f(WP, 0); glVertex2f(Sin(i)*H,Cos(i)*H); } glEnd(); This is my last attempt, and it seems to generate a "sunburst" from the right edge of the circle instead of a ring. It's an amusing effect but definitely not what I want. Other results included the circle looking exactly the same as the quad textured (aka drawing a sprite literally) or something that looked like a pop-art filter, by working on this train of thought. Seems like my logic here is entirely flawed, so, what would be the easiest way to obtain such a ring? No need to reply in code, just some guidance for a non-math-skilled user...

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• Android beginner: understanding MotionEvent actions

  - by Dave

  I am having trouble getting my activity to return a MotionEvent.ACTION_UP. Probably a beginner's error. In LogCat, I'm only seeing the ACTION_MOVE event (which is an int value of 3). I also see the X/Y coordinates. No ACTION_DOWN and no ACTION_UP. I looked everywhere for a solution. I found one question on a forum that seems to be the same as my issue, but no solution is proposed: http://groups.google.com/group/android-developers/browse_thread/thread/9a9c23e40f02c134/bf12b89561f204ad?lnk=gst&q=ACTION_UP#bf12b89561f204ad Here's my code: import android.app.Activity; import android.os.Bundle; import android.util.Log; import android.view.MotionEvent; import android.webkit.WebView; public class Brand extends Activity { public WebView webview; public float currentXPosition; public float currentYPosition; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); webview = new WebView(this); setContentView(webview); webview.loadUrl("file:///android_asset/Brand.html"); } @Override public boolean onTouchEvent(MotionEvent me) { int action = me.getAction(); currentXPosition = me.getX(); currentYPosition = me.getY(); Log.v("MotionEvent", "Action = " + action); Log.v("MotionEvent", "X = " + currentXPosition + "Y = " + currentYPosition); if (action == MotionEvent.ACTION_MOVE) { // do something } if (action == MotionEvent.ACTION_UP) { // do something } return true; } }

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• Python fit polynomial, power law and exponential from data

  - by Nadir

  I have some data (x and y coordinates) coming from a study and I have to plot them and to find the best curve that fits data. My curves are: polynomial up to 6th degree; power law; and exponential. I am able to find the best fit for polynomial with while(i < 6): coefs, val = poly.polyfit(x, y, i, full=True) and I take the degree that minimizes val. When I have to fit a power law (the most probable in my study), I do not know how to do it correctly. This is what I have done. I have applied the log function to all x and y and I have tried to fit it with a linear polynomial. If the error (val) is lower than the others polynomial tried before, I have chosen the power law function. Am I correct? Now how can I reconstruct my power law starting from the line y = mx + q in order to draw it with the original points? I need also to display the function found. I have tried with: def power_law(x, m, q): return q * (x**m) using x_new = np.linspace(x[0], x[-1], num=len(x)*10) y1 = power_law(x_new, coefs[0], coefs[1]) popt, pcov = curve_fit(power_law, x_new, y1) but it seems not to work well.

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• Overlaying 2D paths on UIImage without scaling artifacts

  - by tat0

  I need to draw a path along the shape of an image in a way that it is always matching its position on the image independent of the image scale. Think of this like the hybrid view of Google Maps where streets names and roads are superimposed on top of the aerial pictures. Furthermore, this path will be drawn by the user's finger movements and I need to be able to retrieve the path keypoints on the image pixel coordinates. The user zooms-in in order to more precisely set the paths location. I manage to somehow make it work using this approach: -Create a custom UIView called CanvasView that handles touches interaction and delivers scaling, rotation, translation values to either the UIImageView or PathsView (see bellow) depending on a flag: deliverToImageOrPaths. -Create a UIImageView holding the base image. This is set as a children of CanvasView -Create a custom UIView called PathsView that keeps track of the 2D paths geometry and draws itself with a custom drawRect. This is set as children of the UIImageView. So hierarchy: CanvasView - UIImageView -PathsView In this way when deliverToImageOrPaths is YES, finger gestures transforms both the UIImageView and its child PathsView. When deliverToImageOrPaths is NO the gestures affect only the PathsView altering its geometry. So far so good. QUESTION: The problem I have is that when scaling the base UIImageView (via its .transform property) the PathsView is scaled with aliasing artifacts. drawRect is still being called on the PathsView but I guess it's performing the drawing using the original buffer size and then interpolating. How can I solve this issue? Are there better ways to implement these features? PS: I tried changing the PathsView layer class to CATiledLayer with levelsOfDetailBias 4 and levelsOfDetail 4. It solves the aliasing problem to some extent but it's unacceptable slow to render.

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• How to get top and left style property values in Javascript

  - by Dude-Dastic

  Hi all, I have a little bit of Javascript that almost works correctly. Here's the code: function toggle(curlink) { curlink.style.backgroundColor = curlink.style.backgroundColor == "yellow" ? "transparent" : "yellow"; var maindiv = document.getElementById("grid"); var links = maindiv.getElementsByTagName("a"); var list = ""; for (var i = 0; i < links.length; ++i) { var link = links[i]; if (link.style.backgroundColor == "yellow") { list += ("," + parseInt(link.style.left, 10) + "-" + parseInt(link.style.top, 10)); } } document.theForm.theList.value = list.substring(1); return false; }; window.onload = function() { var links = document.getElementById("grid").getElementsByTagName("a"); for (var i = 0; i < links.length; ++i) { links[i].onclick = function() { return toggle(this); } } }; The issue is with line #9; it only works when I specify values for the top and left style property of every link in the array. How do I get the top and left style property values (or X and Y coordinates) of each link in the array with Javascript when those values aren't given? Also, what would the code above look like in jquery? Not that it's needed - I just want to reduce the code a little and dabble in the jquery framework (I'm a Javascript newbie). Thanks in advance, Dude-Dastic

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• List of objects or parallel arrays of properties?

  - by Headcrab

  The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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• Forwarding first responder to UIScrollView unsuccessful

  - by Winston

  Hello, I am trying to create an image cropping bpx whereby the underlying image can be zoomed an scrolled while the cropping "maskview" layer stays the same and the corners can be dragged in any direction. To achieve this, the ImageView is added to a UIScrollView, and this is added to the SelectionViewController.view . I then add the cropping "maskview" layer to the SelectionViewController.view. I did this instead of adding to the scrollview so that the cropping maskview won't be expanded when the underlying image expands. @interface SelectionViewController : UIViewController <UIScrollViewDelegate> { UIImageView *photoview; // Added to self.scrollview MaskedView *maskedview; // Added to self.view UIScrollView *scrollview; // Added to self.view } The maskview has first responder status and responds accordingly. However, the only event I am interested in the maskview is if any of the corners are dragged (this works fine). The problem I want to try to solve is two-fold: If it is a pinch or zoom gesture, I am trying to forward the responder to the UIScrollview using: [self.nextResponder touchesMoved:touches withEvent:event]; The scrollview does not seem to respond. I have confirmed that the self.nextResponder after the maskedview is the SelectionViewController's view itself. From there, it doesn't seem like the UIScrollview responds. It does respond fine if I remove the cropping maskedview. If I zoom in on the underlying image and the cropping maskview rectangle is still the same, I want to now crop the actual zoomed image. Let's say for the upper left hand corner of the crop box, how can I find what the coordinates translates to in the underlying UIImageView now that the image has been zoomed? Any insight into either of these questions would be appreciated. Thank you, Winston

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• Best approach for a multi-tab ASP.NET AJAX control?

  - by NovaJoe

  Looking for some implementation advice: I have a page that has a 3-tab ajaxToolkit:TabContainer. The purpose of the page is to expose a calculator that has two basic inputs: geo-location and date. The three tabs are labeled "City and State", "Postal Code", and "GPS Coordinates". The layout of each tab container is the same for each tab, with the exception of the location section; the location section changes because each type of location has different inputs. For example, to specify city/state, there will be three fields: city, country, and state (country and state will use cascading drop-down lists). But Postal code requires only one field (which will validate via regular expression for allowed countries). See the example design mockup: So, what I WOULD LIKE to do (in order to minimize duplicate code), is to have a common control that contains the layout and structure of the calculator without specifying anything about the location section. Then, I'd like to be able to pull in each of the unique location controls based on what tab is selected. The tab structure exists at the page level, not in a control. Any advice? I was looking at templated controls (see MSDN article here), but I'm not convinced that it's the right solution. If I HAVE to create three separate controls with similar layouts and common elements, then that's what I have to do. But REALLY, I'd prefer a more elegant, inheritance-based solution. Any advice would be greatly appreciated. Thanks.

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• Positioning problem in VIsta when Aero Theme is enabled

  - by Adeel Rehman

  Hi, I have a Windows form which has tab pages. On a Tab Page, I have a Combo Box. When I click the combobox a drop down opens up just below the combo box to give the impression of a drop down. The drop down is a windows form and this is how I set its position Popup.Location = control.PointToScreen(parentcontrol.PointToClient(new System.Drawing.Point(0, control.Height))); Popup = drop down that opens below the combo box (Windows Form) control = my combo box (Combo Box) parentcontrol = the windows form on which the control is present (Parent Form) Problem:- The X coordinate is not plotted correctly on the screen with Aero theme enabled. This works perfectly fine on XP (with some variance in y due to tablelayout panel i assume). But when i use the same code on Vista with Aero theme enabled the x-cordinate wanders away about 20-30 pixels. If I Turn Aero theme off on Vista, it works fine. I have found the X and Y coordiantes calculated in both cases are the same. But the way Vista draws these coordinates on the screen (when aero theme is enabled) is different. Is there any solution to this problem? Thanks, Adeel Rehman.

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• Draw LINE_STRIP with Unity

  - by Boozzz

  For a new project I am thinking about whether to use OpenGL or Unity3d. I have a bit of experience with OpenGL, but I am completely new to Unity. I already read through the Unity documentation and tutorials on the Unity Website. However, I could not find a way to draw a simple Line-Strip with Unity. In the following example (C#, OpenGL/SharpGL) I draw a round trajectory from a predifined point to an obstacle, which can be imagined as a divided circle with midpoint [cx,cy] and radius r. The position (x-y coordinates) of the obstacle is given by obst_x and obst_y. Question 1: How could I do the same with Unity? Question 2: In my new project, I will have to draw quite a lot of such geometric primitives. Does it make any sense to use Unity for those things? void drawCircle(float cx, float cy, float r, const float obst_x, const float obst_y) { float theta = 0.0f, pos_x, pos_y, dist; const float delta = 0.1; glBegin(GL_LINE_STRIP); while (theta < 180) { theta += delta; //get the current angle float x = r * cosf(theta); //calculate the x component float y = r * sinf(theta); //calculate the y component pos_x = x + cx; //calculate current x position pos_y = y + cy; //calculate current y position //calculate distance from current vertex to obstacle dist = sqrt(pow(pos_x - obst_x) + pow(pos_y - obst_y)); //check if current vertex intersects with obstacle if dist <= 0 { break; //stop drawing circle } else { glVertex2f(pos_x, pos_y); //draw vertex } } glEnd(); }

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• Make winform run away from the mouse.

  - by JACK IN THE CRACK

  Okay so I'm trying to make a little gag program that will "run away" from the mouse. So, to get the mouse coordinates for the whole screen and not just the form control I had to create a little helper: static class MouseHelper { [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)] internal static extern bool GetCursorPos(ref Point pt); public static Point GetPosition() { Point w32Mouse = new Point(); GetCursorPos(ref w32Mouse); return w32Mouse; } } Now I thought I was going to use the MouseMove event... but that doesn't work for outside the form control either so I have an auto-enabled timer on a 10ms loop called timerMouseMove. public partial class Form1 : Form { public Form1() { InitializeComponent(); } private bool CollisionCheck() { Point win32Mouse = MouseHelper.GetPosition(); if (win32Mouse.X <= Location.X || win32Mouse.X >= (Location.X + Width)) return false; if (win32Mouse.Y <= Location.Y || win32Mouse.Y >= (Location.Y + Height)) return false; return true; } private void timerMouseMove_Tick(object sender, EventArgs e) { if (CollisionCheck()) Location = new Point(Location.X + 1, Location.Y + 1); } } So this works out nicely, at least I have the collision checking working and whatnot. But now, how should I go about figuring which side of the form the mouse has collided with, so that I can update its location to move in the opposite direction the mouse collides with it? And such halp

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• Hibernate Mapping Annotation Question?

  - by paddydub

  I've just started using hibernate and I'm trying to map walking distance between two coordinates into a hashmap, There can be many connections from one "FromCoordinate" to another "ToCoordinate". I'm not sure if i've implemented this correctly, What annotations do i need to map this MashMap? Thanks @Entity @Table(name = "COORDCONNECTIONS") public class CoordinateConnection implements Serializable{ private static final long serialVersionUID = -1624745319005591573L; /** auto increasing id number */ @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "ID") @id private int id; @Embedded public FromCoordinate fromCoord; @Embedded public ToCoordinate toCoord; HashMap<Coordinate, ArrayList<Coordinate>> coordWalkingConnections = new HashMap<Coordinate, ArrayList<Coordinate>>(); } public class FromCoordinate implements ICoordinate { @Column(name = "FROM_LAT") private double latitude; @Column(name = "FROM_LNG") private double longitude; } public class ToCoordinate implements ICoordinate { @Column(name = "TO_LAT") private double latitude; @Column(name = "TO_LNG") private double longitude; @Column(name = "DISTANCE") private double distance; } DATABASE STRUCTURE id FROM_LAT FROM_LNG TO_LAT TO_LNG Dist 1 43.352669 -6.264341 43.350012 -6.260653 0.38 2 43.352669 -6.264341 43.352669 -6.264341 0.00 3 46.352669 -6.264341 43.353373 -6.262013 0.17 4 47.352465 -6.265865 43.351290 -6.261200 0.25 5 45.452578 -6.265768 43.352788 -6.264396 0.01 6 45.452578 -6.265768 45.782788 -6.234523 0.01 ..... ... . Example HashMap for HashMap<Coordinate, ArrayList<Coordinate>> <KEY{43.352669 -6.264341}, Arraylist VALUES{(43.350012,-6.260653,0.383657), (43.352669, -6.264341, 0.000095), (43.353373, -6.262013, 0.173201)}> <KEY{47.352465 -6.265865}, Arraylist VALUES{(43.351290,-6.261200,0.258781)}> <KEY{45.452578 -6.265768}, Arraylist VALUES{(43.352788,-6.264396,0.013726),(45.782788,-6.234523,0.017726)}>

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• Help with mysql sum and group query and managing jquery graph results.

  - by Scarface

  Hey guys, I have a system I am trying to design that will retrieve information from a database, so that it can be plotted in a jquery graph. I need to retrieve the information and somehow put it in the necessary format (for example two coordinates var d = [[1269417600000, 10],[1269504000000, 15]];). My table that I am selecting from is a table that stores user votes with fields: points_id (1=vote up ,2=vote down), user_id, timestamp, and topic_id. What I need to do is select all the votes and somehow group them into respective days and then sum the difference between 1 votes and 2 votes for each day. I then need to somehow display the data in the appropriate plotting format shown earlier. For example April 1, 4 votes. The data needs to be separated by commas, except the last plot entry, so I am not sure how to approach that. I showed an example below of the kind of thing I need but it is not correct, echo "var d=["; $query=mysql_query("SELECT *, SUM(IF(points_id = \"1\", 1,0))-SUM(IF([points_id = \"2\", 1,0)) AS 'total' FROM points LEFT JOIN topic on topic.topic_id=points.topic_id WHERE topic.creator='$user' GROUP by timestamp HAVING certain time interval"); while ($row=mysql_fetch_assoc($query)){ $timestamp=$row['timestamp']; $votes=$row['total']; echo "[$timestamp,$vote],"; } echo "];";

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• UIView frame origin doesn't set good

  - by Infinity

  Hi guys! Here is my code: frame = _pageContentView.frame; NSLog(@"%f; %f; %f; %f;", frame.origin.x, frame.origin.y, frame.size.width, frame.size.height); frame.size.height = pageContentView.frame.size.height; NSLog(@"%f; %f; %f; %f;", frame.origin.x, frame.origin.y, frame.size.width, frame.size.height); _pageContentView.frame = frame; NSLog(@"%f; %f; %f; %f;", _pageContentView.frame.origin.x, _pageContentView.frame.origin.y, _pageContentView.frame.size.width, _pageContentView.frame.size.height); And the NSLog outputs these values: 0.000000; 0.000000; 317.648956; 0.000000; 0.000000; 0.000000; 317.648956; 768.000000; 0.000007; 0.000004; 317.648956; 768.000000; Can you see? In the last row the x and y coordinates are a bit crazy... Where do these number come frome? What's the problem here?

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• event.clientX is readonly?

  - by Duracell

  Working in IE 8, mostly, but trying to write a portable solution for modern browsers. Using telerik controls. I'm catching the 'Showing' client-side event of the RadContextMenu and trying to adjust it's coordinates. The clientX, clientY and x,y members of the DOM event cannot be assigned a new value. Visual Studio breaks with a "htmlfile: Member not found" error. My goal is to get a RadContextMenu to show inside a RadEditor when the user clicks in it (under certain conditions, this is a requirement from management). So I capture the onclick event for the RadEditor's content area (radEditor.get_document().body;). I then call show(evt) on the context menu, where 'evt' is the event object corresponding to the click event. Because the RadEditor's content is in an IFRAME, you have to adjust the position of the click event before the context menu displays. This is done in the "Showing" event. However, I cannot assign a value to the members .clientX and friends. It's as if javascript has temporarily forgotten about integer + and += operators. Is it possible that these members have become readonly/const at some point? var evt = args.get_domEvent(); while (node) { evt.clientX += node.offsetLeft; //'Member not found' here. evt.clientY += node.offsetTop; node = node.offsetParent; } evt.clientY += sender.get_element().clientHeight;

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• ActionScript - clicking and determining the sprite's class

  - by TheDarkIn1978

  i'd like to add all or most of my mouse events to stage, but in order to do that i need to be able to tell what is the type of the sprite being clicked. i've added two sprites to the display list, one of which is from a class called Square, the other from a class called Circle. var mySquare:Sprite = new Square(); var myCircle:Sprite = new Circle(); addChild(mySquare); addChild(myCircle); now when i click on these sprites, i'd like to know from which class they are from, or which type of sprite it is. //mousePoint returns mouse coordinates of the stage var myArray:Array = stage.getObjectsUnderPoint(mousePoint()); if (myArray[myArray.length - 1] is Sprite) ... so far i know how to do is determine if it IS a sprite display object, but since i'll only be working with sprites i need something more specific. rather than checking "is Sprite", is there a way i can check "is Square" or "is Circle"? if (myArray[myArray.length - 1] is Square)

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• Core data setReturnsDistinctResult not working

  - by Moze

  So i'm building a small application, it uses core data database of ~25mb size with 4 entities. It's for bus timetables. In one table named "Stop" there are have ~1300 entries of bus stops with atributes "name", "id", "longitude", "latitude" and couple relationships. Now there are many stops with same name but different coordinates and id. Search is implemented using NSPredicate. So I want to show all distinct stop names in table view, i'm using setReturnsDistinctResults with NSDictionaryResultType and setPropertiesToFetch. But setReturnsDistinctResult is not working and I'm still getting all entries. Heres code: - (NSFetchRequest *)fetchRequest { if (fetchRequest == nil) { fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Stop" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; NSArray *sortDescriptors = [NSArray arrayWithObject:[[[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES] autorelease]]; [fetchRequest setSortDescriptors:sortDescriptors]; [fetchRequest setResultType:NSDictionaryResultType]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:[[entity propertiesByName] objectForKey:@"name"]]]; [fetchRequest setReturnsDistinctResults:YES]; DebugLog(@"fetchRequest initialized"); } return fetchRequest; } ///////////////////// - (NSFetchedResultsController *)fetchedResultsController { if (self.predicateString != nil) { self.predicate = [NSPredicate predicateWithFormat:@"name CONTAINS[cd] %@", self.predicateString]; [self.fetchRequest setPredicate:predicate]; } else { self.predicate = nil; [self.fetchRequest setPredicate:predicate]; } fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:self.fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:sectionNameKeyPath cacheName:nil]; return fetchedResultsController; } ////////////// - (UITableViewCell *)tableView:(UITableView *)table cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } cell.textLabel.text = [[fetchedResultsController objectAtIndexPath:indexPath] valueForKey:@"name"]; return cell; }

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• Calculating bounding box a certain distance away from a lat/long coordinate in Java

  - by Bryce Thomas

  Given a coordinate (lat, long), I am trying to calculate a square bounding box that is a given distance (e.g. 50km) away from the coordinate. So as input I have lat, long and distance and as output I would like two coordinates; one being the south-west (bottom-left) corner and one being the north-east (top-right) corner. I have seen a couple of answers on here that try to address this question in Python, but I am looking for a Java implementation in particular. Just to be clear, I intend on using the algorithm on Earth only and so I don't need to accommodate a variable radius. It doesn't have to be hugely accurate (+/-20% is fine) and it'll only be used to calculate bounding boxes over small distances (no more than 150km). So I'm happy to sacrifice some accuracy for an efficient algorithm. Any help is much appreciated. Edit: I should have been clearer, I really am after a square, not a circle. I understand that the distance between the center of a square and various points along the square's perimeter is not a constant value like it is with a circle. I guess what I mean is a square where if you draw a line from the center to any one of the four points on the perimeter that results in a line perpendicular to a side of the perimeter, then those 4 lines have the same length.

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• Matlab - Propagate points orthogonally on to the edge of shape boundaries

  - by Graham

  Hi I have a set of points which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. I want to cast a ray from each point from the set of points in an orthogonal direction and detect at which point it intersects the shape boundary at. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking orthogonal unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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• Android maps out of memory error

  - by SamB09

  Hi , sometimes when running a google maps program with an overlay image i will receive a bit map out of memory error. It always seems to be at a random point in the app. Im not sure how to solve this. Anyone have any ideas ? My overlay code is below , im not sure if you need to see the class its called in though? public class MyOverlay2 extends Overlay { private static final double MAX_TAP_DISTANCE_KM = 3; // Rough approximation - one degree = 50 nautical miles private static final double MAX_TAP_DISTANCE_DEGREES = MAX_TAP_DISTANCE_KM * 0.5399568 * 50; private final GeoPoint gPoint; private final Context cont; private final int draw; // private final int lat; public MyOverlay2(Context cont, GeoPoint gPoint1, int draw) { // constructor will be called in the userLocation class to draw an overly image this.cont = cont; this.gPoint = gPoint1; this.draw = draw; } @Override public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) { // constructor takes 3 arguments super.draw(canvas, mapView, shadow); // Convert geo coordinates to screen pixels Point screenPoint = new Point(); mapView.getProjection().toPixels(gPoint, screenPoint); //Read the image from the xml resource using a bitmap factory BitmapFactory.Options options=new BitmapFactory.Options(); options.inSampleSize = 1; Bitmap preview_bitmap=BitmapFactory.decodeResource(cont.getResources(),R.drawable.monday12,options); //draw the image at the location specified by the co-ordinates canvas.drawBitmap(preview_bitmap, screenPoint.x - preview_bitmap.getWidth() /2, screenPoint.y - preview_bitmap.getHeight()/2 , null); // get the images height and width values divided by two draw the image at the specified screen points return true; } @Override public boolean onTap(GeoPoint s, MapView mapView) { // Handle tapping on the overlay here return true; } }

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• Dealing with Imprecise Drawing in CAD Drawing

  - by Graviton

  I have a CAD application, that allows user to draw lines and polygons and all that. One thorny problem that I face is user drawing can be highly imprecise, for example, a user might want to draw two rectangles that are connected to each other. Hence there should be one line shared by two rectangles. However, it's easy for user to, instead of draw a line, draw two lines that are very close to each other, so close to each other that when look from the screen, you would be mistaken that they are the same line, except that they aren't when you zoom in a little bit. My application would require user to properly draw the lines ( or my preprocessing must be able to do auto correction), or else my internal algorithm would not be able to process the inputs correctly. What is the best strategy to combat this kind of problem? I am thinking about rounding the point coordinates to a certain degree of precision, but although I can't exactly pinpoint the problem of this approach, but I feel that this is not the correct way of doing things, that this will introduce a new set of problem. Any idea?

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• How to draw a circle in java with a radius and points around the edge

  - by windopal

  Hi, I'm really stuck on how to go about programming this. I need to draw a circle within a JFrame with a radius and points around the circumference. i can mathematically calculate how to find the coordinates of the point around the edge but i cant seem to be able to program the circle. I am currently using a Ellipse2D method but that doesn't seem to work and doesn't return a radius, as under my understanding, it doesn't draw the circle from the center rather from a starting coordinate using a height and width. My current code is on a separate frame but i need to add it to my existing frame. import java.awt.*; import javax.swing.*; import java.awt.geom.*; public class circle extends JFrame { public circle() { super("circle"); setSize(410, 435); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Panel sp = new Panel(); Container content = getContentPane(); content.add(sp); setContentPane(content); setVisible(true); } public static void main (String args[]){ circle sign = new circle(); } } class Panel extends JPanel { public void paintComponent(Graphics comp) { super.paintComponent(comp); Graphics2D comp2D = (Graphics2D) comp; comp2D.setColor(Color.red); Ellipse2D.Float sign1 = new Ellipse2D.Float(0F, 0F, 350F, 350F); comp2D.fill(sign1); } }

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• How do I draw the points in an ESRI Polyline, given the bounding box as lat/long and the "points" as

  - by Aaron

  I'm using OpenMap and I'm reading a ShapeFile using com.bbn.openmap.layer.shape.ShapeFile. The bounding box is read in as lat/long points, for example 39.583642,-104.895486. The bounding box is a lower-left point and an upper-right point which represents where the points are contained. The "points," which are named "radians" in OpenMap, are in a different format, which looks like this: [0.69086486, -1.8307719, 0.6908546, -1.8307716, 0.6908518, -1.8307717, 0.69085056, -1.8307722, 0.69084936, -1.8307728, 0.6908477, -1.8307738, 0.69084626, -1.8307749, 0.69084185, -1.8307792]. How do I convert the points like "0.69086486, -1.8307719" into x,y coordinates that are usable in normal graphics? I believe all that's needed here is some kind of conversion, because bringing the points into Excel and graphing them creates a line whose curve matches the curve of the road at the given location (lat/long). However, the axises need to be adjusted manually and I have no reference as how to adjust the axises, since the given bounding box appears to be in a different format than the given points. The ESRI Shapefile technical description doesn't seem to mention this (http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf).

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• Google Maps, marker info window won't show up ?

  - by user296516

  Hi guys, I have written this code that loops through an array of lat/long coordinates and places a marker at each of the coordinate. Everything forks fine, exempt the info window won't appear once the marker is clicked. var ExpTowerIcon = new GIcon(); ExpTowerIcon.image = "tower.png"; ExpTowerIcon.iconSize = new GSize(75, 75); ExpTowerIcon.iconAnchor = new GPoint(37, 65); ExpTowerIcon.infoWindowAnchor = new GPoint(37, 20); var marker=new Array(); for ( i=0 ; i < lat.length ; i++ ) { var MarkerPoint = new GLatLng(lat[i],long[i]); marker[i] = new GMarker(MarkerPoint,{icon:ExpTowerIcon}) map.addOverlay( marker[i] ); GEvent.addListener( marker[i] , 'click', function() { marker[i].openInfoWindowHtml('Hello!') ; }); var polyline = new GPolyline([ new GLatLng(lat[i],long[i]) , new GLatLng(lat[i+1],long[i+1]) ], "#ff0000", 5); map.addOverlay(polyline); } Any ideas? Thanks!

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