Get all X,Y coordinates between two points in objective C - ios

Question

How to get all X,Y coordinates between two points.
I want to move a UIButton in a diagonal pattern in objective C.
Example. To move UIButton from position 'Point A' towards position 'Point B'.
.Point B
. Point A
Thanks in advance.

Answer 1

you can use Bresenham's line algorithm
Here is a slightly simplified version, I have used a bunch of times
+(NSArray*)getAllPointsFromPoint:(CGPoint)fPoint toPoint:(CGPoint)tPoint
{
/*Simplified implementation of Bresenham's line algoritme */
NSMutableArray *ret = [NSMutableArray array];
float deltaX = fabsf(tPoint.x - fPoint.x);
float deltaY = fabsf(tPoint.y - fPoint.y);
float x = fPoint.x;
float y = fPoint.y;
float err = deltaX-deltaY;
float sx = -0.5;
float sy = -0.5;
if(fPoint.x<tPoint.x)
sx = 0.5;
if(fPoint.y<tPoint.y)
sy = 0.5;
do {
[ret addObject:[NSValue valueWithCGPoint:CGPointMake(x, y)]];
float e = 2*err;
if(e > -deltaY)
{
err -=deltaY;
x +=sx;
}
if(e < deltaX)
{
err +=deltaX;
y+=sy;
}
} while (round(x) != round(tPoint.x) && round(y) != round(tPoint.y));
[ret addObject:[NSValue valueWithCGPoint:tPoint]];//add final point
return ret;
}
If you simply want to animate a UIControl from one location to another, you might want to use UIAnimation:
[UIView animateWithDuration:1.0f delay:0.0f options:UIViewAnimationOptionCurveLinear animations:^{
btn.center = CGPointMake(<NEW_X>, <NEW_Y>)
} completion:^(BOOL finished) {
}];

Answer 2

You should really use Core Animation for this. You just need to specify the new origin for your UIButton and Core Animation does the rest:
[UIView animateWithDuration:0.3 animations:^{
CGRect frame = myButton.frame;
frame.origin = CGPointMake(..new X.., ..new Y..);
myButton.frame = frame;
}];

Answer 3

For Swift 3.0,
func findAllPointsBetweenTwoPoints(startPoint : CGPoint, endPoint : CGPoint) {
var allPoints :[CGPoint] = [CGPoint]()
let deltaX = fabs(endPoint.x - startPoint.x)
let deltaY = fabs(endPoint.y - startPoint.y)
var x = startPoint.x
var y = startPoint.y
var err = deltaX-deltaY
var sx = -0.5
var sy = -0.5
if(startPoint.x<endPoint.x){
sx = 0.5
}
if(startPoint.y<endPoint.y){
sy = 0.5;
}
repeat {
let pointObj = CGPoint(x: x, y: y)
allPoints.append(pointObj)
let e = 2*err
if(e > -deltaY)
{
err -= deltaY
x += CGFloat(sx)
}
if(e < deltaX)
{
err += deltaX
y += CGFloat(sy)
}
} while (round(x) != round(endPoint.x) && round(y) != round(endPoint.y));
allPoints.append(endPoint)
}

Answer 4

This version of Bresenham's line algorithm works well with horizontal line:
+ (NSArray*)getAllPointsFromPoint:(CGPoint)fPoint toPoint:(CGPoint)tPoint {
/* Bresenham's line algorithm */
NSMutableArray *ret = [NSMutableArray array];
int x1 = fPoint.x;
int y1 = fPoint.y;
int x2 = tPoint.x;
int y2 = tPoint.y;
int dy = y2 - y1;
int dx = x2 - x1;
int stepx, stepy;
if (dy < 0) { dy = -dy; stepy = -1; } else { stepy = 1; }
if (dx < 0) { dx = -dx; stepx = -1; } else { stepx = 1; }
dy <<= 1; // dy is now 2*dy
dx <<= 1; // dx is now 2*dx
[ret addObject:[NSValue valueWithCGPoint:CGPointMake(x1, y1)]];
if (dx > dy)
{
int fraction = dy - (dx >> 1); // same as 2*dy - dx
while (x1 != x2)
{
if (fraction >= 0)
{
y1 += stepy;
fraction -= dx; // same as fraction -= 2*dx
}
x1 += stepx;
fraction += dy; // same as fraction -= 2*dy
[ret addObject:[NSValue valueWithCGPoint:CGPointMake(x1, y1)]];
}
} else {
int fraction = dx - (dy >> 1);
while (y1 != y2) {
if (fraction >= 0) {
x1 += stepx;
fraction -= dy;
}
y1 += stepy;
fraction += dx;
[ret addObject:[NSValue valueWithCGPoint:CGPointMake(x1, y1)]];
}
}
return ret;
}
UPDATE: this is actually simple math find the point on the line made out of two points, here is my algo:
+ (NSArray*)getNumberOfPoints:(int)num fromPoint:(CGPoint)p toPoint:(CGPoint)q {
NSMutableArray *ret = [NSMutableArray arrayWithCapacity:num];
float epsilon = 1.0f / (float)num;
int count = 1;
for (float t=0; t < 1+epsilon && count <= num ; t += epsilon) {
float x = (1-t)*p.x + t*q.x;
float y = (1-t)*p.y + t*q.y;
[ret addObject:[NSValue valueWithCGPoint:CGPointMake(x, y)]];
count++;
}
// DDLogInfo(#"Vector: points made: %d",(int)[ret count]);
// DDLogInfo(#"Vector: epsilon: %f",epsilon);
// DDLogInfo(#"Vector: points: %#",ret);
return [ret copy];
}