我目前正在创建一个应用程序，该应用程序需要在地图上绘制大量不同大小的叠加层。该应用程序当前抓取 2 个地图点，这些地图点代表覆盖层应位于的边界框的角。然后我将这些转换为 MKMapRect 以在 MKOverlay 类中使用。叠加层绘制在正确的位置，但图像似乎垂直翻转，当我尝试应用 CGAffineTransformMakeRotation(180) 时，我可以看出这一点，图像出现在正确的位置，但书写是倒退的。
如果有人可以帮助我弄清楚它为什么这样做，将不胜感激，请参阅下面的代码。
设置代码：
// First grab the overlay co-ordinates
double left = [[self.storedWildMapObject.arrayBBox objectAtIndex:0] doubleValue], bottom = [[self.storedWildMapObject.arrayBBox objectAtIndex:1] doubleValue], right = [[self.storedWildMapObject.arrayBBox objectAtIndex:2] doubleValue], top = [[self.storedWildMapObject.arrayBBox objectAtIndex:3] doubleValue];
// Store these in 2 coordinates representing top left / bot right
CLLocationCoordinate2D upperLeftCoord =
CLLocationCoordinate2DMake(top,left);
CLLocationCoordinate2D lowerRightCoord =
CLLocationCoordinate2DMake(bottom,right);
//Convert to map points
MKMapPoint upperLeft = MKMapPointForCoordinate(upperLeftCoord);
MKMapPoint lowerRight = MKMapPointForCoordinate(lowerRightCoord);
// Work out sizes
double rightToLeftDiff = lowerRight.y - upperLeft.y;
double topToBottDiff = lowerRight.x - upperLeft.x;
MKMapRect bounds = MKMapRectMake(upperLeft.x, upperLeft.y, topToBottDiff, rightToLeftDiff);
// Add to overlay
MKMapOverlay *mapOverlay = [[MKMapOverlay alloc] initWithMapRect:bounds andCoord:upperLeftCoord];
[self.mapV addOverlay:mapOverlay];
// 地图叠加
- (id)initWithMapRect:(MKMapRect)rect andCoord:(CLLocationCoordinate2D)coord
{
self = [super init];
if (self)
{
self.centerPos = coord;
self.mkMapRect = rect;
}
return self;
}
-(CLLocationCoordinate2D)coordinate
{
return self.centerPos;
}
- (MKMapRect)boundingMapRect
{
return self.mkMapRect;
}
// MapOverlayView
- (id)initWithOverlay:(id <MKOverlay>)overlay andImage:(UIImage *)img
{
self = [super initWithOverlay:overlay];
if (self)
{
self.image = img;
}
return self;
}
/** Degrees to Radian **/
#define degreesToRadians( degrees ) ( ( degrees ) / 180.0 * M_PI )
/** Radians to Degrees **/
#define radiansToDegrees( radians ) ( ( radians ) * ( 180.0 / M_PI ) )
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)ctx
{
CGImageRef imageReference = self.image.CGImage;
MKMapRect theMapRect = [self.overlay boundingMapRect];
CGRect theRect = [self rectForMapRect:theMapRect];
CGRect clipRect = [self rectForMapRect:mapRect];
CGContextAddRect(ctx, clipRect);
CGContextClip(ctx);
//CGContextRotateCTM(ctx, degreesToRadians(180.0f));
CGContextDrawImage(ctx, theRect, imageReference);
}
以防万一它有助于我也有一个调试器打印出 MapOverlayView 中使用的 MapRect：
(lldb) p theMapRect
(MKMapRect) $17 = {
(MKMapPoint) origin = {
(double) x = 1.27662e+08
(double) y = 7.86099e+07
}
(MKMapSize) size = {
(double) width = 8.12378e+06
(double) height = 1.27474e+07
}
}
下面是它的样子：
