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在给定的纬度和经度处从 MKMapView 生成 UIImage

发布于 2024-10-29 21:50:26 字数 229 浏览 2 评论 0原文

我有一个使用 MKMapView 来显示地图的应用程序。我还有一个 UITableView，它在每行的左侧显示地图的一个小片段图像。它看起来像这样：

在此处输入图像描述

我希望能够在 MKMapView 的左侧生成该图像。尺寸为 40x40。我知道给定的纬度和经度是我想要获取图像的特定位置的中心。我该怎么做？

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你在看孤独的风景 2024-11-05 21:50:26

要获取视图的快照：

-(UIImage *)pictureForView:(UIView*)view
{
    UIGraphicsBeginImageContext(view.frame.size);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    [view.layer renderInContext:ctx];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
    return image;
}

这是整个视图 - 您需要从中雕刻出您需要的部分。或者也许只是将地图视图集中在您需要的位置上并进行最大缩放。然后，当将整个视图的图片调整为缩略图大小时，可能就足够了。

要将地图图像裁剪到所需位置：

UIImage* mapImage = [self pictureForView:self.mapView];
MKCoordinateRegion mapRegion = self.mapView.region;
//pointOfInterest is assumed to be on the map view, e.g. get the coordinate of the pin
CLLocationCoordinate2D pointOfInterest = ????;

double mapLatFrom = mapRegion.center.latitude - mapRegion.span.latitudeDelta/2;
double mapLonFrom = mapRegion.center.longitude - mapRegion.span.longitudeDelta/2;

double cropX = ((pointOfInterest.latitude - mapLatFrom)/mapRegion.span.latitudeDelta)*mapView.frame.size.width - self.imageView.frame.size.width /2;
double cropY = ((pointOfInterest.longitude - mapLonFrom)/mapRegion.span.longitudeDelta)*mapView.frame.size.height - self.imageView.frame.size.height /2;

CGRect cropRect = CGRectMake(cropX, cropY, self.imageView.frame.size.width, self.imageView.frame.size.height);
CGImageRef imageRef = CGImageCreateWithImageInRect([mapImage CGImage], cropRect);

self.imageView.image = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);

To get a snapshot of a view:

-(UIImage *)pictureForView:(UIView*)view
{
    UIGraphicsBeginImageContext(view.frame.size);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    [view.layer renderInContext:ctx];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
    return image;
}

That's for the whole view - you'll need to carve the piece you need out of it. Or maybe just center the map view on the location you need and do the maximum zoom. Then the picture of the whole view, when resized to a thumbnail size, might be just good enough.

To crop the map image to the desired location:

UIImage* mapImage = [self pictureForView:self.mapView];
MKCoordinateRegion mapRegion = self.mapView.region;
//pointOfInterest is assumed to be on the map view, e.g. get the coordinate of the pin
CLLocationCoordinate2D pointOfInterest = ????;

double mapLatFrom = mapRegion.center.latitude - mapRegion.span.latitudeDelta/2;
double mapLonFrom = mapRegion.center.longitude - mapRegion.span.longitudeDelta/2;

double cropX = ((pointOfInterest.latitude - mapLatFrom)/mapRegion.span.latitudeDelta)*mapView.frame.size.width - self.imageView.frame.size.width /2;
double cropY = ((pointOfInterest.longitude - mapLonFrom)/mapRegion.span.longitudeDelta)*mapView.frame.size.height - self.imageView.frame.size.height /2;

CGRect cropRect = CGRectMake(cropX, cropY, self.imageView.frame.size.width, self.imageView.frame.size.height);
CGImageRef imageRef = CGImageCreateWithImageInRect([mapImage CGImage], cropRect);

self.imageView.image = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);

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