ios – 计算在“覆盖”图层之外的“过度放大”时,在MapRect中显示的图块

概述我正在使用一个使用MKOverlay视图的应用程序,在Google基础地图上叠加自己的自定义地图.我一直在使用苹果的优秀的TileMap示例代码(来自WWDC 2010)作为指导. 我的问题 – 当“过度缩放”到比我生成的图块集更深的细节水平时,代码不显示,因为在计算的Z级别没有可用的图块. 我想要的行为 – 当“超缩”应用程序应该只是继续放大最深层次的瓷砖.这是一个很好的用户体验叠加层变得模糊 我正在使用一个使用MKOverlay视图的应用程序,在Google基础地图上叠加自己的自定义地图.我一直在使用苹果的优秀的TileMap示例代码(来自WWDC 2010)作为指导.

我的问题 – 当“过度缩放”到比我生成的图块集更深的细节水平时,代码不显示,因为在计算的Z级别没有可用的图块.

我想要的行为 – 当“超缩”应用程序应该只是继续放大最深层次的瓷砖.这是一个很好的用户体验叠加层变得模糊 – 这是一个非常糟糕的体验,使覆盖消失.

这里是返回绘制图块的代码 – 我需要弄清楚如何修改它以覆盖Z深度,而不会破坏为叠加图块计算的帧的缩放.有什么想法吗？？？

- (NSArray *)tilesInMapRect:(MKMapRect)rect zoomScale:(MKZoomScale)scale{    NSInteger z = zoomScaletoZoomLevel(scale);    // PROBLEM: I need to find a way to cap z at my maximum tile directory depth.    // Number of tiles wIDe or high (but not wIDe * high)    NSInteger tilesAtZ = pow(2,z);    NSInteger minX = floor((MKMapRectGetMinX(rect) * scale) / TILE_SIZE);    NSInteger maxX = floor((MKMapRectGetMaxX(rect) * scale) / TILE_SIZE);    NSInteger minY = floor((MKMapRectGetMinY(rect) * scale) / TILE_SIZE);    NSInteger maxY = floor((MKMapRectGetMaxY(rect) * scale) / TILE_SIZE);    NSMutableArray *tiles = nil;    for (NSInteger x = minX; x <= maxX; x++) {        for (NSInteger y = minY; y <= maxY; y++) {            // As in initWithTilePath,need to flip y index            // to match the gdal2tiles.py convention.            NSInteger flippedY = abs(y + 1 - tilesAtZ);            Nsstring *tileKey = [[Nsstring alloc]                                   initWithFormat:@"%d/%d/%d",z,x,flippedY];            if ([tilePaths containsObject:tileKey]) {                if (!tiles) {                    tiles = [NSMutableArray array];                }                MKMapRect frame = MKMapRectMake((double)(x * TILE_SIZE) / scale,(double)(y * TILE_SIZE) / scale,TILE_SIZE / scale,TILE_SIZE / scale);                Nsstring *path = [[Nsstring alloc] initWithFormat:@"%@/%@.png",tileBase,tileKey];                ImageTile *tile = [[ImageTile alloc] initWithFrame:frame path:path];                [path release];                [tiles addobject:tile];                [tile release];            }            [tileKey release];        }    }    return tiles;}

FYI,这里是有人问过的zoomScaletoZoomLevel帮助器函数：

// Convert an MKZoomScale to a zoom level where level 0 contains 4 256px square tiles,// which is the convention used by gdal2tiles.py.static NSInteger zoomScaletoZoomLevel(MKZoomScale scale) {    double numTilesAt1_0 = MKMapSizeWorld.wIDth / TILE_SIZE;    NSInteger zoomLevelAt1_0 = log2(numTilesAt1_0);  // add 1 because the convention skips a virtual level with 1 tile.    NSInteger zoomLevel = MAX(0,zoomLevelAt1_0 + floor(log2f(scale) + 0.5));    return zoomLevel;}

解决方法 想象一下,覆盖层是云覆盖 – 或者在我们的情况下,是蜂窝信号覆盖.在深度放大时可能不会“看起来很好”,但覆盖层仍然向用户传达必要的信息.

我已经解决了这个问题,添加了一个OverZoom模式来增强Apple的TileMap示例代码.

这是TileOverlay.m中的新TileInMapRect函数：

- (NSArray *)tilesInMapRect:(MKMapRect)rect zoomScale:(MKZoomScale)scale{    NSInteger z = zoomScaletoZoomLevel(scale);    // OverZoom Mode - Detect when we are zoomed beyond the tile set.    NSInteger overZoom = 1;    NSInteger zoomCap = MAX_ZOOM;  // A constant set to the max tile set depth.    if (z > zoomCap) {        // overZoom progression: 1,2,4,8,etc...        overZoom = pow(2,(z - zoomCap));        z = zoomCap;    }    // When we are zoomed in beyond the tile set,use the tiles    // from the maximum z-depth,but render them larger.    NSInteger adjustedTileSize = overZoom * TILE_SIZE;    // Number of tiles wIDe or high (but not wIDe * high)    NSInteger tilesAtZ = pow(2,z);    NSInteger minX = floor((MKMapRectGetMinX(rect) * scale) / adjustedTileSize);    NSInteger maxX = floor((MKMapRectGetMaxX(rect) * scale) / adjustedTileSize);    NSInteger minY = floor((MKMapRectGetMinY(rect) * scale) / adjustedTileSize);    NSInteger maxY = floor((MKMapRectGetMaxY(rect) * scale) / adjustedTileSize);    NSMutableArray *tiles = nil;    for (NSInteger x = minX; x <= maxX; x++) {        for (NSInteger y = minY; y <= maxY; y++) {            // As in initWithTilePath,need to flip y index to match the gdal2tiles.py convention.            NSInteger flippedY = abs(y + 1 - tilesAtZ);            Nsstring *tileKey = [[Nsstring alloc] initWithFormat:@"%d/%d/%d",flippedY];            if ([tilePaths containsObject:tileKey]) {                if (!tiles) {                    tiles = [NSMutableArray array];                }                MKMapRect frame = MKMapRectMake((double)(x * adjustedTileSize) / scale,(double)(y * adjustedTileSize) / scale,adjustedTileSize / scale,adjustedTileSize / scale);                Nsstring *path = [[Nsstring alloc] initWithFormat:@"%@/%@.png",tileKey];                ImageTile *tile = [[ImageTile alloc] initWithFrame:frame path:path];                [path release];                [tiles addobject:tile];                [tile release];            }            [tileKey release];        }    }    return tiles;}

这里是TileOverlayVIEw.m中的新的drawMapRect：

- (voID)drawMapRect:(MKMapRect)mapRect          zoomScale:(MKZoomScale)zoomScale          inContext:(CGContextRef)context{    // OverZoom Mode - Detect when we are zoomed beyond the tile set.    NSInteger z = zoomScaletoZoomLevel(zoomScale);    NSInteger overZoom = 1;    NSInteger zoomCap = MAX_ZOOM;    if (z > zoomCap) {        // overZoom progression: 1,(z - zoomCap));    }    TileOverlay *tileOverlay = (TileOverlay *)self.overlay;    // Get the List of tile images from the model object for this mapRect.  The    // List may be 1 or more images (but not 0 because canDrawMapRect would have    // returned NO in that case).    NSArray *tilesInRect = [tileOverlay tilesInMapRect:mapRect zoomScale:zoomScale];    CGContextSetAlpha(context,tileAlpha);    for (ImageTile *tile in tilesInRect) {        // For each image tile,draw it in its corresponding MKMapRect frame        CGRect rect = [self rectForMapRect:tile.frame];        UIImage *image = [[UIImage alloc] initWithContentsOffile:tile.imagePath];        CGContextSaveGState(context);        CGContextTranslateCTM(context,CGRectGetMinX(rect),CGRectGetMinY(rect));        // OverZoom mode - 1 when using tiles as is,8 etc when overzoomed.        CGContextScaleCTM(context,overZoom/zoomScale,overZoom/zoomScale);        CGContextTranslateCTM(context,image.size.height);        CGContextScaleCTM(context,1,-1);        CGContextDrawImage(context,CGRectMake(0,image.size.wIDth,image.size.height),[image CGImage]);        CGContextRestoreGState(context);        // Added release here because "Analyze" was reporting a potential leak. BUG in Apple's sample code?        [image release];    }}

似乎现在工作很好

BTW – 我认为TileMap示例代码缺少一个[映像版本],并且正在泄漏内存.注意我在上面的代码中添加了它.

我希望这有助于其他一些同样的问题.

干杯,

>克里斯

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