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

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