zmap_tile_GetDataPtr

Retrieve the raw memory pointer to the data block of a mosaic tile.

void* zmap_tile_GetDataPtr(void* hTile);

A null pointer if:

• The tile handle is invalid.
• The tile has not been locked for use via zmap_tile_SetLock (this is automatic when loading/saving tiles).

A valid non-null pointer otherwise.

Pixels are ordered in rows going east-to-west, with rows ordered south to north. To convert from x/y coordinate to memory offset, use the following formula:

long offset = (x + TileSize * y) * PixelMemSize;

…where PixelMemSize is the size in memory of one pixel (see zmap_GetPixelSize).

To convert from memory offsets to pixel coordinates, use the following formulae:

long x = (offset/PixelMemSize)%TileSize;
long y = (offset/PixelMemSize)/TileSize;

It is recommended that, wherever possible, the zmap_tile_GetPixel /zmap_tile_SetPixel functions are used for accessing tile data, instead of direct memory access with zmap_tile_GetDataPtr. Those functions include coordinate checking and memory protection, as well has handling mip-mapping and mosaic tile cache loading/saving automatically.