The IDLgrImage::DeleteTileData procedure method removes tile data from the cache. This is useful to free up cache memory if the application knows a number of tiles will not be displayed again for some time. It could also be used if the image data changes and the old image data should be removed from the cache. If you remove a tile from the cache, a subsequent invocation of QueryRequiredTiles returns the tile if it is visible.
This method deletes tiles even if they were loaded with the NO_FREE keyword set. An error is generated if the tile argument does not specify a valid tile or the level argument specifies an invalid level. If the tile being deleted doesn’t have any tile data, no error will be generated.
Syntax
Obj->[IDLgrImage::]DeleteTileData, TileInfo [, /ALL]
Arguments
TileInfo
A named structure describing the tile or tiles for which the data is being deleted. This structure contains the following fields:
|
Field |
Data Type |
Description |
|
X |
Long |
The horizontal position of the left side of the tile(s) measured from the left of the image in pixels.
|
|
Y |
Long |
The vertical position of the bottom of the tile(s) measured from the bottom of the image in pixels.
|
|
WIDTH |
Long |
The width of the tile(s) in pixels.
|
|
HEIGHT |
Long |
The height of the tile(s) in pixels.
|
|
LEVEL |
Long |
The data resolution, where 0 is the full resolution image. A value of n (n > 0) indicates that the resolution is half that of the n-1 level.
|
|
DEST |
OBJREF |
The object reference to the destination object that is displaying the tiled IDLgrImage.
|
If a number of tiles are to be deleted by passing a region covering multiple tiles then X, Y, WIDTH and HEIGHT must be multiples of the tile size.
Keywords
ALL
Set this keyword to delete all tiles at all levels in the cache for this image. This is useful for clearing the cache when image data changes and new data will be loaded.
The new tile data may now have a different interleave format and number of channels than any tiles previously stored in the object. See IDLgrImage::SetTileData.
Note: The TileInfo structure must still be passed, and must contain a valid destination object reference in the Dest field. The other entries can be 0 in this case.
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