IRawPixels Interface

Provides access to members that control pixel reading and writing from a RasterBand.

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Members

	Name	Description
	AcquireCache	Gets reference to edit cache.
	CreatePixelBlock	Allocates a PixelBlock of size requested and type of this band.
	NumCacheRefs	Number of outstanding cache references
	Read	Read a block of pixels starting from tlc (top left corner).
	ReturnCache	Restores edit cache to previous state.
	Write	Write a block of pixels starting from tlc (top left corner).

Classes that implement IRawPixels

Remarks

When using a PixelBlock created by the RasterBand coclass, use only the first plane because the RasterBand is a single band. All formats can be read using this technique, but only GRID, TIFF, Imagine, BIL, BIP, and BSQ formats can be written. Reading the PixelBlock from the band completes the initialization of the PixelBlock and should be done before writing to the band.

The Read method reads a block of pixels into the input PixelBlock object. The data is read beginning at a specified pixel location. This pixel location is the offset from the top-left corner of the image, represented by (0,0), and increases down and to the right.

The Write method outputs the contents of a PixelBlock to the RasterBand. The PixelBlock is written to an area in the band specified by its top-left corner in the same pixel coordinate space used by the Read method. If transactioning is enabled, this write is persisted temporarily to a memory cache that allows undo support; otherwise, the data is persisted directly to disk at this time.

The AcquireCache and ReturnCache methods control a cache within the band object that allows the transactioning mechanism used by the RasterBand to be activated.