cache_view - Low-level access to image pixels with multiple views

- NAME
- SYNOPSIS
- FUNCTION DESCRIPTIONS

- AcquireCacheView
- CloseCacheView
- GetCacheView
- GetCacheViewIndexes
- GetCacheViewPixels
- OpenCacheView
- SetCacheView
- SyncCacheView

# NAME

cache_view - Low-level access to image pixels with multiple views

# SYNOPSIS

const PixelPacket * AcquireCacheView( const ViewInfo *view, const long x, const long y, const unsigned long columns, const unsigned long rows, ExceptionInfo *exception );

void CloseCacheView( ViewInfo *view );

PixelPacket * GetCacheView( ViewInfo *view, const long x, const long y, const unsigned long columns, const unsigned long rows );

IndexPacket * GetCacheViewIndexes( const ViewInfo *view );

PixelPacket * GetCacheViewPixels( const ViewInfo *view );

ViewInfo * OpenCacheView( Image *image );

PixelPacket * SetCacheView( ViewInfo *view, const long x, const long y, const unsigned long columns, const unsigned long rows );

unsigned int SyncCacheView( ViewInfo *view );

# FUNCTION DESCRIPTIONS

## AcquireCacheView

Method AcquireCacheView gets pixels from the in-memory or disk pixel cache as defined by the geometry parameters. A pointer to the pixels is returned if the pixels are transferred, otherwise a NULL is returned.

The format of the AcquireCacheView method is:

> const PixelPacket *AcquireCacheView ( const ViewInfo *view, const long x, const long y, const unsigned long columns, const unsigned long rows, ExceptionInfo *exception );

A description of each parameter follows:

pixels:

  Method GetCacheView returns a null pointer if an error occurs, otherwise a pointer to the view pixels.

view:

  The address of a structure of type ViewInfo.

x,y,columns,rows:

  These values define the perimeter of a region of pixels.

exception:

  Return any errors or warnings in this structure.

## CloseCacheView

> CloseCacheView() closes the specified view returned by a previous call to OpenCacheView ( ) .

The format of the CloseCacheView method is:

> void CloseCacheView ( ViewInfo *view );

A description of each parameter follows:

view:

  The address of a structure of type ViewInfo.

## GetCacheView

> GetCacheView() gets pixels from the in-memory or disk pixel cache as defined by the geometry parameters. A pointer to the pixels is returned if the pixels are transferred, otherwise a NULL is returned.

The format of the GetCacheView method is:

> PixelPacket *GetCacheView ( ViewInfo *view, const long x, const long y, const unsigned long columns, const unsigned long rows );

A description of each parameter follows:

pixels:

  Method GetCacheView returns a null pointer if an error occurs, otherwise a pointer to the view pixels.

view:

  The address of a structure of type ViewInfo.

x,y,columns,rows:

  These values define the perimeter of a region of pixels.

## GetCacheViewIndexes

Method GetCacheViewIndexes returns the indexes associated with the specified view.

The format of the GetCacheViewIndexes method is:

> IndexPacket *GetCacheViewIndexes ( const ViewInfo *view );

A description of each parameter follows:

indexes:

  Method GetCacheViewIndexes returns the indexes associated with the specified view.

view:

  The address of a structure of type ViewInfo.

## GetCacheViewPixels

> GetCacheViewPixels() returns the pixels associated with the specified specified view.

The format of the GetCacheViewPixels method is:

> PixelPacket *GetCacheViewPixels ( const ViewInfo *view );

A description of each parameter follows:

view:

  The address of a structure of type ViewInfo.

## OpenCacheView

> OpenCacheView() opens a view into the pixel cache.

The format of the OpenCacheView method is:

> ViewInfo *OpenCacheView ( Image *image );

A description of each parameter follows:

image:

  The image.

## SetCacheView

> SetCacheView() gets pixels from the in-memory or disk pixel cache as defined by the geometry parameters. A pointer to the pixels is returned if the pixels are transferred, otherwise a NULL is returned.

The format of the SetCacheView method is:

> PixelPacket *SetCacheView ( ViewInfo *view, const long x, const long y, const unsigned long columns, const unsigned long rows );

A description of each parameter follows:

view:

  The address of a structure of type ViewInfo.

x,y,columns,rows:

  These values define the perimeter of a region of pixels.

## SyncCacheView

> SyncCacheView() saves the view pixels to the in-memory or disk cache. The method returns True if the pixel region is synced, otherwise False.

The format of the SyncCacheView method is:

> unsigned int SyncCacheView ( ViewInfo *view );

A description of each parameter follows:

view:

  The address of a structure of type ViewInfo.