- NAME
- SYNOPSIS
- FUNCTION DESCRIPTIONS

- AcquireImagePixels
- AcquireOnePixel
- DestroyCacheInfo
- DestroyImagePixels
- GetImagePixels
- GetImageVirtualPixelMethod
- GetIndexes
- GetOnePixel
- GetPixels
- ModifyCache
- ReferenceCache
- SetImagePixels
- SetImageVirtualPixelMethod

# NAME

cache - Get or Set Image Pixels

# SYNOPSIS

const PixelPacket * AcquireImagePixels( const Image *image, const long x, const long y, const unsigned long columns, const unsigned long rows, ExceptionInfo *exception );

PixelPacket AcquireOnePixel( const Image image, const long x, const long y, ExceptionInfo exception );

Cache DestroyCacheInfo( Cache cache );

void DestroyImagePixels( Image *image );

PixelPacket * GetImagePixels( Image *image, const long x, const long y, const unsigned long columns, const unsigned long rows );

VirtualPixelMethod GetImageVirtualPixelMethod( const Image *image );

IndexPacket * GetIndexes( const Image *image );

PixelPacket * GetOnePixel( const Image image, const long x, const long y );

PixelPacket * GetPixels( const Image image );

MagickBooleanType ModifyCache( Image *image, const unsigned long nexus );

Cache ReferenceCache( Cache cache_info );

PixelPacket * SetImagePixels( Image *image, const long x, const long y, const unsigned long columns, const unsigned long rows );

MagickBooleanType SetImageVirtualPixelMethod( const Image *image, const VirtualPixelMethod method );

MagickBooleanType SyncImagePixels( Image *image );

# FUNCTION DESCRIPTIONS

## AcquireImagePixels

> AcquireImagePixels() obtains a pixel region for read-only access. If the region is successfully accessed, a pointer to it is returned, otherwise NULL is returned. The returned pointer may point to a temporary working copy of the pixels or it may point to the original pixels in memory. Performance is maximized if the selected area is part of one row, or one or more full rows, since then there is opportunity to access the pixels in-place ( without a copy ) if the image is in RAM, or in a memory-mapped file. The returned pointer should *never *be deallocated by the user.

Pixels accessed via the returned pointer represent a simple array of type PixelPacket. If the image storage class is PsudeoClass, call `GetIndexes()` after invoking `GetImagePixels()` to obtain the colormap indexes (of type IndexPacket) corresponding to the region.

If you plan to modify the pixels, use `GetImagePixels()` instead.

> The format of the AcquireImagePixels() method is:

> const PixelPacket *AcquireImagePixels ( const Image *image, const long x, const long y, const unsigned long columns, const unsigned long rows, ExceptionInfo *exception );

A description of each parameter follows:

image:
  The image.

x,y,columns,rows:
  These values define the perimeter of a region of pixels.

exception:
  Return any errors or warnings in this structure.

## AcquireOnePixel

> AcquireOnePixel() returns a single pixel at the specified ( x, y ) location. The image background color is returned if an error occurs. If you plan to modify the pixel, use GetOnePixel ( ) instead.

> The format of the AcquireOnePixel() method is:

> PixelPacket AcquireOnePixel ( const Image image, const long x, const long y, ExceptionInfo exception );

A description of each parameter follows:

pixels:
  `AcquireOnePixel()` returns a pixel at the specified (x,y) location.

image:
  The image.

x,y:
  These values define the location of the pixel to return.

exception:
  Return any errors or warnings in this structure.

## DestroyCacheInfo

> DestroyCacheInfo() deallocates memory associated with the pixel cache.

> The format of the DestroyCacheInfo() method is:

> Cache DestroyCacheInfo ( Cache cache );

A description of each parameter follows:

cache:
  Specifies a pointer to a Cache structure.

## DestroyImagePixels

> DestroyImagePixels() deallocates memory associated with the pixel cache.

> The format of the DestroyImagePixels() method is:

> void DestroyImagePixels ( Image *image );

A description of each parameter follows:

image:
  The image.

## GetImagePixels

> GetImagePixels() obtains a pixel region for read/write access. If the region is successfully accessed, a pointer to it is returned, otherwise NULL is returned. The returned pointer may point to a temporary working copy of the pixels or it may point to the original pixels in memory. Performance is maximized if the selected area is part of one row, or one or more full rows, since then there is opportunity to access the pixels in-place ( without a copy ) if the image is in RAM, or in a memory-mapped file. The returned pointer should *never *be deallocated by the user.

> Pixels accessed via the returned pointer represent a simple array of type PixelPacket. If the image storage class is PsudeoClass, call GetIndexes() after invoking GetImagePixels ( ) to obtain the colormap indexes ( of type IndexPacket ) corresponding to the region. Once the PixelPacket ( and/or IndexPacket ) array has been updated, the changes must be saved back to the underlying image using SyncPixelCache ( ) or they may be lost.

> The format of the GetImagePixels() method is:

> PixelPacket *GetImagePixels ( Image *image, const long x, const long y, const unsigned long columns, const unsigned long rows );

A description of each parameter follows:

image:
  The image.

x,y,columns,rows:
  These values define the perimeter of a region of pixels.

## GetImageVirtualPixelMethod

> GetImageVirtualPixelMethod() gets the "virtual pixels" method for the image. A virtual pixel is any pixel access that is outside the boundaries of the image cache.

> The format of the GetImageVirtualPixelMethod() method is:

> VirtualPixelMethod GetImageVirtualPixelMethod ( const Image *image );

A description of each parameter follows:

image:
  The image.

## GetIndexes

> GetIndexes() returns the colormap indexes associated with the last call to SetImagePixels ( ) or GetImagePixels ( ) . NULL is returned if colormap indexes are not available.

> The format of the GetIndexes() method is:

> IndexPacket *GetIndexes ( const Image *image );

A description of each parameter follows:

indexes:
  `GetIndexes()` returns the indexes associated with the last call to `SetImagePixels()` or GetImagePixels().

image:
  The image.

## GetOnePixel

> GetOnePixel() returns a single pixel at the specified ( x, y ) location. The image background color is returned if an error occurs.

> The format of the GetOnePixel() method is:

> PixelPacket *GetOnePixel ( const Image image, const long x, const long y );

A description of each parameter follows:

image:
  The image.

x,y:
  These values define the location of the pixel to return.

## GetPixels

> GetPixels() returns the pixels associated with the last call to SetImagePixels ( ) or GetImagePixels ( ) .

> The format of the GetPixels() method is:

> PixelPacket *GetPixels ( const Image image );

A description of each parameter follows:

pixels:
  `GetPixels()` returns the pixels associated with the last call to `SetImagePixels()` or GetImagePixels().

image:
  The image.

## ModifyCache

> ModifyCache() ensures that there is only a single reference to the pixel cache to be modified, updating the provided cache pointer to point to a clone of the original pixel cache if necessary.

The format of the ModifyCache method is:

> MagickBooleanType ModifyCache ( Image *image, const unsigned long nexus );

A description of each parameter follows:

image:
  The image.

nexus:
  specifies which cache nexus to acquire.

## ReferenceCache

> ReferenceCache() increments the reference count associated with the pixel cache returning a pointer to the cache.

The format of the ReferenceCache method is:

> Cache ReferenceCache ( Cache cache_info );

A description of each parameter follows:

cache_info:
  The cache_info.

## SetImagePixels

> SetImagePixels() initializes a pixel region for write-only access. If the region is successfully intialized a pointer to it is returned, otherwise NULL is returned. The returned pointer may point to a temporary working buffer for the pixels or it may point to the final location of the pixels in memory. Performance is maximized if the selected area is part of one row, or one or more full rows, since then there is opportunity to access the pixels in-place ( without a copy ) if the image is in RAM, or in a memory-mapped file. The returned pointer should *never *be deallocated by the user.

Pixels accessed via the returned pointer represent a simple array of type PixelPacket. If the image storage class is PsudeoClass, call `GetIndexes()` after invoking `GetImagePixels()` to obtain the colormap indexes (of type IndexPacket) corresponding to the region. Once the PixelPacket (and/or IndexPacket) array has been updated, the changes must be saved back to the underlying image using `SyncPixelCache()` or they may be lost.

> The format of the SetImagePixels() method is:

> PixelPacket *SetImagePixels ( Image *image, const long x, const long y, const unsigned long columns, const unsigned long rows );

A description of each parameter follows:

pixels:
  SetImagePixels returns a pointer to the pixels if they are transferred, otherwise a NULL is returned.

image:
  The image.

x,y,columns,rows:
  These values define the perimeter of a region of pixels.

## SetImageVirtualPixelMethod

> SetImageVirtualPixelMethod() sets the "virtual pixels" method for the image. A virtual pixel is any pixel access that is outside the boundaries of the image cache.

> The format of the SetImageVirtualPixelMethod() method is:

> MagickBooleanType SetImageVirtualPixelMethod ( const Image *image, const VirtualPixelMethod method );

A description of each parameter follows:

image:
  The image.

method:
  choose from these access types:

          EdgeVirtualPixelMethod:  the edge pixels of the image extend
          infinitely.  Any pixel outside the image is assigned the same value as
          the pixel at the edge closest to it.
          TileVirtualPixelMethod:  the image extends periodically or tiled.  The
          pixels wrap around the edges of the image.
          MirrorVirtualPixelMethod:  mirror the image at the boundaries.
          ConstantVirtualPixelMethod:  every value outside the image is a
          constant as defines by the pixel parameter.
    =head2 SyncImagePixels

> SyncImagePixels() saves the image pixels to the in-memory or disk cache. The method returns MagickTrue if the pixel region is synced, otherwise MagickFalse.

> The format of the SyncImagePixels() method is:

> MagickBooleanType SyncImagePixels ( Image *image );

A description of each parameter follows:

image:
  The image.

"Image manipulation software that works like magick"