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[ AcquireImagePixels | AcquireOnePixel | DestroyCacheInfo | DestroyImagePixels | GetImagePixels | GetImageVirtualPixelMethod | GetIndexes | GetOnePixel | GetPixels | ModifyCache | ReferenceCache | SetImagePixels | SetImageVirtualPixelMethod | SyncImagePixels ]

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() 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() 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

The pixel cache.

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() obtains a pixel region for read/write access. If the region is successfully accessed, a pointer to a PixelPacket array representing the region 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() 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() 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() 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() 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() 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() 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 pixel cache.

SetImagePixels() initializes a pixel region for write-only access. If the region is successfully intialized a pointer to a PixelPacket array representing the region 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.

Write-only access means that any existing pixel values corresponding to the region are ignored. This is useful while the initial image is being created from scratch, or if the existing pixel values are to be completely replaced without need to refer to their pre-existing values. The application is free to read and write the pixel buffer returned by SetImagePixels() any way it pleases. SetImagePixels() does not initialize the pixel array values. Initializing pixel array values is the application's responsibility.

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() 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.

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.