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<title>ImageMagick: MagickCore, C API for ImageMagick: Get or Set Image Pixels</title>
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<p class="navigation-index">[ <a href="#AcquirePixelCacheNexus">AcquirePixelCacheNexus</a> | <a href="#GetAuthenticIndexQueue">GetAuthenticIndexQueue</a> | <a href="#GetAuthenticPixelQueue">GetAuthenticPixelQueue</a> | <a href="#GetAuthenticPixels">GetAuthenticPixels</a> | <a href="#GetOneAuthenticPixel">GetOneAuthenticPixel</a> | <a href="#GetOneVirtualMagickPixel">GetOneVirtualMagickPixel</a> | <a href="#GetOneVirtualMethodPixel">GetOneVirtualMethodPixel</a> | <a href="#GetOneVirtualPixel">GetOneVirtualPixel</a> | <a href="#GetVirtualIndexQueue">GetVirtualIndexQueue</a> | <a href="#GetVirtualPixelQueue">GetVirtualPixelQueue</a> | <a href="#GetVirtualPixels">GetVirtualPixels</a> | <a href="#QueueAuthenticPixels">QueueAuthenticPixels</a> | <a href="#SetPixelCacheVirtualMethod">SetPixelCacheVirtualMethod</a> | <a href="#SyncAuthenticPixels">SyncAuthenticPixels</a> ]</p>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="AcquirePixelCacheNexus">AcquirePixelCacheNexus</a></h2>
</div>
<p>AcquirePixelCacheNexus() allocates the NexusInfo structure.</p></ol>
<p>The format of the AcquirePixelCacheNexus method is:</p>
<pre class="code">
NexusInfo **AcquirePixelCacheNexus(const unsigned long number_threads)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>number_threads</h5>
<ol><p>the number of nexus threads.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetAuthenticIndexQueue">GetAuthenticIndexQueue</a></h2>
</div>
<p>GetAuthenticIndexQueue() returns the authentic black channel or the colormap indexes associated with the last call to QueueAuthenticPixels() or GetVirtualPixels(). NULL is returned if the black channel or colormap indexes are not available.</p></ol>
<p>The format of the GetAuthenticIndexQueue() method is:</p>
<pre class="code">
IndexPacket *GetAuthenticIndexQueue(const Image *image)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetAuthenticPixelQueue">GetAuthenticPixelQueue</a></h2>
</div>
<p>GetAuthenticPixelQueue() returns the authentic pixels associated with the last call to QueueAuthenticPixels() or GetAuthenticPixels().</p></ol>
<p>The format of the GetAuthenticPixelQueue() method is:</p>
<pre class="code">
PixelPacket *GetAuthenticPixelQueue(const Image image)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetAuthenticPixels">GetAuthenticPixels</a></h2>
</div>
<p>GetAuthenticPixels() 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.</p></ol>
<p>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 region 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.</p></ol>
<p>Pixels accessed via the returned pointer represent a simple array of type PixelPacket. If the image type is CMYK or if the storage class is PseduoClass, call GetAuthenticIndexQueue() after invoking GetAuthenticPixels() to obtain the black color component or 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 SyncAuthenticPixels() or they may be lost.</p></ol>
<p>The format of the GetAuthenticPixels() method is:</p>
<pre class="code">
PixelPacket *GetAuthenticPixels(Image *image,const long x,const long y,
const unsigned long columns,const unsigned long rows,
ExceptionInfo *exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>x,y,columns,rows</h5>
<ol><p>These values define the perimeter of a region of pixels.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetOneAuthenticPixel">GetOneAuthenticPixel</a></h2>
</div>
<p>GetOneAuthenticPixel() returns a single pixel at the specified (x,y) location. The image background color is returned if an error occurs.</p></ol>
<p>The format of the GetOneAuthenticPixel() method is:</p>
<pre class="code">
MagickBooleanType GetOneAuthenticPixel(const Image image,const long x,
const long y,PixelPacket *pixel,ExceptionInfo *exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>x,y</h5>
<ol><p>These values define the location of the pixel to return.</p></ol>
<h5>pixel</h5>
<ol><p>return a pixel at the specified (x,y) location.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetOneVirtualMagickPixel">GetOneVirtualMagickPixel</a></h2>
</div>
<p>GetOneVirtualMagickPixel() 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 GetOneAuthenticPixel() instead.</p></ol>
<p>The format of the GetOneVirtualMagickPixel() method is:</p>
<pre class="code">
MagickBooleanType GetOneVirtualMagickPixel(const Image image,
const long x,const long y,MagickPixelPacket *pixel,
ExceptionInfo exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>x,y</h5>
<ol><p>these values define the location of the pixel to return.</p></ol>
<h5>pixel</h5>
<ol><p>return a pixel at the specified (x,y) location.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetOneVirtualMethodPixel">GetOneVirtualMethodPixel</a></h2>
</div>
<p>GetOneVirtualMethodPixel() returns a single pixel at the specified (x,y) location as defined by specified pixel method. The image background color is returned if an error occurs. If you plan to modify the pixel, use GetOneAuthenticPixel() instead.</p></ol>
<p>The format of the GetOneVirtualMethodPixel() method is:</p>
<pre class="code">
MagickBooleanType GetOneVirtualMethodPixel(const Image image,
const VirtualPixelMethod virtual_pixel_method,const long x,
const long y,Pixelpacket *pixel,ExceptionInfo exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>virtual_pixel_method</h5>
<ol><p>the virtual pixel method.</p></ol>
<h5>x,y</h5>
<ol><p>These values define the location of the pixel to return.</p></ol>
<h5>pixel</h5>
<ol><p>return a pixel at the specified (x,y) location.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetOneVirtualPixel">GetOneVirtualPixel</a></h2>
</div>
<p>GetOneVirtualPixel() returns a single virtual 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 GetOneAuthenticPixel() instead.</p></ol>
<p>The format of the GetOneVirtualPixel() method is:</p>
<pre class="code">
MagickBooleanType GetOneVirtualPixel(const Image image,const long x,
const long y,PixelPacket *pixel,ExceptionInfo exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>x,y</h5>
<ol><p>These values define the location of the pixel to return.</p></ol>
<h5>pixel</h5>
<ol><p>return a pixel at the specified (x,y) location.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetVirtualIndexQueue">GetVirtualIndexQueue</a></h2>
</div>
<p>GetVirtualIndexQueue() returns the virtual black channel or the colormap indexes associated with the last call to QueueAuthenticPixels() or GetVirtualPixels(). NULL is returned if the black channel or colormap indexes are not available.</p></ol>
<p>The format of the GetVirtualIndexQueue() method is:</p>
<pre class="code">
const IndexPacket *GetVirtualIndexQueue(const Image *image)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetVirtualPixelQueue">GetVirtualPixelQueue</a></h2>
</div>
<p>GetVirtualPixelQueue() returns the virtual pixels associated with the last call to QueueAuthenticPixels() or GetVirtualPixels().</p></ol>
<p>The format of the GetVirtualPixelQueue() method is:</p>
<pre class="code">
const PixelPacket *GetVirtualPixelQueue(const Image image)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="GetVirtualPixels">GetVirtualPixels</a></h2>
</div>
<p>GetVirtualPixels() returns an immutable pixel region. 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 region is part of one row, or one or more full rows, since 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.</p></ol>
<p>Pixels accessed via the returned pointer represent a simple array of type PixelPacket. If the image type is CMYK or the storage class is PseudoClass, call GetAuthenticIndexQueue() after invoking GetAuthenticPixels() to access the black color component or to obtain the colormap indexes (of type IndexPacket) corresponding to the region.</p></ol>
<p>If you plan to modify the pixels, use GetAuthenticPixels() instead.</p></ol>
<p>Note, the GetVirtualPixels() and GetAuthenticPixels() methods are not thread- safe. In a threaded environment, use GetCacheViewVirtualPixels() or GetCacheViewAuthenticPixels() instead.</p></ol>
<p>The format of the GetVirtualPixels() method is:</p>
<pre class="code">
const PixelPacket *GetVirtualPixels(const Image *image,const long x,
const long y,const unsigned long columns,const unsigned long rows,
ExceptionInfo *exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>x,y,columns,rows</h5>
<ol><p>These values define the perimeter of a region of pixels.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="QueueAuthenticPixels">QueueAuthenticPixels</a></h2>
</div>
<p>QueueAuthenticPixels() queues a mutable pixel region. 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.</p></ol>
<p>Write-only access means that any existing pixel values corresponding to the region are ignored. This is useful if 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 QueueAuthenticPixels() any way it pleases. QueueAuthenticPixels() does not initialize the pixel array values. Initializing pixel array values is the application's responsibility.</p></ol>
<p>Performance is maximized if the selected region 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.</p></ol>
<p>Pixels accessed via the returned pointer represent a simple array of type PixelPacket. If the image type is CMYK or the storage class is PseudoClass, call GetAuthenticIndexQueue() after invoking GetAuthenticPixels() to obtain the black color component or 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 SyncAuthenticPixels() or they may be lost.</p></ol>
<p>The format of the QueueAuthenticPixels() method is:</p>
<pre class="code">
PixelPacket *QueueAuthenticPixels(Image *image,const long x,const long y,
const unsigned long columns,const unsigned long rows,
ExceptionInfo *exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>x,y,columns,rows</h5>
<ol><p>These values define the perimeter of a region of pixels.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="SetPixelCacheVirtualMethod">SetPixelCacheVirtualMethod</a></h2>
</div>
<p>SetPixelCacheVirtualMethod() sets the "virtual pixels" method for the pixel cache and returns the previous setting. A virtual pixel is any pixel access that is outside the boundaries of the image cache.</p></ol>
<p>The format of the SetPixelCacheVirtualMethod() method is:</p>
<pre class="code">
VirtualPixelMethod SetPixelCacheVirtualMethod(const Image *image,
const VirtualPixelMethod virtual_pixel_method)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>virtual_pixel_method</h5>
<ol><p>choose the type of virtual pixel.</p></ol>
<div style="margin: auto;">
<h2><a href="http://www.imagemagick.org/api/MagickCore/cache
_8c.html" target="source" name="SyncAuthenticPixels">SyncAuthenticPixels</a></h2>
</div>
<p>SyncAuthenticPixels() saves the image pixels to the in-memory or disk cache. The method returns MagickTrue if the pixel region is flushed, otherwise MagickFalse.</p></ol>
<p>The format of the SyncAuthenticPixels() method is:</p>
<pre class="code">
MagickBooleanType SyncAuthenticPixels(Image *image,
ExceptionInfo *exception)
</pre>
<p>A description of each parameter follows:</p></ol>
<h5>image</h5>
<ol><p>the image.</p></ol>
<h5>exception</h5>
<ol><p>return any errors or warnings in this structure.</p></ol>
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