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<TITLE>signature - Methods to Compute a Digital Signature for an Image</TITLE>
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	<LI><A HREF="#NAME">NAME</A></LI>
	<LI><A HREF="#SYNOPSIS">SYNOPSIS</A></LI>
	<LI><A HREF="#FUNCTION_DESCRIPTIONS">FUNCTION DESCRIPTIONS</A></LI>
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		<LI><A HREF="#SignatureImage">SignatureImage</A></LI>
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<H1><A NAME="NAME">NAME</A></H1>
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signature - Methods to Compute a Digital Signature for an Image

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<H1><A NAME="SYNOPSIS">SYNOPSIS</A></H1>
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void  <STRONG>SignatureImage</STRONG>( Image <CODE>*image</CODE> );

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<H1><A NAME="FUNCTION_DESCRIPTIONS">FUNCTION DESCRIPTIONS</A></H1>
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<H2><A NAME="SignatureImage">SignatureImage</A></H2>
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Method SignatureImage computes a digital signature from an image. This signature uniquely identifies the image and is convenient for determining if the colormap of a sequence of images is identical when animating. The digital signature is from 
<FONT SIZE=-1>RSA</FONT> Data Security 
<FONT SIZE=-1>MD5</FONT> Digest Algorithm described in Internet draft 
<FONT SIZE=-1>[MD5],</FONT> July 1992, computed on the pixels after expanding them to 64-bit 
<FONT SIZE=-1>RGBA</FONT> representation, with the two bytes of each 16-bit sample ordered most significant byte first. The signature is in 
<FONT SIZE=-1>RGBA</FONT> or 
<FONT SIZE=-1>CMYK</FONT> order depending on the colorspace of the image. If the image does not have any alpha information, an opaque value (65535) is used.


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The format of the SignatureImage method is:

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<blockquote>void SignatureImage ( <A HREF="types/Image.html">Image</A> *image ); </blockquote>

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<FONT SIZE=-1>A</FONT> description of each parameter follows:

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<p><dt><STRONG><A NAME="item_o">image:</A></STRONG><DD>
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The address of a structure of type Image.

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