应用CXimage类库做的一个图像处理的实例程序，看看CXimage类库有多强大

<!--#include virtual="header.shtml" --> <!--#include virtual="/global/getCss.inc" --> <CENTER><H3><FONT COLOR="#AOAO99"> [CxImageMNG - A class to read MNG, JNG and PNG images] </FONT></H3></CENTER><HR> <!-- Author and contact details --> This article was contributed by <A HREF="mailto:[ing.davide.pizzolato@libero.it]">Davide Pizzolato</A>. <!-- For which environment is this code specific??? --> <p><img src="cximagemng.gif" width="322" height="231"></p> <p><u>Environment:</u> VC6 <h3>Introduction</h3> <p><code>CxImageMNG</code> is the module of <code><a href="http://www.aoi.it/code.htm">CxImage</a></code> used to play MNG animations. It uses the CxImage members, but to play the animation are necessary additional variables and functions. I decided to keep separated the MNG stuff from the &quot;static&quot; formats, to limit the growth of the base class due to the new features. <p>As with the other modules, CxImageMNG is mainly an interface for the LibMNG functions, it takes care of the I/O operations and of the specific requirements of the library. CxImageMNG can read also PNG and JNG images. <p>This class requires some extra libraries to work: <b>LibMNG</b>, you can find <a href="http://www.libpng.org">here</a> the latest version; <b>JPEG and ZLIB libraries</b>, used by LibMNG to endode/decode files. All these libraries are included in the source code. <h3>Structures &amp; callbacks</h3> <p>&quot;Libmng makes extensive use of callback functions. This is meant to keep the library as platform-independant and flexible as possible.&quot;, in CxImageMNG these are declared as:</p> <pre>mng_setcb_errorproc (mng_handle, mymngerror); mng_setcb_openstream (mng_handle, mymngopenstream); mng_setcb_closestream (mng_handle, mymngclosestream); mng_setcb_readdata (mng_handle, mymngreadstream); mng_setcb_processheader(mng_handle, mymngprocessheader); mng_setcb_getcanvasline(mng_handle, mymnggetcanvasline); mng_setcb_refresh (mng_handle, mymngrefresh); mng_setcb_gettickcount (mng_handle, mymnggetticks); mng_setcb_settimer (mng_handle, mymngsettimer); mng_setcb_refresh (mng_handle, mymngrefresh);</pre> Some of these are empty (<code>mymngopenstream</code>), or obvious (<code>mymngreadstream</code>), the most useful for the final applications are <code>mymngprocessheader</code>, where we get the first informations about the image, and <code>mymngsettimer</code>, where get the essential value for the timer. <p>Another important parameter is <code>pUserdata</code>, where the application can store its parameters, in CxImageMNG this is a pointer to the <code>mnginfo</code> variable.</p> <pre>typedef struct { FILE *file; // file handle BYTE *image; // image pixels HANDLE thread; // timer mng_uint32 delay; // timer duration mng_uint32 width; // image attributes mng_uint32 height; mng_uint32 effwdt; mng_int16 bpp; mng_bool animation; // true if it's an animation mng_bool animation_enabled; // enable the timer float speed; // speed factor } mngstuff;</pre> <p>In the callbacks, these informations are available at all times through the <code>mng_get_userdata</code> function. </p> <h3>How to play animations</h3> <p>First we must load the file:</p> <pre>image = new CxImageMNG(); image-&gt;ReadFile(filename);</pre> <p>then, if it's an animation, we must create a thread to play it:</p> <pre>if (image->mnginfo.animation) { image->mnginfo.animation_enabled=1; DWORD dwID; image->mnginfo.thread = CreateThread(NULL,0,RunMNGThread,this,0,&dwID); }</pre> <p>In the end we must handle the execution of the thread :</p> <pre>unsigned long _stdcall RunMNGThread(void *lpParam){ Sleep((DWORD)(image->mnginfo.delay / image->mnginfo.speed)); while (image->mnginfo.animation_enabled && image->Resume()){ SendMessage(hWnd, WM_USER_NEWFRAME,0,0); Sleep((DWORD)(image->mnginfo.delay / image->mnginfo.speed)); } image->mnginfo.thread=0; return 0; }</pre> <p>The <code>WM_USER_NEWFRAME</code> message tells to the main application that a new frame is ready to be shown. The <code>Resume()</code> function is used to obtain the next frame.<br> To stop the animation simply set <code>image-&gt;mnginfo.animation_enabled = 0.<br> </code>The thread is automatically closed in the CxImageMNG destructor.</p> <p>Finally you can display the image: <code>image-&gt;Draw(pDC-&gt;GetSafeHdc());</code></p> <h3>Credits.</h3> <ul> <li>LIBMNG Copyright (c) 2000,2001 Gerard Juyn (gerard@libmng.com).<br> <li>Original mng.cpp code created by Nikolaus Brennig, November 14th, 2000. (virtualnik@nol.at).<br> <li>Special thanks to Frank Haug (f.haug@jdm.de) for suggestions and code.</li> </ul> <p>More specific credits and disclaimers are in every header file of each library.<br> </p> <h3>Downloads</h3> <!-- demo and source files --> <A HREF="cximagemng_demo.zip"> Download demo - 165 Kb</A><BR> <A HREF="cximagemng_src.zip"> Download full source code - 752 Kb</A> <h3>History</h3> Date Posted: 11/18/2001<BR> <!--#include virtual="footer.shtml" -->