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    copied!<p>There are three main points of confusion:</p> <ol> <li>It's best not to use char* when the buffer the pointer is pointing to is not a null-terminated string as it's confusing. </li> <li>strlen() will only give you the length of a null-terminated string, it won't give you the size of an arbitrary buffer in memory. You need to get that information elsewhere.</li> <li>The buffer you pass to lzo1x_1_compress() actually needs to contain the data you want to compress and not an empty buffer full of zeros.</li> </ol> <p>Assuming you can get the size of your image from imageIn using something like imageIn->getFrameSizeBytes(), try this:</p> <pre><code> int r; lzo_bytep out; lzo_voidp wrkmem; lzo_uint out_len; lzo_uint new_len; /* * Step 1: initialize the LZO library */ if (lzo_init() != LZO_E_OK) { cout &lt;&lt; "internal error - lzo_init() failed !!!" &lt;&lt; endl; cout &lt;&lt; "(this usually indicates a compiler bug - try recompiling\nwithout optimizations, and enable '-DLZO_DEBUG' for diagnostics)" &lt;&lt; endl; //return 4; } // here I get the data I want to compress lzo_bytep imageData = (lzo_bytep) imageIn-&gt;getFrame(); size_t uncompressedImageSize = imageIn-&gt;getFrameSizeBytes(); /* * Step 2: allocate blocks and the work-memory */ out = (lzo_bytep) xmalloc((uncompressedImageSize + uncompressedImageSize / 16 + 64 + 3)); wrkmem = (lzo_voidp) xmalloc(LZO1X_1_MEM_COMPRESS); if (out == NULL || wrkmem == NULL) { cout &lt;&lt; "out of memory" &lt;&lt; endl; //return 3; } /* * Step 4: compress from 'imageData' to 'out' with LZO1X-1 */ r = lzo1x_1_compress(imageData,uncompressedImageSize,out,&amp;out_len,wrkmem); if (r != LZO_E_OK) { /* this should NEVER happen */ cout &lt;&lt; "internal error - compression failed: " &lt;&lt; r &lt;&lt; endl; //return 2; } /* check for an incompressible block */ if (out_len &gt;= uncompressedImageSize) { cout &lt;&lt; "This block contains incompressible data." &lt;&lt; endl; //return 0; } </code></pre> <p>Don't forget to free wrkmem. Even better, use C++ and std::vector for the working memory so it is freed automatically.</p>
 

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