
<p class="wp-block-paragraph">è¿æåå äº&#8221;æ¸ä½å §å®¹èæ©å¨å¸ç¿&#8221;課ç¨ï¼å¨ééå°å¸ç¿å°çç¥èååçè¨ï¼è¥æé¯èª¤ä¹ç ©è«ä¸åææã</p>



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<p class="wp-block-paragraph">é¦å å°ååè³æåå²æ128*128çå°æ¹å¡é²è¡DCTè½æï¼</p>



<pre class="wp-block-code"><code>Image_DCT = blockproc(ImageInput, &#91;128 128], @(block) dct2(block.data));
Image_DCT(abs(Image_DCT) <; 10) = 0;
imshow(Image_DCT);</code></pre>



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<figure class="wp-block-image size-large"><img src="https://kerker.website/wp-content/uploads/2023/02/DCTéåjpg-1024x576.jpg" alt="" class="wp-image-1342"/></figure>



<p class="wp-block-paragraph">æ¯ä¸å128*128çç©é£å·¦ä¸è§é½éæå¯éçè¨èï¼ä½å³ä¸è§çé«é »è¨èå çµå°å¼å°æ¼10被è¨çº0äºã</p>



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<ol class="wp-block-list">
<li>DCTè½æå¾åæ大çNåå¼å ¶é¤æ¸é¶(é裡N帶100)ï¼</li>
</ol>



<pre class="wp-block-code"><code>Image_Input = imread('Baboon_Gray.tiff');
Image_DCT = blockproc(Image_Input, &#91;128 128], @(block) DCT_Top_N(block.data,100));
imshow(Image_DCT);

function data_dct_out = DCT_Top_N(data, N)
 data_dct_out = dct2(data);
 TopN_value = abs(reshape(data_dct_out,&#91;1,128*128]));
 TopN_value = min(maxk(TopN_value,N));
 data_dct_out(abs(data_dct_out) <; TopN_value) = 0;
 data_dct_out = idct2(data_dct_out);
 data_dct_out = rescale(data_dct_out);
end</code></pre>



<p class="wp-block-paragraph">2. <em>DCTè½æå¾ä¿çå·¦ä¸N</em>Nçå¼å ¶é¤æ¸é¶(é裡N帶50)ï¼</p>



<pre class="wp-block-code"><code>Image_DCT = blockproc(Image_Input, &#91;128 128], @(block) DCT_Top_Right(block.data,50));
imshow(Image_DCT);

function data_dct_out = DCT_Top_Right(data, N)
 data_dct = dct2(data);
 data_dct_out = data_dct*0;
 for i = 1:N
 for j = 1:N
 data_dct_out (i,j) = data_dct(i,j);
 end
 end
 data_dct_out = idct2(data_dct_out);
 data_dct_out = rescale(data_dct_out)
end</code></pre>



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