dct matlab
时间: 2023-08-20 15:12:32 浏览: 54
DCT(离散余弦变换)是一种在图像处理中常用的变换方法,可以将图像从空域转换到频域。在MATLAB中,可以使用dct2函数对图像进行DCT变换。首先,需要打开MATLAB并在编辑器中编写以下代码:
```matlab
clear %清除工作区间
RGB=imread('G:\MATLAB\bm.bmp'); %加载图片
GRAY=rgb2gray(RGB); %彩色转灰度图
figure,imshow(GRAY); %显示灰度图
D=dct2(GRAY); %进行dct变换
figure,imshow(log(abs(D)),\[ \]); %显示变换过程
colormap(gray(4));
colorbar;
D(abs(D)<0.1)=0;
I=idct2(D)/255; %设置限值
figure,imshow(I) %显示变换后的图
```
这段代码首先加载一张彩色图片,并将其转换为灰度图。然后,对灰度图进行DCT变换,并显示变换过程。接下来,根据设定的阈值将DCT系数小于0.1的部分置零。最后,使用逆DCT变换将图像恢复,并显示变换后的图像。
另外,如果你想计算原始图像和压缩后图像所需的位数,可以使用以下代码:
```matlab
% Calculate how many bits should be used to represent the original images
% and store it in the variable B0
clear tempmatr1;
tempmatr1 = ceil(log2(orig_image+1));
clear sizevector1;
sizevector1 = size(orig_image);
\[rownum, colnum\] = size(sizevector1);
while colnum > 1
clear tempmatr2;
tempmatr2 = sum(tempmatr1);
clear tempmatr1;
tempmatr1 = tempmatr2;
colnum = colnum - 1;
end
B0 = sum(tempmatr1);
% Calculate how many bits should be used to represent the compressed images
% and store it in the variable B1
clear tempvec1;
tempvec1 = find(comp_image<0);
clear tempmatr1;
if sum(tempvec1) == 0
tempmatr1 = ceil(log2(comp_image+1));
else
tempmatr1 = ceil(log2(abs(comp_image)+1))+1;
end
clear sizevector1;
sizevector1 = size(comp_image);
\[rownum, colnum\] = size(sizevector1);
while colnum > 1
clear tempmatr2;
tempmatr2 = sum(tempmatr1);
clear tempmatr1;
tempmatr1 = tempmatr2;
colnum = colnum - 1;
end
B1 = sum(tempmatr1);
comp_ratio = B0/B1;
```
这段代码可以计算原始图像和压缩后图像所需的位数,并将结果存储在变量B0和B1中。最后,可以通过B0和B1的比值计算压缩比。
#### 引用[.reference_title]
- *1* [MATLAB中的DCT实现](https://blog.csdn.net/dyq1995/article/details/86149368)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insert_down1,239^v3^insert_chatgpt"}} ] [.reference_item]
- *2* *3* [【图像压缩】基于matlab DCT变换图像压缩【含Matlab源码 804期】](https://blog.csdn.net/TIQCmatlab/article/details/115972699)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insert_down1,239^v3^insert_chatgpt"}} ] [.reference_item]
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