MATLAB: Error while compressing the image using dct2()

dct2error

Hi!
I am trying to compress image using DCT :
close all;
x=imread('image.jpeg');
figure,imshow(x);
F=dct2(x);
figure,imshow(F*0.01);
ff=idct2(F);
figure,imshow(ff/255);
[r,c]=size(x);
DF=zeros(r,c);
DFF=DF;
IDF=DF;
IDFF=DF;
depth=4;
N=8;
for i=1:N:r
  for j=1:N:c
    f=original(i:i+N-1,j:j+N-1);
    df=dct2(f);
    DF(i:i+N-1,j:j+N-1)=df;
    dff=idct2(df);
    DFF(i:i+N-1,j:j+N-1)=dff;
    
    
    df(:,N:-1:depth+1)=0;
    df(N:-1:depth+1,:)=0;
    IDF(i:i+N-1,j:j+N-1)=df;
    dff=idct2(df);
    IDFF(i:i+N-1,j:j+N-1)=dff;
   end
end
figure,imshow(DF/255);
figure,imshow(DFF);
A=DFF/255;
figure,imshow(A);
imwrite(A,'img.jpeg');
B=IDFF/255;
imwrite(B,'img_comp.jpeg');
figure,imshow(B);
Got this code from Online sources.
I am getting the following errors:
Matrix dimensions must agree.
Error in dct (line 76)
  b = W .* fft(y);
Error in dct2 (line 50)
    b = dct(dct(arg1).').';
Error in image_compression2 (line 4)
F=dct2(x);
Please help me resolve this Issue. Thanking you in Anticipation.

Best Answer

Hi Anuja,
This error can be solved by perfoming the RGB to gray conversion using rgb2gray function. To know the usage of dct2 with a example, look this page.
Hope this helps.
Regards,
Sriram
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