downsampling image

hello

i have an original image of size 288x360 ..i need to perform the decomposition of this image into constituent polyphase components of 144x180 frames..

please suggest some way in matlab to do it..

presently i am tring it with gtdecomp command without any success..

Answer 1

[Wayne King]

Hi, You can use dyaddown() from the Wavelet Toolbox.

    x = randn(8,8);
    % this gives you 1st row, 1st column, 3rd row, 3rd colum, etc
    y = dyaddown(x,'m',1);
    % now this gives you 2nd row, 2nd column, etc
    y = dyaddown(x,'m',0);

Or you can use downsample() from the Signal Processing Toolbox. This gives you one polyphase matrix.

     Y = downsample(x,2,0);
     Y = (downsample(Y',2,0))';

This gives you the other:

       Y1 = downsample(x,2,1);
       Y1 = (downsample(Y1',2,1))';

Hope that helps,

Wayne

[Max]

yes it worked ..and now i have the downsampled images too. thank you so much Wayne

[juveria fatima]

downsampling will loose the image data

what is the efficient way to compress image with out data loss

Answer 2

[SK Ahsan]

How Many Different Techniques Are Applied To Downsample An Image? Can Any One Elaborate It?