reducing resolution of an image
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I have an image having resolution of 256x256,i want to reduce the resolution of image to 128x128,64x64,without using imresize conmmand please help
回答（4 个）
Geoff
2012-5-9
2 个投票
Think about it...
If you half the width and height, that means each group of 2x2 pixels becomes one pixel. You average the pixel intensities for each block and set that as your new pixel.
Well, you don't have to average them. You could select one or do any number of statistics on the chunk. But you should start simple.
The rest is just loops and matrix indexing. I'm sure you can cope with that.
Jessica Lam
2012-5-9
you may try the following code. for resolution of 470 X 274
set(gcf,'PaperUnits','inches','PaperPosition',[0 0 4.7 2.74])
print('-dpng', 'filename.png', '-r100')
1 个评论
Walter Roberson
2012-5-9
That would seem to be increasing the resolution, rather than decreasing the resolution.
Jessica Lam
2012-5-9
0 个投票
just change the vector of PaperPosition from [ 0 0 4.7 2.74 ] to something you want
for example [0 0 1.28 1.28] for 128x128 or [0 0 0.64 0.64] for 64X64
1 个评论
Walter Roberson
2012-5-9
Seems like an expensive way of reducing the resolution...
Walter Roberson
2012-5-9
t = fft2(YourImage);
t(:,end/2+1:end) = [];
t(end/2+1:end,:) = [];
SmallerImage = ifft2(t);
or
t = reshape(YourImage, 2, size(YourImage,1)/2, 2, size(YourImage,2)/2, 2);
SmallerImage = cast(permute(mean(permute(mean(t,3),[1 2 4 3]),1),[1 2 3],[2 3 1]),class(YourImage));
3 个评论
kash
2012-5-9
Walter Roberson
2012-5-9
For the first one, you might need to use
SmallerImage = cast(ifft2(t), class(YourImage));
For the second one it looks like I had an additional 2:
t = reshape(YourImage, 2, size(YourImage,1)/2, 2, size(YourImage,2)/2);
kash
2012-5-9
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