Determining vector Xq and Yq for interp2 with scale

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Katarzyna Wieciorek
评论： Star Strider 2015-4-29
Hello,
I am studying how to make interpolation in image processing.
My error: Undefined function or variable 'scale'. Error in PL7ex3 (line 4) X1 = 1:1/scale:size(I0grey,2);
%PL7. Compare different methods for interpolation.
I0 = imread('glomeruli.tif'); %MxNx3
I0grey = im2double(rgb2gray(I0)); %grey, MxN
%interp2
X1 = 1:1/scale:size(I0grey,2);
Y1 = (1:1/scale:size(I0grey,1))';
X2 = 1:1/scale:size(I0grey,2);
Y2 = (1:1/scale:size(I0grey,1))';
I01 = interp2(I0grey, X1, Y1);
I02 = interp2(I0grey, X1, Y1, 'nearest');
I03 = interp2(I0grey, X1, Y1, 'cubic');
I04 = interp2(I0grey, X1, Y1, 'spline');
%Vq = interp2(___,method) specifies an optional, trailing input argument
%that you can pass with any of the previous syntaxes. The method argument
%can be any of the following strings that specify alternative interpolation
%methods: 'linear', 'nearest', 'cubic', or 'spline'. The default method is
%'linear'.
figure(1) % create new figure
subplot(2,3,1) % first subplot
imshow(I0)
title('Original')
subplot(2,3,2)
imshow(I0gray)
title('Original in greyscale')
subplot(2,3,3)
imshow(I01)
title('Linear interpolation')
subplot(2,3,4)
imshow(I02)
title('Interpolation 2: Nearest sample grid point.')
subplot(2,3,5)
imshow(I03)
title('Interpolation 3: Cubic convolution')
subplot(2,3,7)
imshow(I04)
title('Interpolation 4: Cubic spline')
figure(2) % create new figure
subplot(2,3,1) % first subplot
plot(I0(:,50))
title('Original')
subplot(2,3,2)
plot(I0gray(:,50))
title('Original in greyscale')
subplot(2,3,3)
plot(I01(:,50))
title('Linear interpolation')
subplot(2,3,4)
plot(I02(:,50))
title('Interpolation 2: Nearest sample grid point.')
subplot(2,3,5)
plot(I03(:,50))
title('Interpolation 3: Cubic convolution')
subplot(2,3,7)
plot(I04(:,50))
title('Interpolation 4: Cubic spline')
I rewrote this line from the example that prof. was showing us. Is there any misspelling? How can I correct it?
Thank you in advance.

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采纳的回答

Star Strider
Star Strider 2015-4-22
Ask your professor what ‘scale’ is supposed to be, and how you would assign it or calculate it.
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Katarzyna Wieciorek
Katarzyna Wieciorek 2015-4-29
I solved my problem. If there is anyone with similar it may be useful:
%y = linspace(x1,x2,n), separation 0.5 = (x2-x1)/(n-1)
[sy,sx] = size(I0grey);
nx = 2*sx-1;
ny = 2*sy-1;
X1 = linspace(1,sx,nx);
Y1 = (linspace(1,sy,ny))';

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