2D Interpolation (Linear and spline) of a greyscale image

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Graham Boag 2011-2-25

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https://ww2.mathworks.cn/matlabcentral/answers/2035-2d-interpolation-linear-and-spline-of-a-greyscale-image

评论： image-pro 2022-4-17

采纳的回答： Sean de Wolski

Hi Guys,

I have a grey scale image (shown below):

http://www.qfpost.com/download.do?get=f8295c24e09fe632b90a1d09ae5ac69a

Which I wish to interpolate to give 10 times the number of pixels - This is so I can find the edge of the beam when using a white-black intensity graph across the image as the edge is not exactly on a pixel - after carrying out a Canny edge detection.

The following code:

ZI = interp2(X,Y,Z,XI,YI,method)

seems to be the code I require where method will be 'linear' etc, however, I am not sure what the values X,Y,Z,XI and YI should be.

I guess that Z is my image, and the X and Y are co-ordinates of some kind but how would I determine then? I think it has something to do with meshgrids but I do not know very much about such techniques.

Any help would be much appreciated! Thanks, Graham

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Deepshikha Bhargava 2018-12-3

did you find the solution?

Image Analyst 2018-12-3

Yes. Scroll down the page and see the Answer with the green check mark, meaning he accepted that answer.

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采纳的回答

Sean de Wolski 2011-2-25

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https://ww2.mathworks.cn/matlabcentral/answers/2035-2d-interpolation-linear-and-spline-of-a-greyscale-image#answer_3178

在 MATLAB Online 中打开

Z is your image. You'll want to convert it to double for the interpolation and then back to uint8 or whatever other class after:

 I = your_image;
 class_of_I = class(I);
 [x y] = meshgrid(1:256);
 [xi yi] = meshgrid(1:0.1:256);
 class_of_I
 New_Image = cast(interp2(x,y,double(I),xi,yi,'linear'),class_of_I);

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Graham Boag 2011-3-1

It does show me the new_image but also it says:

Warning: Image is too big to fit on screen; displaying at 25%

> In imuitools\private\initSize at 73

In imshow at 262

Is there a way I can save the full image to avoid the warning?

Graham Boag 2011-3-1

I got it, sorry, nevermind!

imwrite(New_Image, 'new.tif')

seems to work! Thanks again for all your help with this problem Sean!

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Sean de Wolski 2011-2-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2035-2d-interpolation-linear-and-spline-of-a-greyscale-image#answer_3158

在 MATLAB Online 中打开

X,Y are the results of:

[X Y] = meshgrid(1:256)

Xi, Yi are the locations that you want an interpolated value at, for your example:

 [Xi Yi] = meshgrid(1:0.1:256);
 %SCd

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Graham Boag 2011-2-25

I seem to get the following error when I type my code:

ZI = interp2(X,Y,Z,Xi,Yi)

??? Error using ==> times

Integers can only be combined with integers of the same

class, or scalar doubles.

Error in ==> interp2>linear at 354

F = ( arg3(ndx).*(onemt) + arg3(ndx+1).*t ).*(1-s)

+ ...

Error in ==> interp2 at 220

zi = linear(ExtrapVal,x,y,z,xi,yi);

Graham Boag 2011-2-25

Sorry the above answer is when i typed a random value for Z. If I type:

Z = peaks(X,Y);

It seems to run for ages..then i type imshow(ZI) and I get a message saying the image is too big to fit on screen. Have I run the method correctly? Sorry If this is not so clear

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