Help with "for" loop

[SoSolid]

Hello,

I am wanting to create a for loop in Matlab which will allow me to cycle an image through various sizes. The code to do this is imresize(image, scaling factor)

I wrote my loop as follows but it does not work;

for n = 0.1:0.1:1
h = imresize(image1, n)
c = normxcorr2(image2,h)
end

I am wanting to scale image1 through various sizes, correlating it with a larger image each time in order to find the best match. However this is not happening, I know I have written the loop incorrectly but I cannot see where exactly.

 

[Amleto]

thats because you dont save the best case into c, you save the value from the last iteration in the loop.

are you sure that h > image2? that is a requirement as well.

 

[Helium_Junkie]

Just out of curiosity, how are the results output? Considering how quickly that for loop would be executed if it is resizing a displayed image you wouldn't even see the 10 smaller versions as it would seem to instantly move to the final iteration.

Also, C is unreferenced, so has no effect? Unless there is a visible effect from the normxcorr2 function...?

 

[SoSolid]

It should have been c = normxcorr2(h,image2). I think I need to do something like this:

for i = 0.1:0.1:1
h(i) = imresize(image1,i);
c(i) = normxcorr2(h,image2);
end

 

[Amleto]

for i = 0.1:0.1:1
h(i) = imresize(image1,i);
c(i) = normxcorr2(h(i),image2);
end

but you needn't save each h(i), and you only need to keep the 'best' c.

have you sorted it or need more help?

 

[SoSolid]

for i = 0.1:0.1:1
h(i) = imresize(image1,i);
c(i) = normxcorr2(h(i),image2);
end

but you needn't save each h(i), and you only need to keep the 'best' c.

have you sorted it or need more help?

Need more help.

 

[Amleto]

gimme some test data and expected results. I'll try and have a go tomorrow after work.

what error message, if any, do you get?

this:

c(i)= ...

wont work either since the rhs needs to return a 2-d matrix (I think), and that cant go into a single index, c(i).
However,

c(i,:,:) = ....

should be ok if that is the case.

 

[SoSolid]

When I use the original loop I posted, I got this error, Subscript indices must either be real positive integers or logicals.

 

[Amleto]

you dont have any subscript indices in your original post.

in

for i = 0.1:0.1:1
h(i) = imresize(image1,i);
c(i) = normxcorr2(h,image2);
end

I missed that you cant use i in c(i) since i = 0.1 0.2 0.3 etc. which would give you that error message.

 

[SoSolid]

you dont have any subscript indices in your original post.

in

for i = 0.1:0.1:1
h(i) = imresize(image1,i);
c(i) = normxcorr2(h,image2);
end

I missed that you cant use i in c(i) since i = 0.1 0.2 0.3 etc. which would give you that error message.

So how do I get around it?

 

[Inquisitor]

Use integers as subscripts, like the error message says

 

[Amleto]

j=1;
for i = 0.1:0.1:1
  h(j) = imresize(image1,i);
  c(j,:,:) = normxcorr2(h,image2);
  j=j+1;
end

 

[SoSolid]

j=1;
for i = 0.1:0.1:1
  h(j) = imresize(image1,i);
  c(j,:,:) = normxcorr2(h,image2);
  j=j+1;
end

That still won't work, I get: ??? Subscripted assignment dimension mismatch.

 

[Amleto]

you need to give more of your code. depends on the type of image you use.

sounds like you might be using colour images.

what is the size of normxcorr2(h,image2)?

x=normxcorr2(h,image2);
size(x);

 

[SoSolid]

you need to give more of your code. depends on the type of image you use.

sounds like you might be using colour images.

what is the size of normxcorr2(h,image2)?

x=normxcorr2(h,image2);
size(x);

I am using grayscale images.

 

[Amleto]

I cant help any more until you give more info, like I have asked for previously, like images you are using, and more of your code.