How to extend an image using convolution

2014 5 16
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更新时间：2014 5 16
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Hi I have this plot which I saved as an image. I need to extend it to a certain width. I think I can use convolution? I haven't done any image processing before. Absolutely new to this. Read about convolution so have an idea what it is. Can someone please guide me through this. How do I perform convolution for this?

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回答（1 个）

Image Analyst
Image Analyst 2014-5-16

0 个投票

Convolution will enlarge an image but it filters the image and you haven't said that you want to blur or sharpen the image. Why not try padarray() to just add some layers of zero value pixels around the outer edge of the image?

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Mahi Nazir
Mahi Nazir 2014-5-16
How will padding some layers of zero value pixels give the natural decay (not sure if I am using the right term) of the function over the specified width? If I say ok I want to blur my image but I need to extend it to say 0.9 cm with... how do I do that? Whats different in sharpening? because I want my profile extended to a width of say 0.9 cm
Mahi Nazir
Mahi Nazir 2014-5-16
by decay I mean like a sinc function
Image Analyst
Image Analyst 2014-5-16
You said "plot which I saved as an image" meaning that you made a plot , then you saved the plot (axes, blue line, tick labels, white space, etc.) as an image using something like saveas() or export_fig(). You didn't say anything about the blue line in the image which you plotted in that plot/chart/graph. That blue line is a 1-D signal, not an image so I did not expect that you would be talking about that. Is it THAT that you want to talk about rather than the "plot which I saved as an image"?
Mahi Nazir
Mahi Nazir 2014-5-16
Sorry for not being so clear... yes all I want is about the blue plot inside
Mahi Nazir
Mahi Nazir 2014-5-16
I am not sure if I even need this image ... I have a vector for that blue plot.. what do I do next to extend it sideways (decreasing) to a certain width?
Mahi Nazir
Mahi Nazir 2014-5-16
I don't need the axes and other markings... Can you please help
Image Analyst
Image Analyst 2014-5-16
OK, so you have a 1D array that is your signal. You can extend it by setting a later index. Let's say it's 15 long and you want it to be 30 long. You can do this:
vec(30) = 99; % Fill elements 16-29 with 0 and element 30 with 99.
Of course you can have the 99 be zero, but I just wanted to illustrate that all the "in between values" will be zero and the one you set will have the value you set.
Mahi Nazir
Mahi Nazir 2014-5-16
That's not what I want... I have a 1D array which is 41 long... I have to extend it... broaden it not lengthen it.... so the width of the array will change and it will have to become a matrix....
Image Analyst
Image Analyst 2014-5-16
To make the line broader, set the 'LineWidth' option:
plot(x,y, 'LineWidth', 5);
Mahi Nazir
Mahi Nazir 2014-5-16
I need something like a surface plot as my result... something like the image attached(only the central part of if obviously)... not just increased width
Image Analyst
Image Analyst 2014-5-16
Try the surf() function.
Mahi Nazir
Mahi Nazir 2014-5-16
For surf we need to have a matrix, I have a vector... that's why I was trying to get additional values from convolution? Any idea how convolution can be done here?

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