Zoom Image Matlab?

Hi,

please want to zoom my image; How can i do please?

I done this code:

load navatalungo_H.asc
NP1 = 1151;
xx=linspace(0,0.02*(NP1-1),NP1);
imagesc(xx,t,navatalungo_H')

Answer 1

[Walter Roberson]

You can generally turn zoom on or off or set a zoom factor using zoom()

However, if you want to zoom to a particular section then the easiest way is to set the axes xlim and ylim . When you do this you should take into account that the xx and t coordinates are the coordinates of the centers of pixels, so you would want to nudge the limits a little to the left or right to include whole pixels.

Note: when you pass x and y values to image() or imagesc() or imshow(), then only the first and last values are paid attention to. If you need a non-linear presentation of an image you need to handle it a different way, such as using pcolor(), or texture mapping your image onto a surface or patch.

[denis bertin]

my image look like this, I just want to zoom the header.

[Walter Roberson]

After displaying the image, experiment with

YL = get(gca, 'ylim')
Ylim_at_top = [YL(2) - (YL(2)-YL(1))/6, YL(2)]
set(gca, 'YLim', Ylim_at_top)
pause
Ylim_at_bottom = [YL(1), YL(1) + (YL(2)-YL(1))/6];
set(gca, 'YLim', Ylim_at_bottom)
pause

and see if one of the two does what you want

[denis bertin]

Many Thank, it is exactly what i need.

[Walter Roberson]

Which one turned out to be the one you wanted?

[denis bertin]

The second. Ylim_at_bottom = [YL(1), YL(1) + (YL(2)-YL(1))/6]; set(gca, 'YLim', Ylim_at_bottom)

But i want to have the '/6' value dynamicly... Why have you divide by 6 please? not another number may be...

[Walter Roberson]

I did a visual examination and saw that the interesting information appeared to be between 0 and 0.2. When I looked at the tick marks and the width of the borders, it appears to me that the tick marks are about 1/12 of the height of the image (including borders). One tick plus keeping the border is about 1/12+1/12 = 1/6 of the height.

For anything dynamic you would need to have some way of calculating what part of the image was "interesting" to zoom into.

[denis bertin]

Thank you... Is it possible having 'grey' background color please?

[Walter Roberson]

I am not sure what you are asking about grey background. You can

set(gca, 'Color', [.1 .1 .1])

to get 1/10th intensity as the background. This will be visible only in the parts of the axes where nothing is drawn, but if you are zooming in using ylim then everything is going to be drawn on (unless you set the data aspect ratio somehow, such as "axis equal")

[denis bertin]

Hi, If you look the picture, background color was blu, i want it grey color.

After display image, i put this:

YL = get(gca, 'ylim') Ylim_at_bottom = [YL(1), YL(1) + (YL(2)-YL(1))/2.5];

set(gca, 'YLim', Ylim_at_bottom) set(gca, 'Color', [.1 .1 .1])

but i always have blu background color(see attach).

[Walter Roberson]

If you look at Cattur1.PNG that you posted first, the background color is white and the content of the image happens to be mostly blue. I think the blue is your image, not background.

[denis bertin]

Yes! it's true. Sorry, i would want grey image.

Thank you...

Answer 2

[Image Analyst]

See attached zoom demo, given to me by the Mathworks.

[Stephen Devlin]

Thank you Image Analyst, this is brilliant!

[Bang bang]

How can I contact you Image Analyst I have a lot of question for you

[Walter Roberson]

You can create Questions in MATLAB Answers.

Image Analyst does not accept private correspondence.