A beginners question to clarify something I am trying to do it MATLAB regarding an image

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Sam
Sam 2011-8-3
I am trying to learn how to use MATLAB so therefore am a complete beginner, I am sorry if this question is very basic or I do not use the correct terms/explain myself properly as I have no programming experience and I am finding it quite difficult to understand the help guide and textbook I have.
So I have created three variables for the colour bands by typing
Image_red=Image(:,:,1); Image_green=Image(:,:,2); Image_blue=Image(:,:,3);
and I can display one (eg red) by typing
figure, imagesc(Image_red), colormap(‘gray’)
The textbook I am working through then starts with the following instructions on using a variable to control the band selection.
Type >>band=1;
Then type >>Image_new=Image(:,:,band);
We will still get the red band in the new image. If we set band=2 then we would get the green band..
Write a new function called ‘draw1band.m’ which uses two input variables: an image name and another variable called ‘band’ to draw a grayscale image of either of the 3 bands. Once written, you should be able to type:
>>draw1band(‘srgmatlab’, 3)
And get a figure of the blue band.
I can't for the life of me figure out how to do this! Could anyone offer any help please? Thank you in advance. Sam
  1 个评论
Jan
Jan 2011-8-3
Please post what you have done so far and ask a specific question.
Reading the Getting Started sections of the documentation will help to learn the basics.

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采纳的回答

Florin Neacsu
Florin Neacsu 2011-8-3
Hi,
Have a look at "function". type
doc function
In this case you need something like:
function [] = draw1band(inputImage,band)
%maybe sanity checks for band and inputImage
oneCh=inputImage(:,:,band);
figure
imagesc(oneCh);
colormap gray;
end
You need to save this as an .m file. You can do this in many ways. Maybe try :
edit draw1band
Feel free to have a look at the FAQ page http://matlab.wikia.com/wiki/FAQ
Regards, Florin

更多回答（2 个）

Paulo Silva
Paulo Silva 2011-8-3
Simple code to show one image and each rgb components on different axes
name='ngc6543a.jpg';
subplot(411)
rgb = imread(name);
imagesc(rgb); title(['RGB image ' name])
for band=1:3
subplot(4,1,band+1)
im=rgb(:,:,band);
imagesc(im); title(['Image using band=' num2str(band)])
colormap('gray')
end
Now one possible function
function draw1band(Iname,band)
%example use from MATLAB documentation
%Iname='ngc6543a.jpg';
%band=1;
subplot(211)
rgb = imread(Iname);
imagesc(rgb); title(['RGB image ' Iname])
subplot(212)
im=rgb(:,:,band);
imagesc(im); title(['Image using band=' num2str(band)])
colormap('gray')
end
Sam
Sam 2011-8-5
Thanks, both were good answers - and sorry next time I will be more specific. Thank you.

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