How to make circular black frame in image?
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Hi, I'm trying to make a circular black frame on an image in matlab. I have figured out how to make a rectangular frame, but I can't figure how to make a circular frame. Heres the code:
im = imread('michelle_pf.jpeg');
imshow(im)
[h,w,kanaler] = size(im);
im_k = im(1:min(h,w),1:min(h,w),:);
figure(2),clf
imshow(im_k)
[h,w,kanaler] = size(im_k);
im_g = rgb2gray(im_k);
im_d = im2double(im_g);
storleik_ramme = 50;
for i=1:h
for j=1:w
if i<storleik_ramme || j<storleik_ramme || j>w-storleik_ramme || i>h-storleik_ramme
im_d(i,j)=0.0;
end
end
end
figure(3),clf
imshow(im_d)
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Antworten (1)
Image Analyst
am 9 Nov. 2012
Bearbeitet: Image Analyst
am 9 Nov. 2012
See my demo. It's not really so complicated. I basically just fancied up the short snippet in the FAQ. http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F So, just copy, paste, and run.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
imtool close all; % Close all imtool figures.
clear; % Erase all existing variables.
workspace; % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;
% Read in a standard MATLAB color demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'peppers.png';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
% Didn't find it there. Check the search path for it.
fullFileName = baseFileName; % No path this time.
if ~exist(fullFileName, 'file')
% Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist.', fullFileName);
uiwait(warndlg(errorMessage));
return;
end
end
rgbImage = imread(fullFileName);
% Display the original image.
subplot(2, 2, 1);
imshow(rgbImage);
title('Original Color Image', 'FontSize', fontSize);
[rows columns numberOfColorChannels] = size(rgbImage);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Create a logical image of a circle with specified
% diameter, center, and image size.
% First create the image.
[columnsInImage rowsInImage] = meshgrid(1:columns, 1:rows);
% Next create the circle in the center of the image.
centerX = columns/2;
centerY = rows/2;
radius = min([rows columns]) / 2;
circlePixels = (rowsInImage - centerY).^2 ...
+ (columnsInImage - centerX).^2 <= radius.^2;
% circlePixels is a 2D "logical" array.
% Now, display it.
subplot(2, 2, 2);
imshow(circlePixels, []);
colormap([0 0 0; 1 1 1]);
title('Binary image of a circle', 'FontSize', fontSize);
% Mask the image.
maskedRgbImage = bsxfun(@times, rgbImage, cast(circlePixels, class(rgbImage)));
% Now, display it.
subplot(2, 2, 3);
imshow(maskedRgbImage);
title('Image Masked by the Circle', 'FontSize', fontSize);
% Mask the image the other way.
maskedRgbImage = bsxfun(@times, rgbImage, cast(~circlePixels, class(rgbImage)));
% Now, display it.
subplot(2, 2, 4);
imshow(maskedRgbImage);
title('Image Masked by the Circle', 'FontSize', fontSize);
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