Display image circular by defining the outside of the circle, how?
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Hello, with the following i have plotted a big circle on my image
img = imread('image');
figure,imshow(img)
hold on
Xc= 512; %Center for x
Yc = 512; %Center for y
R = 510; %This is the radius
x=0:0.01:1; %degree
circle=plot(Xc+R*cos(2*pi*x),Yc+R*sin(2*pi*x),'Color','g','LineWidth',0.2);
Now i want to define the outside area of this circle to be transparent (Alpha). How do i tell matlab to only take the outside of the circle and not the hole image. With kind regards, thank you
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Image Analyst
2012년 12월 9일
Feel free to adapt my masking demo:
% Puts up an ellipse and masks and crops the image to the ellipse.
clc; % Clear command window.
% clear; % Delete all variables.
close all; % Close all figure windows except those created by imtool.
imtool close all; % Close all figure windows created by imtool.
workspace; % Make sure the workspace panel is showing.
fontSize = 14;
% Change the current folder to the folder of this m-file.
% (The line of code below is from Brett Shoelson of The Mathworks.)
if(~isdeployed)
cd(fileparts(which(mfilename)));
end
% Change the current folder to the folder of this m-file.
if(~isdeployed)
cd(fileparts(which(mfilename)));
end
% Display images to prepare for the demo.
monochromeImage = imread('pout.tif');
subplot(2, 3, 1);
imshow(monochromeImage);
title('Original Image', 'FontSize', fontSize);
subplot(2, 3, 2);
imshow(monochromeImage);
title('Original Image with ellipse in overlay', 'FontSize', fontSize);
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Image Analysis Demo','numbertitle','off')
%----- Burn ellipse into image -----
% Create elliptical mask, h, as an ROI object over the second image.
subplot(2, 3, 2);
hEllipse = imellipse(gca,[70 15 90 140]); % Second argument defines ellipse shape and position.
% Create a binary image ("mask") from the ROI object.
maskImage = hEllipse.createMask();
% Display the ellipse mask.
subplot(2, 3, 3);
imshow(maskImage);
title('Binary mask of the ellipse', 'FontSize', fontSize);
% Mask the image with the ellipse.
maskedImage = monochromeImage .* cast(maskImage, class(monochromeImage));
% Display the image with the "burned in" ellipse.
subplot(2, 3, 4);
imshow(maskedImage);
title('New image masked by the ellipse', 'FontSize', fontSize);
% Find the bounding box
column1 = find(sum(maskImage, 1), 1, 'first')
column2 = find(sum(maskImage, 1), 1, 'last')
row1 = find(sum(maskImage, 2), 1, 'first')
row2 = find(sum(maskImage, 2), 1, 'last')
croppedImage = maskedImage(row1:row2, column1:column2);
subplot(2, 3, 5);
imshow(croppedImage);
title('Ellipse portion cropped out', 'FontSize', fontSize);
댓글 수: 6
Image Analyst
2012년 12월 12일
이동: DGM
2023년 2월 12일
This is not an answer. You should follow up on my answers with a "comment", not post an answer of your own.
Image Analyst
2012년 12월 9일
Or you can try this demo which is pretty much straight from the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F
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;
img = imread('moon.tif');
subplot(2,2,1);
imshow(img)
axis on;
% Create a logical image of a circle with specified
% diameter, center, and image size.
% First create the image.
[imageSizeY, imageSizeX] = size(img);
[columnsInImage rowsInImage] = meshgrid(1:imageSizeX, 1:imageSizeY);
% Next create the circle in the image.
centerX = 150;
centerY = 225;
radius = 51;
circlePixels = (rowsInImage - centerY).^2 ...
+ (columnsInImage - centerX).^2 <= radius.^2;
% circlePixels is a 2D "logical" array.
% Now, display it.
subplot(2,2,2);
imshow(circlePixels, []);
axis on;
axis image;
title('Binary image of a circle');
% Mask the image. Blacken inside the circle
maskedImage = img; % Initialize
maskedImage(circlePixels) = 0;
subplot(2,2,3);
image(maskedImage) ;
axis on;
axis image;
title('Masked Image');
Rafal Kasztelanic
2012년 12월 9일
편집: Walter Roberson
2012년 12월 10일
Try this:
if true
[x,y] = meshgrid(1024);
c = sqrt((x-Xc).^2+(y-Yc).^2);
img1 = (c>R).*img;
end
RaK
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