How to create a white mask?

Question

Jessica 2018-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/387508-how-to-create-a-white-mask

评论： Jessica 2018-3-10

I am using the below code to overlay a black, elliptical mask around an imported photo. Rather than having the imported photo surrounded by black, is there a way to change the black background color to white?

I = imread (ConvertFileName);

%# Create an ellipse shaped mask c = fix(size(I) / 2); %# Ellipse center point (y, x) r_sq = [76, 100] .^ 2; %# Ellipse radii squared (y-axis, x-axis) [X, Y] = meshgrid(1:size(I, 2), 1:size(I, 1)); ellipse_mask = (r_sq(2) * (X - c(2)) .^ 2 + r_sq(1) * (Y - c(1)) .^ 2 <= prod(r_sq));

%# Apply the mask to the image I_cropped = bsxfun(@times, I, uint8(ellipse_mask)); imshow(I_cropped)

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Answer 1

Image Analyst 2018-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/387508-how-to-create-a-white-mask#answer_309412

mask_and_crop_image_by_ellipse.m

See my attached demo.

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Jessica 2018-3-10

Thanks for uploading this. When I run the script, the background is still black. Is there a way to modify my code to just reverse the colors? The other issue is that I want to save the image with the same quality as the original image. I've been doing that with the code I pasted above with:

Filename=ConvertFileName; export_fig TempFigure.jpg -r300; B=imread('TempFigure.jpg');imwritesize(B, Filename, 2.14, 300); %Save file with 2.14 inch width and 300 dpi delete('TempFigure.jpg'); close all;

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