Write a function called blur that blurs the input image. The function is to be called like this:

Question

Namarta Kapil 2019-7-21

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/472647-write-a-function-called-blur-that-blurs-the-input-image-the-function-is-to-be-called-like-this

评论： Image Analyst 2021-6-4

output = blur(img,w);

where img, the input image is a two-dimensional matrix of grayscale pixel values between 0 and 255. Blurring is to be carried out by averaging the pixel values in the vicinity of every pixel. Specifically, the output pixel value is the mean of the pixels in a square submatrix of size 2w+1 where the given pixel sits in the center. For example, if w is 1, then we use a 3x3 matrix, that is, we average all the neighboring pixels of the given pixel and itself. Only use valid pixels when portions of the blurring matrix fall outside the image. For example, the blurred value corresponding to w = 1 at index (1,1) would be the mean of of elements (1,1), (1, 2), (2,1) and (2, 2). Both input img and output output are of type uint8.

You can download the test image here

Opens in new tab

to use in MATLAB.

Code to call your function

img = imread('vandy.png');

output = blur(img,2);

imshow(output);

Can anyone please tell me where I am going wrong with the following code for this question? The code doesnot blur the image and just shows me the image.

function output = blur(img,w)
B=double(img);
[row col] = size(B);
k=2*w+1;
for r=2:row-k
for c=2:col-k
     MeanPixelVal=0;
for r1=r:(r+k-1)
for c1=c:(c+k-1)
MeanPixelVal = MeanPixelVal + double(img(r1,c1));
end
end
MeanPixelVal = MeanPixelVal/(k*k);
blurimg(r,c) = uint8(MeanPixelVal);
end
end
subplot(1,2,1); imshow(img); title('gray image, image intensity 0 - 255');
subplot(1,2,2); imshow(blurimg); str = strcat('blur image, w = ',num2str(w)); title(str);
output = uint8(B);
end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Walter Roberson 2019-7-21

[Merged from https://www.mathworks.com/matlabcentral/answers/472573-write-a-function-called-blur-that-blurs-the-input-image ]

Simple testVariable output has an incorrect value. Tested with a 5x5 uint8 matrix with all 255-s in the first and last rows and columns and zeros everywhere else and w = 1

Assessment result: incorrectUsing image fileVariable output has an incorrect value. Tested with the vandy.png file and w = 1

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Answer 1

Image Analyst 2019-7-21

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https://ww2.mathworks.cn/matlabcentral/answers/472647-write-a-function-called-blur-that-blurs-the-input-image-the-function-is-to-be-called-like-this#answer_384082

You never assign blurimg to B, so B remains the input image that you assigned it to way up at the top.

6 个评论
显示 4更早的评论隐藏 4更早的评论

Namarta Kapil 2019-7-21

NVM this code is not correct for this excercise. I was not supposed to use the imshow function.

Walter Roberson 2019-7-21

imshow() has nothing to do with where you are access B(1,1) .

r starts from 2. r1 starts from r and so has a minimum of 2. You access img(r1,c1) so you never access img(1, anything) . Therefore you cannot possibly be bluring correctly for the first w+1 rows.

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Answer 2

Rohit Patil 2020-5-1

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/472647-write-a-function-called-blur-that-blurs-the-input-image-the-function-is-to-be-called-like-this#answer_429517

编辑：Walter Roberson 2020-5-7

在 MATLAB Online 中打开

function output = blur(img,w)
blurimg=img;
B=blurimg;
[row col] = size(B);
k=2*w+1;
for r=2:row-k
for c=2:col-k
MeanPixelVal=0;
for r1=r:(r+k-1)
for c1=c:(c+k-1)
MeanPixelVal = MeanPixelVal + double(img(r1,c1));
end
end
MeanPixelVal = MeanPixelVal/(k*k);
blurimg(r,c) = uint8(MeanPixelVal);
end
end
subplot(1,2,1); imshow(img); title('gray image, image intensity 0 - 255');
subplot(1,2,2); imshow(blurimg); str = strcat('blur image, w = ',num2str(w)); title(str);
output = uint8(B);
en