How to convert an image to the cartesian X,Y coordinates?

Question

George 2013-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/79590-how-to-convert-an-image-to-the-cartesian-x-y-coordinates

编辑： John Kelly 2014-5-27

采纳的回答： Matt J

I have a grayscale image and i want to convert to the cartesian X,Y coordinates

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Matt J 2013-6-19

编辑：Matt J 2013-6-19

在 MATLAB Online 中打开

Here is a small 3x3 example of a grayscale image

    >> A=diag(randi(255,1,3))
    A =
       233     0     0
         0   162     0
         0     0    25

What would be the result of the "conversion" you are looking for in the case of this image.

George 2013-6-19

1 1 233

1 2 0

1 3 0

2 1 0

2 2 162

2 3 0

3 1 0

3 2 0

3 3 25

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Answer 1

Matt J 2013-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/79590-how-to-convert-an-image-to-the-cartesian-x-y-coordinates#answer_89322

编辑：Matt J 2013-6-19

在 MATLAB Online 中打开

 [x,y]=meshgrid(1:size(A,1), 1:size(A,2));
 result=[x(:),y(:),A(:)];

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Matt J 2013-6-19

编辑：Matt J 2013-6-19

在 MATLAB Online 中打开

Read in as type double

A=double(imread('moon.tif'));

and then,

 result=[x(:),y(:),A(:)];
     >> max(result)
    ans =
       537   358   253

George 2013-6-19

thank you very much Matt J!!!

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Answer 2

Alex Taylor 2013-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/79590-how-to-convert-an-image-to-the-cartesian-x-y-coordinates#answer_89320

编辑：John Kelly 2014-5-27

在 MATLAB Online 中打开

If what you are trying to do is reference a 2-D image to a cartesian coordinate system, you should look at the class imref2d that ships with the Image Processing Toolbox as of R2013a

For example, if you want to reference the image A that Matt mentioned to the default (Intrinsic) coordinate system used by MATLAB in which the center of the first pixel is located at position (1,1) and each pixel has an extent of one unit, you could use the following syntax of imref2d:

    A=diag(randi(255,1,3));
    imref2d(size(A))

ans =

imref2d with properties:
           XWorldLimits: [0.5000 3.5000]
           YWorldLimits: [0.5000 3.5000]
              ImageSize: [3 3]
    PixelExtentInWorldX: 1
    PixelExtentInWorldY: 1
    ImageExtentInWorldX: 3
    ImageExtentInWorldY: 3
       XIntrinsicLimits: [0.5000 3.5000]
       YIntrinsicLimits: [0.5000 3.5000]

imref2d also provides other construction syntaxes and writable properties if you want to reference your image to some other cartesian system.

imref2d provides various methods for converting two and from image subscripts and locations in a continuous cartesian system:

>> methods(imref2d)

Methods for class imref2d:
contains          intrinsicToWorld  worldToIntrinsic  
imref2d           sizesMatch        worldToSubscript

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Answer 3

Jeff E 2013-6-19

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编辑：Jeff E 2013-6-19

在 MATLAB Online 中打开

Unimaginative solution below, possibly with extra computational overhead than a direct solution using reshape and some simple calculations for the X,Y cooridnates.

A=diag(randi(255,1,3))
A =
      10     0     0
       0   226     0
       0     0   233
>> B = true(size(A))
B =
       1     1     1
       1     1     1
       1     1     1
stats = regionprops(B, A, 'PixelValues' , 'PixelList');
PixelListValues = cat(2, [stats.PixelList] , [stats.PixelValues])
PixelListValues =
       1     1    10
       1     2     0
       1     3     0
       2     1     0
       2     2   226
       2     3     0
       3     1     0
       3     2     0
       3     3   233