MATLAB: Drawing circles in mm on an image

circleconvertimage

Hello community,

I want to draw circles with specific sizes in mm on an image.

So that if I would print out the image, the radius of the circles would appear in the same mm I used for drawing the circles. The picture is 480×720 in size and has 300dpi.

Can someone give me an advise?

Thanks in advance!

Best Answer

Picture size is irrelevant here. only resolution, if I get your question right. DPI is dots per inches, one inch is 25.4mm, meaning you have density of 300/25.4 = 11.8 dots (or pixels) per mm. So if you want to draw a circle of X mm radius, it should have radius of X*11.8 dots.

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doc meshgrid

to generate xdata and ydata that can correspond to any unit you like.

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Just multiply the row index of the points by the ratio of the row sizes, and the column index by the ratio of the column sizes.

[rowsa, columnsa, numColorsa] = size(imageA);
[rowsb, columnsb, numColorsa] = size(imageB);
% Transform point 1
row1b = round(row1a * rowsb / rowsa);
col1b = round(col1a * columnsb / columnsb);

Same for any other points, like the other 3 vertex points.

Best Answer

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