Drawing circles in mm on an image

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 480x720 in size and has 300dpi.

Can someone give me an advise?

Thanks in advance!

Answer 1

[Arie Lerner]

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.

[Rodi Ak]

Thank you! I was not sure whether dots is the same as pixels, but then it is just basic mathematics.