>Note: I am use a traslator.
>
>Please, some of you can inform me as converting correctly from pixeles to millimeters and vice versa. Try to make it calculating the values they show in the properties of an image in several edition programs of graphics, but I have not been able to give with it formulates it correct.
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>*-- Original
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>Por favor, alguno de ustedes me puede informar como convertir correctamente de pixeles a milimetros y viceversa. Intente hacerlo calculando los valores dque muestran en las propiedades de una imagen en varios programas de edicion de graficos, pero no he logrado dar con la formula correcta.

I don't believe you can do this with any accuracy. You would have to know the size of the pixel and the spacing between pixels which can vary depending on the display.

Regad,
Mike