pixel to mm

[pam]

Hi all,
I'm working with images for face reconigition and I need to take some
mesures. I can get the measure like diference between pixels but I
need to do some calculation so I need the measures on mm so I would
like to know if I'm in the right way

I have an jpg image with 96 resolution on horizontal and vertical
so for every pixel I can do

96 pixel ------ 1 inch ---- 25.4 mm
1 pixel ---- 0.010417 inch ----- 0.2645 mm

so If I have 30 pixel it's 30 * 0.2645 (this in mm) ??

There is another way to calculate it?

Thanks in advance

Pamela

[yongkang wong]

Hi Pam,

I'm afraid you are doing something very dangerous here. Please check
with your image and be sure all of them are taken with same distance
between camera and faces.

It is really harsh to say 96 pixel == 1 inch. If the camera move back
for 1 meter, 96 pixel will not be 1 inch.

But if you think that is not an issue, what you have is probably a
right.

cheers,
yongkang

[pam]

I'm sure the image are taken from same distance between cameras and faces.
But anyway I think I'm wrong anyway because I say 96 pixel == 1inch
because the image are 96 pixel per inch
wich could not be the real measure.
So How could I make measure on the 2D image? Any tutorial or book to recomend?

Thanks in advance
Pamela

2009/6/22 yongkang wong <yongka...@gmail.com>: