Author Topic: LISP to measure photo  (Read 1557 times)

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AUTOKAD

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LISP to measure photo
« on: October 21, 2008, 11:07:52 AM »
I have jpg photo from a survey that we did. If I insert this image to cad, is there a lisp or a way to measure it from the photo. (ie. size of tiles, ceiling heights, etc..)

If im not mistaken this can be done in photoshop, so there got to be a way to do it in cad. Thank you.

M-dub

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Re: LISP to measure photo
« Reply #1 on: October 21, 2008, 11:10:59 AM »
Don't know if a lisp would do you any good if the photo isn't scaled... and good luck with that!

...well, I guess it all depends on the accuracy you're looking for.

Matt__W

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Re: LISP to measure photo
« Reply #2 on: October 21, 2008, 11:11:30 AM »
Don't know if a lisp would do you any good if the photo isn't scaled... and good luck with that!

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Re: LISP to measure photo
« Reply #3 on: October 21, 2008, 11:19:22 AM »
It seems that if you have a known dimension, you ought to be able scale the image. You can bring the image, pixel by pixel ,using something like this.

http://www.theswamp.org/index.php?topic=22296.msg268472#msg268472 :)

CAB

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Re: LISP to measure photo
« Reply #4 on: October 21, 2008, 11:19:54 AM »
No Lisp.

The way I handle photos is to identify something I know the dimension of.
Draw a line to match the length & angle of that object.
Use the ALIGN command to pick the spot on the photo, then the end of the line
again with the other end in the photo & then the line.
Say YES to scale and the photo is rotated & scaled to match the line.
At his point the photo is the correct scale & you can use the DIST command
to measure objects. Note that snaps are of no use.
I typically draw over the photo to create real objects.
It all depends what your ultimate goal is.

There are programs that will Vectorize the photo as well.
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Bob Wahr

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Re: LISP to measure photo
« Reply #5 on: October 21, 2008, 11:39:06 AM »
Keep in mind also that a photo is not a flat plane projection.  Using CAB's method (which is about the only way) will have you accurate along the line that you aligned to only.  The further you get from that line the larger your error.

M-dub

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Re: LISP to measure photo
« Reply #6 on: October 21, 2008, 11:41:49 AM »
Yes, 'perspective' planes and lens distortion will screw your measurements up a bit.