Importing a JPEG of known real dimensions

[Leont]

Hi,

Im looking for help on how to import a jpeg image of known size, by this I mean the DPI resolution has been set in the EXIF header, so that the intended physical size of the actual jpeg image in known.

I understand this when outputting the image, so that the printer knows how big to make the final print.
But I want to import this JPEG into SU so that it appears as the correct physical size.

The attachment file has the EXIF resolution set so the physical size should be 90 x 120 inches. Ive tested this file in other CAD and its read ok

Ive noticed in SU, that importing images with different EXIF resolutions appear as different sizes, so its reading something. But I cant figure out exactly how it works

Im looking at building a new output for a photogrammetric camera called Spike (http://www.ikegps.com/spike) to enable direct measurements from photos in CAD

thanks

Leon

[JQL]

The way I do it is accurate but completelly indiferent to exif:

• Import the img into sketchup;
• Draw a line on top of it that you know the size of (if you know the overall size of the image even better);
• Group the image and the line;
• Edit the group;
• Use tape measure on the line;
• It should read some random distance in the VCB;
• Right after clicking on the second point, type the distance you want that line to be;
• Both line and image (and everything inside the group) will scale porportionally so that the line is at the size of your input.

[Leont]

So a little more info, I looking for an automatic way of doing this, so that I can improve the Spike photogrammetic camera product.

We are prototyping a special Jpeg output from the Spike.
The Jpeg will be deskewed, eg the measurement surface, which is usually oblique to the camera, will be flattened.
Then we compute a resolution in DPI for the measurement surface, and apply this to the JPEG EXIF resolution fields.

The idea, is that a CAD package imports the JPEG, reads the resolutions and presents the image with the correct physical measurements.

This is intended to be a standard output, so for example, users can photograph the side of a building, put it into the CAD, and measure directly.

Ive tested the concept in CorelDraw, which our Signage customer base use, and it works really well, it reads JPEG resolutions, get the image to the right size and makes downstream design work a lot simpler.