I’ve fielded several support calls recently about images in AutoCAD.  They all revolved around AutoCAD’s performance, or lack thereof, in the matter.  Read on to find out how to remedy many of these problems.

Some of the problems were that the images weren’t printing well.  Some had trouble loading a 650MB file (how could they not?).

Coming from a photographic background, I have some insight into the reality of image size and type.  The fact of the matter is a 650MB image is so much overkill it’s not funny.  Using an image of that size on a 24×36 plot is like using a 349E (http://www.cat.com/cda/layout?m=423401&x=7) to fill your kid’s sandbox.

First, let’s talk about image type.  Often firms will receive  a large TIF of an orthophoto.  Given the same resolution, JPG or PNG file are far smaller in size than TIF’s.  True, TIF’s are “technically” better quality, but the compression algorithms for JPG and PNG so good that generally only a trained eye can tell the difference…and that’s at a very high degree of magnification.  And that’s just zoomed in super-tight on your monitor.  You know what?  When you print it, there will be no discernable difference.  Here’s a thread about TIF vs JPG http://www.velocityreviews.com/forums/t250020-tiff-vs-jpg.html

Second, let’s talk about resolution.  Resolution is the single most important attribute of your image that can cause problems in AutoCAD, MS Word, any application that can display and print them.  the fact is, you probably have way more than you need.

In the photographic world, it is accepted that the human eye can discern no more than about 300 pixels per inch when printed on paper.  What does this mean?  Here’s a Wikipedia post about it (yeah I know it’s Wiki, but this pretty much rings true here) http://en.wikipedia.org/wiki/Pixel_density.

The other thing is your printer; it may only be able to resolve 150 pixels per inch, depending on the model.  For an engineering drawing, I would rarely bother to go with anything higher than 150 pixels per inch, but feel free to go a little higher.

You need to do a little math.  Forget about the paper size, think about how big the image is on the paper.  The image below show a white paper outline and a blue image outline.  If the paper in this case is 24×36, the image may be 14×21.  So if you need 150 pixels per in, your image’s resolution at 14×21 would be 2100×3150.  The saved JPG file should be no more than a couple of megabytes.  Super easy for AutoCAD to deal with.

The last thing that may throw a wrench into the mix is georeferencing the image.  Your TIF orthophoto probably came with a world file TFW.  This is what places the image in your coordinate system.  If you have Autodesk Raster Design, this is no problem.  You can resize the image with it and create the new JPG and JGW world file at the same time.  If you don’t have RD, you could attach the TIF, then attach the JPG and overlay it, then remove the TIF.

Hopefully I’ve saved you some trials and tribulations with imaging in AutoCAD.

Matt