Cadalyst contributing author (and close friend of Captain LearnCurve) Bill Fane provided us a with a way to insert raster image files whose aspect ratios are out of sync.
"Problem: You want to insert a raster image into a drawing, perhaps to trace over it with AutoCAD lines, circles, arcs, etc., but the aspect (width to height) ratio of the raster image isn't correct. Unfortunately, although inserting a raster image seems to be almost identical to inserting a block, you can't specify different x and y scale factors.
"Solution: Insert the image at the default 1:1 ratio, and then create a block that includes the image as a component of the block. Now insert the block with different x and y scale factors. Bingo! The image stretches appropriately.
"Interestingly, competitive brands of 'compatible' software will allow raster images to be inserted directly with different x and y scale factors. More interestingly, AutoCAD will honor the different scale factors if you then open the drawing in AutoCAD. Even more interestingly, if you Explode the block back to being an inserted raster image, then AutoCAD still honors the different x and y scale factors.
"And here is another method of importing raster images whose aspect ratio is wrong: Simply open the image in Paint, click on Image, then on Stretch/Skew, and change the Horizontal or Vertical value to correct the problem. Save or Save As, and then import into AutoCAD."
Notes from Cadalyst Tip Patrol: Images in AutoCAD are great; blocks are too. Converting your data (of any type) into a block provides more settings to play with, or at least different ones. Although Bill's tip is a great use of blocks to fix problems, you can also use this tip to create a unique exaggerated view or detail. For example, the changes in elevation on a roadway cross section might not be noticeable. Many sections will have a different vertical scale than the horizontal, in order to exaggerate the changes in elevations. This makes them visible. Draw your section to scale, then block it. Insert it with a different vertical scale!