can you crop triangles,quadrilaterals

In Aperture you only can crop rectangulare sections. The "lasso" tool requires layers and transparency; that is not supported by Aperture. Aperture deals with image preprocessing and maintaining an image database, not with image compositing. For this you are supposed to use plug-ins or external editors, you might give the free "Gimp" a try as an external editor, or Pixelmator , or Photoshop.

Any graphics program will likely suffice. The costs span the gamut from free to Photoshop-like expensive 🙂 . Even OS X's Preview has Instant-Alpha and a Lasso built in:

(screenshot)

As you work with cut-outs, keep in mind that the image file is actually a rectangle -- it's just that all the pixels that are outside the designated shape are transparent.

rdadd wrote:

thanks..looks like I have to get photoshop

PS is unreasonably expensive and too complex to be the best choice for most photogs. Like Léonie said "give the free "Gimp" a try as an external editor, or Pixelmator..." If you do not intend a full-time career in graphic arts I would try those two first rather than jumping into expensive/complex full Photoshop.

-Allen