On 2012–12–06 Aditya Mahajan wrote:
I always thought that shadows were possible to do in PDF (after all TikZ does it using some type of PDF primitives).
It is. I use MetaPost to draw the shadows using the shading mechanism: withshading("circular", urcorner bottom_left, urcorner bottom_left, radius, 0) withfromshadecolor \MPcolor{c:transparent} withtoshadecolor col; and it works well if placed in an overlay. However, I did not manage to get it working in TikZ, it could not display shadings to transparent colours (which is very handy for slides where the shadings might overlay graphics with a non-uniform colour).
Since you are the PDF expert, I am interested in knowing why you choose to go the ImageMagic route.
From my experience shadows made from MetaPost shadings (which uses PDF shadings, I assume) are quite low level. It's harder to get the angle, distance and shadow size correctly implemented. I think the ImageMagick shadings are more high level and ready to use.
Marco