Re: drops module (draft)

[Aditya Mahajan <adityam@umich.edu>]

On Thu, 6 Dec 2012, Peter Rolf wrote:

> Hi all,
>
> a first version of the 'drops'-module (MkIV only) is available at
>
> https://www.wuala.com/indiego/public/ConTeXt/drops/?key=caiCGLasLFmJ
>
>
> Taken from the included documentation..
> [..]
> 'drops' is a small extension for ConTeXt, that allows you to add drop
> shadows to rectangular regions (so called boxshadows). A working
> installation of ImageMagick (IM) is required to create the shadow
> graphics. The supported color spaces are CMYK, RGB and Gray, the file
> formats are limited to PNG and JPG.
> [..]
> Read the manual for detailed information.

Nice.

> The attached example is just a small test file for the 'rotation'
> parameter (a compensation for the object rotation, so that the shadow
> stays at the given direction). You will find other examples in the
> documentation and there is also a 'pile' example with the complete
> source. The 'presets' pdf contains the predefined setups for different
> shadow (or frame) types and it's source is a good starting point for
> your own experiments.
>
> This is a first draft, but most things work quite stable. If you want to
> help, test as much as possible. :-)
>
> *You need a recent version of ImageMagick for this module.*

I always thought that shadows were possible to do in PDF 
(after all TikZ does it using some type of PDF primitives). Since you are 
the PDF expert, I am interested in knowing why you choose to go the 
ImageMagic route.

In terms of interface, wouldn't it be better if this somehow interfaced 
with the background/overlay mechanism. For example,

\definedropshadow[identifier][...options...]

which will define an overlay that will call ImageMagic with appropriate 
parameters (and caching the results if speed is a concern),

and then

\externalfigure[name][background=identifier]

should draw a dropped shadow around the image

Aditya
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