Re: drops module (draft)

[Hans Hagen <pragma@wxs.nl>]

On 12/6/2012 7:05 PM, Aditya Mahajan wrote:
> 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.

Some tricks are possible with functions that repeat bitmap patterns in 
clever ways but I lost the code that does it. If Peter can tell us what 
graphics are needed we can also make them directly as the img library 
has that possibility (we use it in mojca's gnuplot module)

Anyhow, as you are the math magician, here's a start:

\starttext

\startluacode
     local format = string.format
     function document.TestBitmap(nx,ny)
         local r = { }
         local s = 1/nx
         for i=1,ny do
             local c = { }
             for j=1,nx/2 do
                 c[#c+1] = format("%02x",j*s*255)
             end
             for j=nx/2,1,-1 do
                 c[#c+1] = format("%02x",j*s*255)
             end
             c = table.concat(c,"",1,nx)
             r[#r+1] = c
         end
         r = table.concat(r,"\r",1,ny)
         print(r)
         context(r)
     end
\stopluacode

\startMPcode
     draw 
textext("\bitmapimage[x=100,y=100,color=gray]{\ctxlua{document.TestBitmap(100,100)}}") 
xsized 10cm ;
\stopMPcode

\stoptext

So, what's needed is some edge related jugling.

Hans


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