On 28-6-2011 2:06, Hans van der Meer wrote:
I would be pleased to get some advice from "color-knowledgeable people" on the
following matter.
In TV-broadcasts there are usually two kinds of subtitles present: Teletext as
characters and DVB as pixels. These can be extracted and rendered with
Metapost. I have done this, but I am not very satisfied with the colors
produced. On the television screen they look bright, when rendered in Metapost
they are dull and muddy. The text is barely readable.
As I am fairly sure I did extract the correct bits from the CLUT contained in
the stream, I wonder if I am doing something not right at the Metapost side. In
the datastream the values given are the most significant 6, 4, 4 and 2 bits of
respectively Y, Cr, Cb, T. These are scaled to the values given to Metapost by
dividing them by 255.
In the zip one finds the program (ConTeXt MKIV) used for typesetting, an
example pixel map with clut, and the output. I would be obliged to get some
comments.
As you're doing a lot of calculations, you can consider using bitmaps
\starttext
\startMPpage
draw
bitmapimage(2,2,"334455 667788 99aabb ccddee")
scaled 3cm
rotated 15 ;
draw
bitmapimage(2,2,"33 55 77 99")
scaled 2cm
rotated 30 ;
draw
bitmapimage(2,2,"0000ff00 ff00ff00 00ff0000 ffff0000")
scaled 1cm
rotated 45 ;
\stopMPpage
\stoptext
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Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
| www.pragma-pod.nl
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