From: Hans Hagen <pragma@wxs.nl>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Re: CMYK colors not as expected
Date: Wed, 29 Jun 2011 10:10:58 +0200 [thread overview]
Message-ID: <4E0ADE12.4040104@wxs.nl> (raw)
In-Reply-To: <F882FA36-B82D-4F5F-9E65-34D4151964EE@uva.nl>
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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prev parent reply other threads:[~2011-06-29 8:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-28 12:06 Hans van der Meer
2011-06-29 6:08 ` luigi scarso
2011-06-29 13:59 ` Taco Hoekwater
2011-06-29 14:10 ` Taco Hoekwater
2011-06-29 8:10 ` Hans Hagen [this message]
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