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Old 25 June 2013, 23:18   #33
pandy71
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Join Date: Jun 2010
Location: PL
Posts: 1,546
Quote:
Originally Posted by kovacm View Post
@pandy71

offtopic - I am curious: how these images are reproduced on Amiga?

My first guess is "Spectrum 512" in hi-res (palette changing trick)? right?
Yes, good guess (educated one) - this is PCHG Hires Interlace - HAMLAB (converter) + MOSTRA (viewer) - some limitations make this good only for particular group of images (color changes should be oriented in vertical direction) - but for example city landscape is made from 611 unique colors.
Sometimes better effects can be achieved with hybrid solution: http://www.ximagic.com/q_index.html with HAMLAB (Ximagic Quantizer preproces image to reduced amount of colours, then HAMLAB trying to fit this in PCHG limitations - dithereing/noise shaping is extremally important and HAMLAB have some limitations also seems that is not very stable in terms of quality) - however using smart (psycho-visually tuned - shape recognition? - neural networks?) or at least decent modern (http://members.ozemail.com.au/~dekker/NEUQUANT.HTML , http://moonflare.com/code/scolorq/) color reduction algorithm horizontally oriented (to fit optimally in Copper limitations) with some direct hardware access (PCHG is a bit limited to made standard OS friendly - interlace offer less color changes on screen), probably those results can be much better, perhaps near perfect-optimal.

As there is no PCHG compatible viewer for PC (i don't know such viewer) , those pictures are changed from PCHG IFF to 24 bit png by HAMLAB - this can be seen as loss free conversion thus WYSIWYG.

http://ulozto.net/xFt2Afu2/pchg-7z some examples in PCHG IFF (thus Amiga or WinUAE required with at least freeware Mostra)
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