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Conference hydra::amiga_v1

Title:AMIGA NOTES
Notice:Join us in the *NEW* conference - HYDRA::AMIGA_V2
Moderator:HYDRA::MOORE
Created:Sat Apr 26 1986
Last Modified:Wed Feb 05 1992
Last Successful Update:Fri Jun 06 1997
Number of topics:5378
Total number of notes:38326

2770.0. "Memory for HAM image?" by BPOV06::I_SHAW (I hate LJ252-Amiga problems.) Thu Jul 27 1989 18:50

	Can someone please tell me exactly how much a 640x400 HAM image eats
out of memory (how many K)?

thanks,
--mikie--
T.RTitleUserPersonal
Name
DateLines
2770.1How about this...SMAUG::SPODARYKScaring the pedestrians...Thu Jul 27 1989 19:0210
    Hmn, you can't do a 640x400 HAM image.  How about a 320x400 HAM image?
    
    320 x 400 x 6 (HAM = 6 bit planes) = 768000 bits
                                       = 96000  Bytes 
                                       = 93.75  KB
    
    -Steve (it makes sense to me) 
    
    If you're displaying the image in a screen or window, there is some
    additional overhead.
2770.2Oops, I'm asleep...SMAUG::SPODARYKScaring the pedestrians...Thu Jul 27 1989 19:1812
    Oh well.  Is it Friday yet?
    
    HAM uses 12 bits to determine the color per pixel.  So you 
    really reserve 640 x 400 x 6 bit planes.  HAM then uses a pair of
    6 bits per pixel, and reduces the effective resolution to 320 x 400.
    So, however you look at it, its a substansial amount of memory.
    
    320 x 400 x 12 ( 2^12 = 4096 colors ) = 1536000 bits
                                          = 192000  Bytes 
                                          = 187.5   KB
                        
    See HAM discussions elsewhere...                  
2770.3ANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESThu Jul 27 1989 19:223
    both wrong.
    I'll quote the manual later.
    tom
2770.4I vote for .1TLE::RMEYERSRandy MeyersThu Jul 27 1989 20:3413
Re: .2

HAM only uses 6 bits per pixel total.  It gets the effect of 12 bits per
pixel by encoding this pixel as a delta from the previous pixel (2 bit
command to replace the R, G, or B component of the previous pixel or to
load the color from one of the first 16 color registers).

Re: .3

>   both wrong [referring to .1 and .2].
>   I'll quote the manual later.

I can always be proven wrong, but I agree with the statements in .1.
2770.5I agree, .1 is correctTALLIS::MCAFEESteve McAfeeThu Jul 27 1989 21:440
2770.6never mind....ANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESThu Jul 27 1989 23:3216
    Now I'm going to show you all.  This will teach you:
    
    Amiga Hardware Reference Manual page 38:
    "Note that in high-resolution mode, you can have up to four bit-planes
    in the playfield and, therefore, up to 16 colors."
    
    From the Scuplt 3D manual: page 18:
    "If your imaging method employs Hold and Modify (HAM) grpahics in
    order to use 4096 colors, the image that is displayed will be in
    LO-RES"    
    
    So .1 is right and I was wrong.  This will teach you not to shoot
    from the hip, but to carefully be certain of what you say about
    technical details.
    
    Tom    
2770.7Wait for me :-)FRAMBO::BALZERChristian Balzer DTN:785-1029Fri Jul 28 1989 06:519
    
    Re: * 
    
    Darn, why do these interesting and funny discussions always happen
    when I'm already home or getting hopelessly drunk???
    
    I vote for a bann of the time zones.....   :-) :-)
    
    <CB>
2770.8Ignore Time ZonesTLE::RMEYERSRandy MeyersFri Jul 28 1989 20:597
Re: .7

>    Darn, why do these interesting and funny discussions always happen
>    when I'm already home or getting hopelessly drunk???

Just do what I do, enter a reply anyway and pretend you didn't know
that someone else already answered.  :-)
2770.9clean-upHYSTER::DEARBORNTrouvez MieuxMon Jul 31 1989 16:174
Now, why don't we delete replies .2 thru .9?

Randy

2770.10Whose to judge what notes will die?ANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESMon Jul 31 1989 16:2310
>    < Note 2770.9 by HYSTER::DEARBORN "Trouvez Mieux" >
 >                                -< clean-up >-
>
>Now, why don't we delete replies .2 thru .9?
>
>Randy
 Because .6 is the only one that quotes the documentation, and therefore
    is the
    only one you can trust.
    Tom