Color shifts using QUANTIZE_COLORS=256

rich.fromm nospam420 at YAHOO.COM
Fri Nov 30 12:37:01 PST 2007


rich.fromm wrote:
> 
> ALL that I'm
> attempting to displaying here is an 80% grey background.  This works fine
> with
> both the AGG and GD rendering backends, as long as quantization is not
> enabled.  However, if I enable quantization, instead of getting a uniform
> background of (204,204,204), I get (204,206,204).
> 

here's another little tidbit.  i iterated through all possible grey
backgrounds from (0,0,0) through (255,255,255).  in not one case did
mapserver
return a pure grey background.  the green was always shifted by -2 or +2
relative to the red and the blue.

- Rich

[rich at peyote bg 12:30:14]$ for c in `seq 0 255`; do ~joe/bin/colorhist
agg_q.${c}grey.png; done
agg_q.0grey.png --------
0: (  4,  2,  4)        #040204
agg_q.1grey.png --------
0: (  4,  2,  4)        #040204
agg_q.2grey.png --------
0: (  4,  2,  4)        #040204
agg_q.3grey.png --------
0: (  4,  2,  4)        #040204
agg_q.4grey.png --------
0: (  4,  6,  4)        #040604
agg_q.5grey.png --------
0: (  4,  6,  4)        #040604
agg_q.6grey.png --------
0: (  4,  6,  4)        #040604
agg_q.7grey.png --------
0: (  4,  6,  4)        #040604
agg_q.8grey.png --------
0: ( 12, 10, 12)        #0C0A0C
agg_q.9grey.png --------
0: ( 12, 10, 12)        #0C0A0C
agg_q.10grey.png --------
0: ( 12, 10, 12)        #0C0A0C
agg_q.11grey.png --------
0: ( 12, 10, 12)        #0C0A0C
agg_q.12grey.png --------
0: ( 12, 14, 12)        #0C0E0C
agg_q.13grey.png --------
0: ( 12, 14, 12)        #0C0E0C
agg_q.14grey.png --------
0: ( 12, 14, 12)        #0C0E0C
agg_q.15grey.png --------
0: ( 12, 14, 12)        #0C0E0C
agg_q.16grey.png --------
0: ( 20, 18, 20)        #141214
agg_q.17grey.png --------
0: ( 20, 18, 20)        #141214
agg_q.18grey.png --------
0: ( 20, 18, 20)        #141214
agg_q.19grey.png --------
0: ( 20, 18, 20)        #141214
agg_q.20grey.png --------
0: ( 20, 22, 20)        #141614
agg_q.21grey.png --------
0: ( 20, 22, 20)        #141614
agg_q.22grey.png --------
0: ( 20, 22, 20)        #141614
agg_q.23grey.png --------
0: ( 20, 22, 20)        #141614
agg_q.24grey.png --------
0: ( 28, 26, 28)        #1C1A1C
agg_q.25grey.png --------
0: ( 28, 26, 28)        #1C1A1C
agg_q.26grey.png --------
0: ( 28, 26, 28)        #1C1A1C
agg_q.27grey.png --------
0: ( 28, 26, 28)        #1C1A1C
agg_q.28grey.png --------
0: ( 28, 30, 28)        #1C1E1C
agg_q.29grey.png --------
0: ( 28, 30, 28)        #1C1E1C
agg_q.30grey.png --------
0: ( 28, 30, 28)        #1C1E1C
agg_q.31grey.png --------
0: ( 28, 30, 28)        #1C1E1C
agg_q.32grey.png --------
0: ( 36, 34, 36)        #242224
agg_q.33grey.png --------
0: ( 36, 34, 36)        #242224
agg_q.34grey.png --------
0: ( 36, 34, 36)        #242224
agg_q.35grey.png --------
0: ( 36, 34, 36)        #242224
agg_q.36grey.png --------
0: ( 36, 38, 36)        #242624
agg_q.37grey.png --------
0: ( 36, 38, 36)        #242624
agg_q.38grey.png --------
0: ( 36, 38, 36)        #242624
agg_q.39grey.png --------
0: ( 36, 38, 36)        #242624
agg_q.40grey.png --------
0: ( 44, 42, 44)        #2C2A2C
agg_q.41grey.png --------
0: ( 44, 42, 44)        #2C2A2C
agg_q.42grey.png --------
0: ( 44, 42, 44)        #2C2A2C
agg_q.43grey.png --------
0: ( 44, 42, 44)        #2C2A2C
agg_q.44grey.png --------
0: ( 44, 46, 44)        #2C2E2C
agg_q.45grey.png --------
0: ( 44, 46, 44)        #2C2E2C
agg_q.46grey.png --------
0: ( 44, 46, 44)        #2C2E2C
agg_q.47grey.png --------
0: ( 44, 46, 44)        #2C2E2C
agg_q.48grey.png --------
0: ( 52, 50, 52)        #343234
agg_q.49grey.png --------
0: ( 52, 50, 52)        #343234
agg_q.50grey.png --------
0: ( 52, 50, 52)        #343234
agg_q.51grey.png --------
0: ( 52, 50, 52)        #343234
agg_q.52grey.png --------
0: ( 52, 54, 52)        #343634
agg_q.53grey.png --------
0: ( 52, 54, 52)        #343634
agg_q.54grey.png --------
0: ( 52, 54, 52)        #343634
agg_q.55grey.png --------
0: ( 52, 54, 52)        #343634
agg_q.56grey.png --------
0: ( 60, 58, 60)        #3C3A3C
agg_q.57grey.png --------
0: ( 60, 58, 60)        #3C3A3C
agg_q.58grey.png --------
0: ( 60, 58, 60)        #3C3A3C
agg_q.59grey.png --------
0: ( 60, 58, 60)        #3C3A3C
agg_q.60grey.png --------
0: ( 60, 62, 60)        #3C3E3C
agg_q.61grey.png --------
0: ( 60, 62, 60)        #3C3E3C
agg_q.62grey.png --------
0: ( 60, 62, 60)        #3C3E3C
agg_q.63grey.png --------
0: ( 60, 62, 60)        #3C3E3C
agg_q.64grey.png --------
0: ( 68, 66, 68)        #444244
agg_q.65grey.png --------
0: ( 68, 66, 68)        #444244
agg_q.66grey.png --------
0: ( 68, 66, 68)        #444244
agg_q.67grey.png --------
0: ( 68, 66, 68)        #444244
agg_q.68grey.png --------
0: ( 68, 70, 68)        #444644
agg_q.69grey.png --------
0: ( 68, 70, 68)        #444644
agg_q.70grey.png --------
0: ( 68, 70, 68)        #444644
agg_q.71grey.png --------
0: ( 68, 70, 68)        #444644
agg_q.72grey.png --------
0: ( 76, 74, 76)        #4C4A4C
agg_q.73grey.png --------
0: ( 76, 74, 76)        #4C4A4C
agg_q.74grey.png --------
0: ( 76, 74, 76)        #4C4A4C
agg_q.75grey.png --------
0: ( 76, 74, 76)        #4C4A4C
agg_q.76grey.png --------
0: ( 76, 78, 76)        #4C4E4C
agg_q.77grey.png --------
0: ( 76, 78, 76)        #4C4E4C
agg_q.78grey.png --------
0: ( 76, 78, 76)        #4C4E4C
agg_q.79grey.png --------
0: ( 76, 78, 76)        #4C4E4C
agg_q.80grey.png --------
0: ( 84, 82, 84)        #545254
agg_q.81grey.png --------
0: ( 84, 82, 84)        #545254
agg_q.82grey.png --------
0: ( 84, 82, 84)        #545254
agg_q.83grey.png --------
0: ( 84, 82, 84)        #545254
agg_q.84grey.png --------
0: ( 84, 86, 84)        #545654
agg_q.85grey.png --------
0: ( 84, 86, 84)        #545654
agg_q.86grey.png --------
0: ( 84, 86, 84)        #545654
agg_q.87grey.png --------
0: ( 84, 86, 84)        #545654
agg_q.88grey.png --------
0: ( 92, 90, 92)        #5C5A5C
agg_q.89grey.png --------
0: ( 92, 90, 92)        #5C5A5C
agg_q.90grey.png --------
0: ( 92, 90, 92)        #5C5A5C
agg_q.91grey.png --------
0: ( 92, 90, 92)        #5C5A5C
agg_q.92grey.png --------
0: ( 92, 94, 92)        #5C5E5C
agg_q.93grey.png --------
0: ( 92, 94, 92)        #5C5E5C
agg_q.94grey.png --------
0: ( 92, 94, 92)        #5C5E5C
agg_q.95grey.png --------
0: ( 92, 94, 92)        #5C5E5C
agg_q.96grey.png --------
0: (100, 98,100)        #646264
agg_q.97grey.png --------
0: (100, 98,100)        #646264
agg_q.98grey.png --------
0: (100, 98,100)        #646264
agg_q.99grey.png --------
0: (100, 98,100)        #646264
agg_q.100grey.png --------
0: (100,102,100)        #646664
agg_q.101grey.png --------
0: (100,102,100)        #646664
agg_q.102grey.png --------
0: (100,102,100)        #646664
agg_q.103grey.png --------
0: (100,102,100)        #646664
agg_q.104grey.png --------
0: (108,106,108)        #6C6A6C
agg_q.105grey.png --------
0: (108,106,108)        #6C6A6C
agg_q.106grey.png --------
0: (108,106,108)        #6C6A6C
agg_q.107grey.png --------
0: (108,106,108)        #6C6A6C
agg_q.108grey.png --------
0: (108,110,108)        #6C6E6C
agg_q.109grey.png --------
0: (108,110,108)        #6C6E6C
agg_q.110grey.png --------
0: (108,110,108)        #6C6E6C
agg_q.111grey.png --------
0: (108,110,108)        #6C6E6C
agg_q.112grey.png --------
0: (116,114,116)        #747274
agg_q.113grey.png --------
0: (116,114,116)        #747274
agg_q.114grey.png --------
0: (116,114,116)        #747274
agg_q.115grey.png --------
0: (116,114,116)        #747274
agg_q.116grey.png --------
0: (116,118,116)        #747674
agg_q.117grey.png --------
0: (116,118,116)        #747674
agg_q.118grey.png --------
0: (116,118,116)        #747674
agg_q.119grey.png --------
0: (116,118,116)        #747674
agg_q.120grey.png --------
0: (124,122,124)        #7C7A7C
agg_q.121grey.png --------
0: (124,122,124)        #7C7A7C
agg_q.122grey.png --------
0: (124,122,124)        #7C7A7C
agg_q.123grey.png --------
0: (124,122,124)        #7C7A7C
agg_q.124grey.png --------
0: (124,126,124)        #7C7E7C
agg_q.125grey.png --------
0: (124,126,124)        #7C7E7C
agg_q.126grey.png --------
0: (124,126,124)        #7C7E7C
agg_q.127grey.png --------
0: (124,126,124)        #7C7E7C
agg_q.128grey.png --------
0: (132,130,132)        #848284
agg_q.129grey.png --------
0: (132,130,132)        #848284
agg_q.130grey.png --------
0: (132,130,132)        #848284
agg_q.131grey.png --------
0: (132,130,132)        #848284
agg_q.132grey.png --------
0: (132,134,132)        #848684
agg_q.133grey.png --------
0: (132,134,132)        #848684
agg_q.134grey.png --------
0: (132,134,132)        #848684
agg_q.135grey.png --------
0: (132,134,132)        #848684
agg_q.136grey.png --------
0: (140,138,140)        #8C8A8C
agg_q.137grey.png --------
0: (140,138,140)        #8C8A8C
agg_q.138grey.png --------
0: (140,138,140)        #8C8A8C
agg_q.139grey.png --------
0: (140,138,140)        #8C8A8C
agg_q.140grey.png --------
0: (140,142,140)        #8C8E8C
agg_q.141grey.png --------
0: (140,142,140)        #8C8E8C
agg_q.142grey.png --------
0: (140,142,140)        #8C8E8C
agg_q.143grey.png --------
0: (140,142,140)        #8C8E8C
agg_q.144grey.png --------
0: (148,146,148)        #949294
agg_q.145grey.png --------
0: (148,146,148)        #949294
agg_q.146grey.png --------
0: (148,146,148)        #949294
agg_q.147grey.png --------
0: (148,146,148)        #949294
agg_q.148grey.png --------
0: (148,150,148)        #949694
agg_q.149grey.png --------
0: (148,150,148)        #949694
agg_q.150grey.png --------
0: (148,150,148)        #949694
agg_q.151grey.png --------
0: (148,150,148)        #949694
agg_q.152grey.png --------
0: (156,154,156)        #9C9A9C
agg_q.153grey.png --------
0: (156,154,156)        #9C9A9C
agg_q.154grey.png --------
0: (156,154,156)        #9C9A9C
agg_q.155grey.png --------
0: (156,154,156)        #9C9A9C
agg_q.156grey.png --------
0: (156,158,156)        #9C9E9C
agg_q.157grey.png --------
0: (156,158,156)        #9C9E9C
agg_q.158grey.png --------
0: (156,158,156)        #9C9E9C
agg_q.159grey.png --------
0: (156,158,156)        #9C9E9C
agg_q.160grey.png --------
0: (164,162,164)        #A4A2A4
agg_q.161grey.png --------
0: (164,162,164)        #A4A2A4
agg_q.162grey.png --------
0: (164,162,164)        #A4A2A4
agg_q.163grey.png --------
0: (164,162,164)        #A4A2A4
agg_q.164grey.png --------
0: (164,166,164)        #A4A6A4
agg_q.165grey.png --------
0: (164,166,164)        #A4A6A4
agg_q.166grey.png --------
0: (164,166,164)        #A4A6A4
agg_q.167grey.png --------
0: (164,166,164)        #A4A6A4
agg_q.168grey.png --------
0: (172,170,172)        #ACAAAC
agg_q.169grey.png --------
0: (172,170,172)        #ACAAAC
agg_q.170grey.png --------
0: (172,170,172)        #ACAAAC
agg_q.171grey.png --------
0: (172,170,172)        #ACAAAC
agg_q.172grey.png --------
0: (172,174,172)        #ACAEAC
agg_q.173grey.png --------
0: (172,174,172)        #ACAEAC
agg_q.174grey.png --------
0: (172,174,172)        #ACAEAC
agg_q.175grey.png --------
0: (172,174,172)        #ACAEAC
agg_q.176grey.png --------
0: (180,178,180)        #B4B2B4
agg_q.177grey.png --------
0: (180,178,180)        #B4B2B4
agg_q.178grey.png --------
0: (180,178,180)        #B4B2B4
agg_q.179grey.png --------
0: (180,178,180)        #B4B2B4
agg_q.180grey.png --------
0: (180,182,180)        #B4B6B4
agg_q.181grey.png --------
0: (180,182,180)        #B4B6B4
agg_q.182grey.png --------
0: (180,182,180)        #B4B6B4
agg_q.183grey.png --------
0: (180,182,180)        #B4B6B4
agg_q.184grey.png --------
0: (188,186,188)        #BCBABC
agg_q.185grey.png --------
0: (188,186,188)        #BCBABC
agg_q.186grey.png --------
0: (188,186,188)        #BCBABC
agg_q.187grey.png --------
0: (188,186,188)        #BCBABC
agg_q.188grey.png --------
0: (188,190,188)        #BCBEBC
agg_q.189grey.png --------
0: (188,190,188)        #BCBEBC
agg_q.190grey.png --------
0: (188,190,188)        #BCBEBC
agg_q.191grey.png --------
0: (188,190,188)        #BCBEBC
agg_q.192grey.png --------
0: (196,194,196)        #C4C2C4
agg_q.193grey.png --------
0: (196,194,196)        #C4C2C4
agg_q.194grey.png --------
0: (196,194,196)        #C4C2C4
agg_q.195grey.png --------
0: (196,194,196)        #C4C2C4
agg_q.196grey.png --------
0: (196,198,196)        #C4C6C4
agg_q.197grey.png --------
0: (196,198,196)        #C4C6C4
agg_q.198grey.png --------
0: (196,198,196)        #C4C6C4
agg_q.199grey.png --------
0: (196,198,196)        #C4C6C4
agg_q.200grey.png --------
0: (204,202,204)        #CCCACC
agg_q.201grey.png --------
0: (204,202,204)        #CCCACC
agg_q.202grey.png --------
0: (204,202,204)        #CCCACC
agg_q.203grey.png --------
0: (204,202,204)        #CCCACC
agg_q.204grey.png --------
0: (204,206,204)        #CCCECC
agg_q.205grey.png --------
0: (204,206,204)        #CCCECC
agg_q.206grey.png --------
0: (204,206,204)        #CCCECC
agg_q.207grey.png --------
0: (204,206,204)        #CCCECC
agg_q.208grey.png --------
0: (212,210,212)        #D4D2D4
agg_q.209grey.png --------
0: (212,210,212)        #D4D2D4
agg_q.210grey.png --------
0: (212,210,212)        #D4D2D4
agg_q.211grey.png --------
0: (212,210,212)        #D4D2D4
agg_q.212grey.png --------
0: (212,214,212)        #D4D6D4
agg_q.213grey.png --------
0: (212,214,212)        #D4D6D4
agg_q.214grey.png --------
0: (212,214,212)        #D4D6D4
agg_q.215grey.png --------
0: (212,214,212)        #D4D6D4
agg_q.216grey.png --------
0: (220,218,220)        #DCDADC
agg_q.217grey.png --------
0: (220,218,220)        #DCDADC
agg_q.218grey.png --------
0: (220,218,220)        #DCDADC
agg_q.219grey.png --------
0: (220,218,220)        #DCDADC
agg_q.220grey.png --------
0: (220,222,220)        #DCDEDC
agg_q.221grey.png --------
0: (220,222,220)        #DCDEDC
agg_q.222grey.png --------
0: (220,222,220)        #DCDEDC
agg_q.223grey.png --------
0: (220,222,220)        #DCDEDC
agg_q.224grey.png --------
0: (228,226,228)        #E4E2E4
agg_q.225grey.png --------
0: (228,226,228)        #E4E2E4
agg_q.226grey.png --------
0: (228,226,228)        #E4E2E4
agg_q.227grey.png --------
0: (228,226,228)        #E4E2E4
agg_q.228grey.png --------
0: (228,230,228)        #E4E6E4
agg_q.229grey.png --------
0: (228,230,228)        #E4E6E4
agg_q.230grey.png --------
0: (228,230,228)        #E4E6E4
agg_q.231grey.png --------
0: (228,230,228)        #E4E6E4
agg_q.232grey.png --------
0: (236,234,236)        #ECEAEC
agg_q.233grey.png --------
0: (236,234,236)        #ECEAEC
agg_q.234grey.png --------
0: (236,234,236)        #ECEAEC
agg_q.235grey.png --------
0: (236,234,236)        #ECEAEC
agg_q.236grey.png --------
0: (236,238,236)        #ECEEEC
agg_q.237grey.png --------
0: (236,238,236)        #ECEEEC
agg_q.238grey.png --------
0: (236,238,236)        #ECEEEC
agg_q.239grey.png --------
0: (236,238,236)        #ECEEEC
agg_q.240grey.png --------
0: (244,242,244)        #F4F2F4
agg_q.241grey.png --------
0: (244,242,244)        #F4F2F4
agg_q.242grey.png --------
0: (244,242,244)        #F4F2F4
agg_q.243grey.png --------
0: (244,242,244)        #F4F2F4
agg_q.244grey.png --------
0: (244,246,244)        #F4F6F4
agg_q.245grey.png --------
0: (244,246,244)        #F4F6F4
agg_q.246grey.png --------
0: (244,246,244)        #F4F6F4
agg_q.247grey.png --------
0: (244,246,244)        #F4F6F4
agg_q.248grey.png --------
0: (252,250,252)        #FCFAFC
agg_q.249grey.png --------
0: (252,250,252)        #FCFAFC
agg_q.250grey.png --------
0: (252,250,252)        #FCFAFC
agg_q.251grey.png --------
0: (252,250,252)        #FCFAFC
agg_q.252grey.png --------
0: (252,254,252)        #FCFEFC
agg_q.253grey.png --------
0: (252,254,252)        #FCFEFC
agg_q.254grey.png --------
0: (252,254,252)        #FCFEFC
agg_q.255grey.png --------
0: (252,254,252)        #FCFEFC
[rich at peyote bg 12:32:02]$ 

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