[mapserver-users] MS 6.0 beta6 and faulty image/png; mode=8bit output if source image has overviews

[Erik Gustafson]

On Tue, Apr 19, 2011 at 10:27 AM, thomas bonfort
<thomas.bonfort at gmail.com> wrote:
> Erik,
> the png compression that is applied is now configurable, and defaults
> to "6". You can set it as it was by default in 5.6 for quantized
> output with
> FORMATOPTION "COMPRESSION=9"
>
> please post your image size after the change.
>

Mapserver 5.6: 74kb
Mapserver 6, compression 1: 133kb
Mapserver 6, compression 9: 129kb

I'm on deep water now because I do not know much about the png-format.
But, by looking at the output from gdalinfo the image from mapserver 5
seems to have most colors set to rgba 255,255,255,255


rio% gdalinfo out_v5.png|sed '1,/Color Table/d'|head -20
    0: 255,255,255,255
    1: 8,139,121,255
    2: 255,255,255,255
    3: 255,255,255,255
    4: 5,202,56,255
    5: 140,199,90,255
    6: 255,255,255,255
    7: 81,201,28,255
    8: 207,135,90,255
    9: 255,255,255,255
   10: 255,255,255,255
   11: 255,255,255,255
   12: 140,138,170,255
   13: 255,255,255,255
   14: 95,95,132,255
   15: 255,255,255,255
   16: 255,255,255,255
   17: 255,255,255,255
   18: 255,255,255,255
   19: 255,255,255,255
rio% gdalinfo out_compression9_v6.png|sed '1,/Color Table/d'|head -20
    0: 22,253,20,255
    1: 6,253,6,255
    2: 0,249,0,255
    3: 6,253,10,255
    4: 0,253,4,255
    5: 16,253,18,255
    6: 20,20,255,255
    7: 6,253,8,255
    8: 80,80,255,255
    9: 96,94,253,255
   10: 102,102,255,255
   11: 0,239,16,255
   12: 74,76,255,255
   13: 64,64,255,255
   14: 8,249,16,255
   15: 161,255,161,255
   16: 34,253,36,255
   17: 26,26,255,255
   18: 0,235,18,255
   19: 0,245,10,255

 /Erik