render map image in png8

[nick_xu]

Hi,

we are using MGE 2010.

In order to reduce image size we changed
OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG to OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG8,

Image size reduced from 500k to 100k, but the image quality is bad. So we changed OPERATION=GETMAPIMAGE&FORMAT=PNG8 and the image quality is good enough(image size 100k).

please see attached imge

png_getMapImage: OPERATION=GETMAPIMAGE&FORMAT=PNG8
png: OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG
png8: OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG8.

GETDYNAMICMAPOVERLAYIMAGE operation has more parameter to use and can render selection sepeartely. Beside this one,is any difference as these two operation rendering image?

thanks!

Nick

[dswilson]

I don't believe GETDYNAMICOVERLAY processes base layers for tiled maps, hence the name. GetMapImage will process both.

Dave

[nick_xu]

We didn't use tiled maps.

We changed the function
function RequestMapImage(reqId, viewParams)

from
//url = webAgent + "?OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG8&VERSION=2.1.0&SESSION=" + sessionId + "&MAPNAME=" + encodeComponent(mapName) + "&SEQ=" + Math.random() + "&CLIENTAGENT=" + encodeComponent(clientAgent) + "&BEHAVIOR=2";

to
url = webAgent + "?OPERATION=GETMAPIMAGE&FORMAT=PNG8&VERSION=2.1.0&SESSION=" + sessionId + "&MAPNAME=" + encodeComponent(mapName) + "&SEQ=" + Math.random() + "&CLIENTAGENT=" + encodeComponent(clientAgent) + "&BEHAVIOR=2";

}

the getMapImage operation gets image much better that getDynamciMapOverLayImager in png8 fromat(same size).
also, we try the image format in jpeg.

why?

nick