Tips for choosing a cache image format

re: Tips for choosing a cache image format

Scott — Mon, 20 Oct 2008 14:42:07 GMT

Is there any way to tell how many colors your map service has?

re: Tips for choosing a cache image format

Carol Fackler — Tue, 21 Oct 2008 23:03:06 GMT

We have a 9.2 cached basemap at 1024 x 1024 in PNG24. It looked good and performed OK in 9.2. We do not need to support transparency because it is a basemap. We have a 9.3 test server. I pointed a new duplicated 9.3 map service to the 9.2 cache using a UNC with a shared directory. I was told you could use a 9.2 cache in a 9.3 map service. Originally I had issues because I tried to create the map service on the 9.3 server using a 9.2 desktop ArcCatalog (I still have other 9.2 servers to support). I found that the cfg files are different in 9.3 and 9.2. The REST services and directory did not work. After re-creating the service in 9.3 it looked like everything was OK until someone noticed that the background was transparent. The background is not transparent in the cached PNG images but it is transparent when you preview the map service or the web application. I looked in the cfg and the IsCached tag was set to false. I set it to true and restarted the SOM's service but the background is still transparent. Any ideas what to do other than rebuild the cache fresh in 9.3?

re: Tips for choosing a cache image format

sterlingdq — Tue, 21 Oct 2008 23:55:35 GMT

@Carol- A 9.3 map service is designed to be compatible with a cache that was built at 9.2. Not sure what is causing the transparency problem you're seeing- it's probably more about how the 9.3 client is interpreting the image. What client are you using that causes different appearance in 9.2 vs. 9.3? Can you explain in more detail "the background is not transparent in the cached PNG images but it is transparent when you preview the map service or the web application."?

Sterling

re: Tips for choosing a cache image format

SBLGIS38 — Wed, 12 Nov 2008 09:16:52 GMT

Informative post.thanks for sharing

regards

<a href="http://www.sblgis.com/gis-lidar.aspx">Lidar mapping services</a>

re: Tips for choosing a cache image format

Jeff1910 — Thu, 13 Nov 2008 17:28:49 GMT

Hello, I would like to make a map web site with Cache. I own 4 ArcGIS Servers Licenses I would like to perform the following: As a user asks a map, he gets the tiles from the four Arcgis Servers (Grid working system) so the user gets the map from four servers and not from one. This method better then working with one server. Is there a way to do it?

re: Tips for choosing a cache image format

sterlingdq — Fri, 14 Nov 2008 17:58:18 GMT

@Jeff- When a user connects to a cached service they typically hit the SOC briefly and from then on they get the tiles directly out of the cache directory. In most cases it's sufficient to have one configuration of your service and one cache directory.

A very large deployment (like ArcGIS Online) might have the cache duplicated on several servers, but this is partly to facilitate failover and update workflows. Unless you have thousands of users depending on your cache night and day, it's probably not worth the trouble.

re: Tips for choosing a cache image format

trangdt — Thu, 05 Feb 2009 08:59:27 GMT

I using ArcGis Server 9.2. Image format caching defalt is .PNG. I would like to create .JPEG for raster image. How do I do? Email: quangletri@gmail.com

re: Tips for choosing a cache image format

sterlingdq — Thu, 05 Feb 2009 17:15:41 GMT

@trangdt - JPEG was added as an option at ArcGIS Server 9.2, Service Pack 1. The additional image formats become available in the caching tools once you apply the service pack.

re: Tips for choosing a cache image format

offermann — Fri, 20 Mar 2009 09:52:52 GMT

@sterlingdq: Regarding JPEG Quality, you wrote "raise the Compression value", where is the right lever to change jpg compression for the ArcGIS Server (9.3)?

btw: is the compression value a server-sided parameter or is there a way to specifiy the value in each request?

Best regards, Stefan

PNG8 tiled layer should be transparent but isn't

Lars — Mon, 27 Apr 2009 22:10:26 GMT

Hi, I'm creating a web map using AGS 9.3 with Javascript API. I have a layer that contains polygons, and it's a tiled cache layer. It's using PNG8. (But it also has antialiasing checked, because that was on by default.) According to the above, the layer should have transparency wherever there are not polygons. And indeed it used to be transparent, with the base map showing through. Now however the base map doesn't show through. I have changed some settings, mainly removing unwanted capabilities, such as KML and Mapping/Data. But I can't figure out why the layer is not transparent.

re: Tips for choosing a cache image format

Lars — Thu, 30 Apr 2009 20:49:18 GMT

My bad. Actually the cached layer *is* transparent. I've been able to verify that the png tiles being served have transparent areas. It's just that the client isn't displaying the base map, for some reason. What actually happens is that whichever layer I add to the map first gets displayed; the one I add second, doesn't. The reverse of what you might expect. I'm puzzled.

re: Tips for choosing a cache image format

sterlingdq — Thu, 30 Apr 2009 22:42:53 GMT

@stefan- The ArcGIS Online team uses a value of 90 for vector-based maps. For raster maps you could probably get away with 75 or lower. The number actually refers to compression quality, so a higher number means less compression. In all cases, build a small test cache and examine the quality to make sure it's right for you.

The compression quality value is only used when creating tiles on the server. It's not a thing that a client can specify on each request.

re: Tips for choosing a cache image format

sterlingdq — Thu, 30 Apr 2009 22:50:46 GMT

@Lars- Do these two maps (base and overlay) use the same tiling scheme? Are the projection and scales common to both services? I can imagine overlay problems if there's a mismatch.

re: Tips for choosing a cache image format

huttarl — Wed, 06 May 2009 18:08:06 GMT

Thanks, Sterling. I think a mismatched tiling scheme is probably the issue. I just watched an online seminar where I learned that the tiling schemes have to match. I'm recreating the cache on our own map service to match the tiling scheme of the arcgis online basemap service. Hopefully that will fix the problem.

Would be great if the AGS Javascript API (and similar) would throw an error or warning if you try to load two cached layers in the same map with different tiling schemes.

re: Tips for choosing a cache image format

Sandip — Tue, 12 May 2009 19:48:14 GMT

Hi, I have a simple (may be stupid!!) question, like if we cache our map data at some specific scales, then what happens if the user zooms in with some scales other than the scales in which the data is cached. Does it try to load the data dynamically?