tiff size

[Stephen Lime]

MapServer can easily display TIFs 15K on a side. The image is sampled using nearest neighbor which is all that makes sense for colormapped data. The effects of this sampling vary greatly from image to image. For example, DRGs pretty much suck at all but a couple of sampling intervals. This is because they are more like line art and lines (eg. roads and contours) can easily disapear and reappear. Conversely, continuous data like doqs, landsat images or wall-to-wall classifications look fine. I posted a url a week or so ago for a DRG viewer and the only way I could get it to work was to scrap infinite zooms in favor of specific displays at scales that I know the image will look good. With 8-bit output this is just the way things work no matter what package your using. 24 -bit output allows for cubic-convolution or bilinear interpolation resampling which will greatly enhance certain types of image viewing- at a cost though- speed. I personally have used image files larger than 300 Mb with no problems. Send a sample if this doesn't answer your question.

Steve

<<< Michael Hass <mdh20 at axe.humboldt.edu> 12/30  3:38p >>>

Is there a limit to the size of a tiff that can be effectively
displayed? I've tried to display a tiff that is 26meg's and then 
a smaller one that was 4meg's and I am either getting a pixel here
a pixel there (like it blew up) or its greying out half way (this is
running the java/javascript version).

The map file is written in the same manner as the demo, the tif has
a wld file that works, etc. I'm wondering if I need to degrade the image
to below a meg to get effective results.

Thanks
Mike Hass
HSU