We have recently received orthoimagery tiles for my county. The county is a series of islands and the imagery only covers the islands. Thus we have data gaps where there is only water. In past projects we've created a mosaic by filling in the gaps using a solid blue color that somewhat resembles the median color of the water in the tiles near the shorelines. It worked pretty well in the past, but with this project I'm finding that no single color is working best. Is there a method I can use to make the transition from imagery edge to a solid color more aesthetically pleasing?
As BradHards noted, "pleasing" is subjective. That being said, two methods come to mind:
(1) Create a new constant raster, erase the islands (assuming you have a vector layer for their boundaries (if not, create one)), and calculate euclidean distance away from the island shores. ESRI has a white paper outlining this method here, although the general idea would work in any GIS program: http://support.esri.com/en/knowledgebase/whitepapers/view/productid/39/metaid/975
(2) Add a vector ocean mask and erase an area (as above) where each island lies. Then, export a high resolution map to Photoshop or a graphics program of your choice. Use the clone tool to copy the near-shore water and work outwards from there. Gradually fading to the solid vector layer.