Didger imports ERMapper .ECW files.
Enhanced Compression Wavelet .ECW is an open standard wavelet compression image format developed by Earth Resource Mapping. The file format is optimized for aerial and satellite imagery, and efficiently compresses very large images with fine, alternating contrast. This is a lossy compression format.
The .ECW file format has the following properties:
Embeds map projection information
Fast compression (about 1.5 MB of compressed file per second on 1 GHz processor)
Typical compression ratios between 1:10 and 1:100
Possible decompression of selected regions without the need to decompress the whole file
Data flow compression allows for compression of big files with small RAM requirements
Import Options
See .ECW Image Import Options Dialog.
Export Options
Didger does not currently export this file format.
Remarks
When loading a very large .ECW file, it may load with poor resolution. To save on loading and processing time, it was necessary to design Didger to automatically reduce the resolution of very large .ECW files, even when choosing a Pixel Reduction of 1/1 during import. If the .ECW file is larger than 8192 x 8192 pixels, then Didger will automatically scale it down by halving the number of pixels until the largest dimension is under 8192 pixels.
For example, your .ECW file is 28000 x 14000 pixels. Divide that in half to get 14000 x 7000 pixels. Since the largest dimension is still over 8192 pixels, divide it again to get the pixel dimensions of 7000 x 3500 pixels (with a Pixel Reduction of 1/1).
There is currently not a way to change this. If you would like to add your vote for more user control over the maximum pixel dimensions when importing .ECW files, please email Didgersupport@goldensoftware.com.
See Also