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Specifying a Compression Ratio

Specify a compression ratio for an image to specify how much smaller you want an image to be than the input image. For example, if you have a 100 megabyte image and you specify a compression ratio of 20:1, the file size of the output image is 5 megabytes.

NOTE: For previously-compressed data, the compression ratio is relative to the nominal size, not the input file size. Specifying a 10:1 compression ratio for a file that was already compressed 20:1 will likely yield a much larger file.

1. Click the Add Image icon to add an image to the Job List.
2. Select the image in the Job List.
3. In the Properties tab, select the radio button next to the blank compression ratio field. Then, enter the compression ratio that you want to use.
4. Enter the ratio that you want to use in the text field.

As a rule of thumb, you can compress raster images to a ratio of 20:1 without introducing noticeable compression artifacts. Compression artifacts include blurring and speckling. By default, the compression ratio for RGB images is 20:1 and the compression ratio for grayscale images is 10:1. For multispectral images and LiDAR point clouds, GeoExpress uses lossless compression by default.