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Dynamic Range Metadata Generation

To improve the appearance of MrSID images in other GIS programs, use GeoExpress to write dynamic range metadata for images.

You can generate dynamic range metadata for all images with the exception of eight bit images. For an image where the dynamic range is less than the full range of possible values for the image, you can use your GIS program to stretch the pixel values across the full range. For example, if you have a 16-bit image and the dynamic range is 11 bits, then you may want to use dynamic range stretching to improve the appearance of the image.

Dynamic Range Generation Methods

To calculate the dynamic range of an image, select a dynamic range generation method.

You can select one of the following methods for generating the dynamic range:

RGB

Calculate the minimum and maximum dynamic range values for an image with red, green, and blue bands. Select the RGB method to minimize color shifting for RGB images. When you select the rgb method, GeoExpress calculates the combined dynamic range of the red, green, and blue bands.

Merged

Calculate the minimum and maximum dynamic range values for an image with multiple bands. Select the Merged method to preserve the proportions of pixel values across bands. For example, if you want to compare multiple bands in a multispectral image, you may want to select the Merged method. When you select the merge method, GeoExpress calculates the combined dynamic range of all bands.

Per-Band

Calculate the minimum and maximum dynamic range values for an image with one or more bands. Select the Per-Band method to calculate the dynamic range of each band individually. For example, if you have a multispectral image and you only want to view one band at a time, select the Per-Band method. When you select the per-band method, GeoExpress calculates the dynamic range of each band separately.

None

Do not calculate the dynamic range of the image.

NOTE: To enter the minimum and maximum dynamic range values manually, select None as the dynamic range generation method and edit the image metadata. For more information on entering dynamic range metadata manually, see Image Metadata.

Automatic and Strict Dynamic Range

For 16-bit images with unsigned integer data, you can select either Automatic Range or Strict Range. 16-bit images with signed integer data and all 32-bit images use the Strict Range option. The following list describes the two ranges that you can select:

• Automatic Range. Set the maximum value to the estimated bit-depth and set the minimum value to zero. The estimated bit-depth is the next whole number of bits that contains the calculated maximum value in the image. For example, if the maximum value in the image is 3950, GeoExpress estimates that the image was taken with a 12-bit camera and sets the maximum value to 4095. Because GeoExpress sets a wider dynamic range for the image, you can minimize color shifting when you display the image.
• Strict Range. Set the maximum and minimum values to the exact dynamic range values calculated by GeoExpress.