LizardTech image metadata is information about the pixel values that tells viewing software how to interpret or treat each pixel. There are many image metadata tags, and a small subset of these are available for editing.
Editing the image tags does not affect the pixel values themselves. For example, changing WKT metadata does not reproject an image from one CRS to another. However, changing metadata may affect how an image is displayed in a viewer.
You can assign a WKT to the image that identifies its coordinate reference system. This is useful when you know the CRS of an image but that data isn't captured anywhere in the file. It's also useful if the WKT is incorrect and you need to correct it.
Setting the WKT in the metadata of an image does NOT reproject the image. It only identifies where the image already is. To reproject an image to a new CRS, use the reprojection tools. Additionally, carelessly changing the WKT of an image may make the image inaccurate or unusable in any GIS applications that rely on this information.
These X and Y fields can be used to set the x,y location of the image.
These X and Y fields can be used to set the x and y resolutions of the image.
To improve the appearance of MrSID images in other GIS programs, you can use GeoExpress to write dynamic range metadata for images.
NOTE: If you select MrSID Generation 4 as the image output format, dynamic range values are calculated automatically for all images except for eight bit images. If you want to enter the dynamic range values manually for those images, change the method for generating the dynamic range to None in the Format-Specific tab of the Advanced Job Options dialog. For more information on calculating the dynamic range, see Dynamic Range Metadata Generation.
The dynamic range metadata is particularly useful for images that only use a small portion of their datatype bandwidth. For example, 11-bit images are often stored as 16-bit images, where the upper five bits are left empty. The only bits that are meaningful are the first eleven. The full dynamic range of pixel values in an unsigned 16-bit image runs from 0 to 65535. The first eleven bits fall between 0 and 2047, which is only 3% of the full range! When you look at the histogram of this image (for information on histograms see The Color Balance Tool), all of the values will be gathered into the far left side, causing the image to appear black when it's scaled to display on a computer monitor. For an 11-bit image, the minimum value would be 0 and the maximum value would be 2047 (211 - 1).
An alternate way to think of dynamic range is "window and level." The window is the width of data that's important and the level is where the midpoint of the window lies within the entire range. For our 11-bit image, the window, or width, is 2048 (211), and the level, or midpoint, is 1023.5 ((211 -1 ) / 2). The window and level are displayed next to the Min and Max fields to aid you in setting the dynamic range.
To set the dynamic range of the image, type the minimum pixel value in the Min field and the maximum pixel value in the Max field.
Setting the dynamic range does not change the pixel data of the image. It only gives clues as to how the image should be displayed. Some applications may honor this value and some may ignore it, depending on how the pixels need to be represented for a given workflow. Additionally, setting the dynamic range is not the same as color balancing. Color balancing changes the actual pixel values, which changes the nature of the image. (For more information see Performing Color Balancing for a Mosaic.)