Global Mapper v25.0

Contrast adjustment on multiple images

HenryM
HenryM Global Mapper User
edited December 2008 in Raster Data
I have a set of DOQQ images that, over all images, are well color/contrast balanced but print too dark. Simple batch convert contrast adjustment doesn't fix the contrast like Linear Stretch at 4 SD. Is there a way to load all the files, use GM to adjust contrast over all the images (Linear Stretch at 4 SD over all loaded data), then Export the results to individual files with the same input filenames (or with a pre-prepended character) to a different sub-directory?

Loading, contrast adjusting, and Exporting with a grid and digitizer tool won't work because the file naming is not preserved. Individually processing the images results in unacceptable tiling with different visual appearance.

The idea is to have the contrast adjustment made globally and then have the results written back out with the same extents and filenames as the individual input files. All the files are GeoTIFF format.

Comments

  • global_mapper
    global_mapper Administrator
    edited December 2008
    I have updated the batch conversion to use the auto-contrast settings from a loaded copy of the file being converted if auto-contrast is enabled for the batch conversion. So you should now be able to load up all of your files and do the shared auto-contrast adjustment as you want, then start a batch conversion and just add the loaded files, then get the results that you want. I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the change for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • HenryM
    HenryM Global Mapper User
    edited December 2008
    Thanks, Mike. As always just right and fast as lightning. No more obvious tiling just seamless images for viewing and printing. BTW, what is the limit of loading raster images? I presume memory plus HD space.

    Henry
  • global_mapper
    global_mapper Administrator
    edited December 2008
    Henry,

    There is not any hard limit for loading images. Each one will take some memory, but in most cases they are read from disk as needed. You can also use map catalogs to allow even larger collections to be efficiently managed.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com