uas_cropctr: Crop out the center of images

In UCANR-IGIS/uasimg: Drone Image Utilities

Crop out the center of images

Description

Crop out the center of images

Usage

uas_cropctr(
  x,
  crp_h = 10,
  crp_w = 10,
  dir_out = ".",
  out_prefix = "",
  out_suffix = "_crp",
  overwrite = FALSE,
  quiet = FALSE
)

Arguments

x	A list of class 'uas_info'
crp_h	Height of the crop box (meters)
crp_w	Width of the crop box (meters)
dir_out	The output directory for the cropped images
out_prefix	A character object that will be pre-pended to output file names
out_suffix	A character object that will be suffixed to output file names (before the extension)
overwrite	Overwrite existing files, T/F
quiet	Suppress messages and printing of the pandoc command line, T/F

Details

This function will crop around the center of a set of images. This can be used to create a photomosaic. If the photos were taken at nadir (i.e., straight down), the center region of each photo is often the least distorted. If the images have world files created for them (see uas_worldfile), the cropped images will have the world files also. If the images have been cropped to minimize the amount of overlap between then, and they have world files, viewing them in GIS software should results in a basic photo mosaic (albeit without any stitching or blending).

This function requires the command line version of gdal to be installed. For instructions see http://gdal.org. Windows users can download a gdal installation file (*.msi) from http://www.gisinternals.com/release.php, install the software, add the installation directory to the system path (using the Windows Control Panel >> System >> Advanced), and restart RStudio. To see if it worked, run Sys.which("gdal_translate").

If the images were collected in a grid pattern, you can use the average distance between centers as the value for 'crp_h', and the average distance between flight lines for 'crp_w'. This will result in cropped images where the edges are just touching. 'crp_h' and 'crp_w' should be expressed in meters.

Value

A vector of the image files created

See Also

uas_worldfile

UCANR-IGIS/uasimg documentation built on Jan. 16, 2025, 10:29 p.m.