Function to subset raw images/matrices.
magcutout(image, loc = dim(image)/2, box = c(100, 100), shiftloc = FALSE, paddim = TRUE,
padval = NA, plot = FALSE, ...)A list containing:
Numeric matrix; the cutout region of interst centred around loc.
The new loc vector that tranforms the input loc x and y location to the new cutim coordinates. This is in ProFit coordinates, so these values can be used when, e.g., constructing a ProFit modellist structure.
The original location is provided by the input loc.
The x and y offsets of the cutout compared to the original image, where loc + loc.diff = loc.orig exactly.
Integer vector; the extracted x pixels from the original image that form cutim.
Integer vector; the extracted y pixels from the original image that form cutim.
Numeric matrix; required, the image we want to cutout. If image is a path to an fst format file then the cutout can be done on disk directly.
Numeric vector; the [x,y] location where we want to cutout the image.
Numeric vector; the dimensions of the box to cut out from image centred on loc. For magcutout the box unit is always pixels.
Logical; should the cutout centre shift from loc away from the image edge if the desired box size extends beyond the edge of the image?
Logical; should the cutout dimensions be padded with with value of padval for data outside the image boundary (TRUE)? If FALSE the dimensions will truncate when the edge of the input image has been reached.
Numeric scalar; the value to use for padding if paddim=TRUE.
Logical; should a magimage plot of the output be generated?
Dots are parsed to magimage.
Aaron Robotham & Dan Taranu
This function is on a level trivial, since it is easy to subset matrices and therefore images within R. However magcutout tracks important properties of the subset region that makes it easy to track its location with respect to the original matrix/image. Also, it allows direct plotting of the resultant cutout with the most appropriate image functions. In many cases these functions will be used purely for their plotting side effects.
The shiftloc and paddim control the behaviour of the function in the non-trivial case when the desired box size extendeds beyond the edge of the image. If shiftloc is FALSE (the default behaviour), the cutout is guaranteed to be centred on the pixel specified by loc. Then, if paddim is FALSE, the cutout extends only as far as possible until it reaches the edge of the image; otherwise if paddim is TRUE the cutout image is padded with NAs in regions outside the supplied image (the default behaviour). If shiftloc is TRUE, the centre of the cutout will be shifted. In this case, if paddim is FALSE, the cutout will extend at most half of the supplied box size from the given loc; otherwise if paddim is TRUE the cutout will be expanded until it reaches the desired box size or spans the entire image.
Note that if shiftloc is TRUE and paddim is FALSE, the cutout can be larger than box; otherwise, the cutout is guaranteed to be no larger than the specified box size.
temp=matrix(1:121,11)
#The central value is at:
temp[6,6]
print(magcutout(temp, dim(temp)/2, box=c(3,3))$image)
#Given we cutout around the centre of the central pixel [5.5,5.5], the new centre
#relative to the cutout image output should be at [1.5,1.5]:
print(magcutout(temp, dim(temp)/2, box=c(3,3))$loc.orig)
print(magcutout(temp, dim(temp)/2, box=c(3,3))$loc)
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