invariant_hash: invariant hashing (caclulation of the hamming or the levenshtein distance when the image is flipped, rotated or cropped)

Description

flip-rotate-crop an image and caclulate the hamming or the levenshtein distance for phash, average_hash, dhash

Usage

invariant_hash(
  image,
  new_image,
  method = "phash",
  mode = "binary",
  hash_size = 8,
  highfreq_factor = 4,
  resize = "nearest",
  flip = T,
  rotate = T,
  angle_bidirectional = 10,
  crop = T
)

Value

If flip, rotate and crop are all FALSE then the function returns either the hamming distance (if mode = 'binary') or the levenshtein distance (if mode = 'hash') for the two images. If any of the flip, rotate, crop is TRUE then it returns the MIN, MAX of the hamming distance (if mode = 'binary') or the MIN,MAX of the levenshtein distance (if mode = 'hash').

Arguments

image: a 2-dimensional matrix or data frame (only gray-scale images are valid)
new_image: a new image to be compared with the previous input image
method: one of 'phash', 'average_hash', 'dhash'
mode: one of 'binary', 'hash'
hash_size: an integer specifying the hash size. IF method = 'phash' : the hash_size * highfreq_factor should be less than number of floor(rows * 0.8) or floor(columns * 0.8) of the gray_image IF method = 'dhash' or 'average_hash' : the hash_size should be less than number of floor(rows * 0.8) or floor(columns * 0.8) of the gray_image
highfreq_factor: an integer specyfing the highfrequency factor (IF method = 'phash' : the hash_size * highfreq_factor should be less than number of floor(rows * 0.8) or floor(columns * 0.8) of the gray_image)
resize: corresponds to one of 'nearest', 'bilinear' (resizing method)
flip: if TRUE the new_image will be flipped both horizontal and vertical
rotate: if TRUE the new_image will be rotated for a specified angle (see angle_bidirectional)
angle_bidirectional: a float specifying the angle that the images should be rotated in both directions. For instance, if angle_bidirectional = 10 then the image will be rotated for 10 and 350 (360-10) degrees.
crop: if TRUE the new_image will be cropped 10 or 20 percent (equally spaced horizontally and vertically)

Details

This function performs the following transformations : flips an image (no-flip, horizonal-flip, vertical-flip), rotates an image (no-angle, angle_bidirectional, 360-angle_bidirectional) and crops an image (no-crop, 10-percent-crop, 20-percent-crop). Depending on the type of mode ('binary', 'hash'), after each transformation the hamming or the levenshtein distance between the two images is calculated.

Examples

Run this code


if (FALSE) {

path1 = system.file("tmp_images", "1.png", package = "OpenImageR")

path2 = system.file("tmp_images", "2.jpg", package = "OpenImageR")

image1 = rgb_2gray(readImage(path1))

image2 = rgb_2gray(readImage(path2))

res1 = invariant_hash(image1, image2, hash_size = 3, flip = TRUE, crop = FALSE)

res2 = invariant_hash(image1, image2, mode = 'hash', hash_size = 3, angle_bidirectional = 10)
}