Merge pull request #89 from swarm-lab/develop

Add approxPolyDP.

NAMESPACE

@@ -80,6 +80,7 @@ export(add)
 export(addWeighted)
 export(anisotropicDiffusion)
 export(api)
+export(approxPolyDP)
 export(arcLength)
 export(autothreshold)
 export(bilateralFilter)

R/feature.R

@@ -255,7 +255,7 @@ goodFeaturesToTrack <- function(image, max_corners, quality_level, min_distance,
     if (!all(mask$dim()[1:2] == image$dim()[1:2]))
       stop("mask does not have the same dimensions as image.")
 
-    if (mask$depth() != 1)
+    if (mask$depth() != "8U")
       stop("mask is not an 8U 'Image' object.")
   }
 

R/shape.R

@@ -881,6 +881,57 @@ arcLength <- function(curve, closed = TRUE) {
 }
 
 
+#' @title Calculate a Contour Perimeter or a Curve Length
+#'
+#' @description \code{approxPolyDP} approximates a curve or a polygon with
+#'  another curve/polygon with less vertices so that the distance between them
+#'  is less or equal to the specified precision. It uses the Douglas-Peucker
+#'  algorithm.
+#'
+#' @param curve An m x 2 matrix of 2D coordinates.
+#'
+#' @param epsilon A numeric specifying the approximation accuracy. This is the
+#'  maximum distance between the original curve and its approximation.
+#'
+#' @param closed A logical indicating whether the curve is closed (perimeter) or
+#'  not (default: TRUE).
+#'
+#' @return A matrix with two columns:
+#'  \itemize{
+#'    \item{"x": }{the x coordinates of the approximated curve.}
+#'    \item{"y": }{the y coordinates of the approximated curve.}
+#'  }
+#'
+#' @author Simon Garnier, \email{garnier@@njit.edu}
+#'
+#' @seealso \code{\link{findContours}}
+#'
+#' @references Douglas, D. H., & Peucker, T. K. (1973). ALGORITHMS FOR THE
+#'  REDUCTION OF THE NUMBER OF POINTS REQUIRED TO REPRESENT A DIGITIZED LINE OR
+#'  ITS CARICATURE. Cartographica: The International Journal for Geographic
+#'  Information and Geovisualization, 10(2), 112–122.
+#'  doi:10.3138/FM57-6770-U75U-7727
+#'
+#' @examples
+#' dots <- image(system.file("sample_img/dots.jpg", package = "Rvision"))
+#' dots_gray <- changeColorSpace(dots, "GRAY")
+#' dots_bin <- dots_gray < 200
+#' contours <- findContours(dots_bin)
+#' ix <- contours$contours[, 1] == 0
+#' approxPolyDP(contours$contours[ix, 2:3], 10)
+#'
+#' @export
+approxPolyDP <- function(curve, epsilon, closed = TRUE) {
+  if (!is.matrix(curve))
+    stop("curve must be a m x 2 matrix.")
+
+  if (ncol(curve) != 2)
+    stop("curve must be a m x 2 matrix.")
+
+  `_approxPolyDP`(curve, epsilon, closed)
+}
+
+
 #' @title Pixel Values Along a Line Segment
 #'
 #' @description \code{improfile} finds all pixels intersected by a line segment

docs/pkgdown.yml

@@ -9,7 +9,7 @@ articles:
   z5_gpu: z5_gpu.html
   z6_queue: z6_queue.html
   z7_stack: z7_stack.html
-last_built: 2023-08-04T10:50Z
+last_built: 2023-08-08T12:51Z
 urls:
   reference: https://swarm-lab.github.io/Rvision/reference
   article: https://swarm-lab.github.io/Rvision/articles

docs/sitemap.xml

@@ -84,6 +84,9 @@
   <url>
     <loc>https://swarm-lab.github.io/Rvision/reference/api.html</loc>
   </url>
+  <url>
+    <loc>https://swarm-lab.github.io/Rvision/reference/approxPolyDP.html</loc>
+  </url>
   <url>
     <loc>https://swarm-lab.github.io/Rvision/reference/arcLength.html</loc>
   </url>

src/shape.h

@@ -354,14 +354,35 @@ Rcpp::List _minAreaRect(arma::Mat< float > points) {
 }
 
 double _arcLength(Rcpp::NumericMatrix curve, bool closed) {
-  std::vector< cv::Point > contourpoints(curve.nrow());
+  std::vector< cv::Point > curvepoints(curve.nrow());
 
   for (int i = 0; i < curve.nrow(); i++) {
-    contourpoints[i].x = curve(i, 0);
-    contourpoints[i].y = curve(i, 1);
+    curvepoints[i].x = curve(i, 0);
+    curvepoints[i].y = curve(i, 1);
   }
 
-  return cv::arcLength(contourpoints, closed);
+  return cv::arcLength(curvepoints, closed);
+}
+
+Rcpp::NumericMatrix _approxPolyDP(Rcpp::NumericMatrix curve, double epsilon, bool closed) {
+  std::vector< cv::Point > curvepoints(curve.nrow());
+  std::vector< cv::Point > approxpoints;
+
+  for (int i = 0; i < curve.nrow(); i++) {
+    curvepoints[i].x = curve(i, 0);
+    curvepoints[i].y = curve(i, 1);
+  }
+
+  cv::approxPolyDP(curvepoints, approxpoints, epsilon, closed);
+  Rcpp::NumericMatrix out(approxpoints.size(), 2);
+  colnames(out) = Rcpp::CharacterVector::create("x", "y");
+
+  for (int i = 0; i < approxpoints.size(); i++) {
+    out(i, 0) = approxpoints[i].x;
+    out(i, 1) = approxpoints[i].y;
+  }
+
+  return out;
 }
 
 Rcpp::NumericMatrix _pline(Image& image, Rcpp::NumericVector xi,

src/visionModule.cpp

@@ -358,6 +358,7 @@ RCPP_MODULE(methods_Shape) {
            _["image2"], _["method"]), "");
   function("_minAreaRect", &_minAreaRect, List::create(_["points"]), "");
   function("_arcLength", &_arcLength, List::create(_["curve"], _["closed"]), "");
+  function("_approxPolyDP", &_approxPolyDP, List::create(_["curve"], _["epsilon"], _["closed"]), "");
   function("_pline", &_pline, List::create(_["image"], _["xi"], _["yi"],
            _["connectivity"], _["leftToRight"]), "");
 }