selectUniform

Select uniformly distributed subset of feature points

Syntax

pointsOut = selectUniform(points,N,imageSize)

Description

pointsOut = selectUniform(points,N,imageSize) returns N uniformly distributed points from pointsIn points of an image of size imageSize.

Examples

Select Uniformly Distributed Subset of KAZE Features

Read an image.

im = imread("yellowstone_left.png");

Detect and display KAZE features.

points1 = detectKAZEFeatures(im2gray(im))

points1 = 
  6712x1 KAZEPoints array with properties:

       Location: [6712x2 single]
         Metric: [6712x1 single]
          Count: 6712
          Scale: [6712x1 single]
    Orientation: [6712x1 single]

subplot(1,2,1)
imshow(im)
hold on
plot(points1)
hold off
title("Original Points")

Select a uniformly distributed subset of points.

numPoints = 100;
points2 = selectUniform(points1,numPoints,size(im))

points2 = 
  100x1 KAZEPoints array with properties:

       Location: [100x2 single]
         Metric: [100x1 single]
          Count: 100
          Scale: [100x1 single]
    Orientation: [100x1 single]

subplot(1,2,2)
imshow(im)
hold on
plot(points2)
hold off
title("Uniformly Distributed Points")

Select Uniformly Distributed Subset of Harris Features From Image

Load an image.

im = imread("yellowstone_left.png");

Detect many corners by reducing the quality threshold.

points1 = detectHarrisFeatures(im2gray(im),MinQuality=0.05);

Plot image with detected corners.

subplot(1,2,1);
imshow(im);
hold on
plot(points1);
hold off
title("Original points");

Select a uniformly distributed subset of points.

numPoints = 100;
points2 = selectUniform(points1,numPoints,size(im));

Plot images showing original and subset of points.

subplot(1, 2, 2);
imshow(im);
hold on
plot(points2);
hold off
title("Uniformly distributed points");

Select A Uniformly Distributed Subset of BRISK Features From Image

Load an image into the workspace.

im = imread("yellowstone_left.png");

Detect many corners by reducing the quality threshold.

points1 = detectBRISKFeatures(im2gray(im),MinQuality=0.05);

Plot image with detected corners.

subplot(1,2,1);
imshow(im);
hold on
plot(points1);
hold off
title("Original points");

Select a uniformly distributed subset of points.

numPoints = 100;
points2 = selectUniform(points1,numPoints,size(im));

Plot images showing original and subset of points.

subplot(1, 2, 2);
imshow(im);
hold on
plot(points2);
hold off
title("Uniformly distributed points");

Select Uniformly Distributed Subset of SURF Features from an Image

Load an image.

im = imread("yellowstone_left.png");

Detect and display SURF features.

points1 = detectSURFFeatures(im2gray(im));
subplot(1,2,1);
imshow(im);
hold on
plot(points1);
hold off
title("Original points");

Select a uniformly distributed subset of points.

numPoints = 100;
points2 = selectUniform(points1,numPoints,size(im));

Plot images showing original and subset of points.

subplot(1, 2, 2);
imshow(im);
hold on
plot(points2);
hold off
title("Uniformly distributed points");

Input Arguments

points — Points object

M-by-2 matrix | point feature object

Points object,specified as an M-by-2 matrix of M number of [x y] coordinates, or as one of the point feature objects described in Point Feature Types. The object contains information about the feature points detected in the input image. To obtain points, use the appropriate detect function that pairs with the point feature type.

N — Number of points

integer

Number of uniformly distributed points to select, specified as an integer.

imageSize — Size of image

2-element vector | 3-element vector

Size of image, specified as a 2-element vector for grayscale images or a 3-element vector for truecolor images.

Version History

Introduced in R2012a