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BoofCV is an open source Java library for real-time computer vision and robotics applications.
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/*
* Copyright (c) 2020, Peter Abeles. All Rights Reserved.
*
* This file is part of BoofCV (http://boofcv.org).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package boofcv.misc;
import georegression.struct.point.Point2D_I32;
import org.ddogleg.struct.DogArray;
/**
* Functions related to discretized circles for image processing
*
* @author Peter Abeles
*/
public class DiscretizedCircle {
/**
* Computes the offsets for a discretized circle of the specified radius for an
* image with the specified width.
*
* @param radius The radius of the circle in pixels.
* @param imgWidth The row step of the image
* @return A list of offsets that describe the circle
*/
public static int[] imageOffsets(double radius, int imgWidth) {
double PI2 = Math.PI * 2.0;
double circumference = PI2 * radius;
int num = (int) Math.ceil(circumference);
num = num - num % 4;
double angleStep = PI2 / num;
int temp[] = new int[(int) Math.ceil(circumference)];
int i = 0;
int prev = 0;
for (double ang = 0; ang < PI2; ang += angleStep) {
int x = (int) Math.round(Math.cos(ang) * radius);
int y = (int) Math.round(Math.sin(ang) * radius);
int pixel = y * imgWidth + x;
if (pixel != prev) {
// System.out.println("i = "+i+" x = "+x+" y = "+y);
temp[i++] = pixel;
}
prev = pixel;
}
if (i == temp.length)
return temp;
else {
int ret[] = new int[i];
System.arraycopy(temp, 0, ret, 0, i);
return ret;
}
}
public static void coordinates(double radius, DogArray coordinates ) {
coordinates.reset();
double PI2 = Math.PI * 2.0;
double circumference = PI2 * radius;
int num = (int) Math.ceil(circumference);
num = num - num % 4;
double angleStep = PI2 / num;
int width = (int)Math.ceil(radius)*2+1;
int prev = 0;
for (double ang = 0; ang < PI2; ang += angleStep) {
int x = (int) Math.round(Math.cos(ang) * radius);
int y = (int) Math.round(Math.sin(ang) * radius);
int pixel = y * width + x;
if (pixel != prev) {
coordinates.grow().setTo(x,y);
}
prev = pixel;
}
}
public static int[][] imageOffsets2(double radius) {
double PI2 = Math.PI * 2.0;
double circumference = PI2 * radius;
int num = (int) Math.ceil(circumference);
num = num - num % 4;
double angleStep = PI2 / num;
int temp[][] = new int[num][2];
for (int i = 0; i < num; i++) {
double ang = angleStep * i;
int x = (int) Math.round(Math.cos(ang) * radius);
int y = (int) Math.round(Math.sin(ang) * radius);
temp[i][0] = x;
temp[i][1] = y;
// System.out.println("i = "+i+" x = "+x+" y = "+y);
}
return temp;
}
}
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