diff --git a/src/main/java/com/thealgorithms/lineclipping/CohenSutherland.java b/src/main/java/com/thealgorithms/lineclipping/CohenSutherland.java new file mode 100644 index 000000000000..6e8611b86332 --- /dev/null +++ b/src/main/java/com/thealgorithms/lineclipping/CohenSutherland.java @@ -0,0 +1,133 @@ +package com.thealgorithms.lineclipping; + +import com.thealgorithms.lineclipping.utils.Line; +import com.thealgorithms.lineclipping.utils.Point; + +/** + * @author shikarisohan + * @since 10/4/24 + * Cohen-Sutherland Line Clipping Algorithm + * + * This algorithm is used to clip a line segment to a rectangular window. + * It assigns a region code to each endpoint of the line segment, and + * then efficiently determines whether the line segment is fully inside, + * fully outside, or partially inside the window. + * + * Reference: + * https://en.wikipedia.org/wiki/Cohen%E2%80%93Sutherland_algorithm + * + * Clipping window boundaries are defined as (xMin, yMin) and (xMax, yMax). + * The algorithm computes the clipped line segment if it's partially or + * fully inside the clipping window. + */ +public class CohenSutherland { + + // Region codes for the 9 regions + private static final int INSIDE = 0; // 0000 + private static final int LEFT = 1; // 0001 + private static final int RIGHT = 2; // 0010 + private static final int BOTTOM = 4; // 0100 + private static final int TOP = 8; // 1000 + + // Define the clipping window + double xMin; + double yMin; + double xMax; + double yMax; + + public CohenSutherland(double xMin, double yMin, double xMax, double yMax) { + this.xMin = xMin; + this.yMin = yMin; + this.xMax = xMax; + this.yMax = yMax; + } + + // Compute the region code for a point (x, y) + private int computeCode(double x, double y) { + int code = INSIDE; + + if (x < xMin) // to the left of rectangle + { + code |= LEFT; + } else if (x > xMax) // to the right of rectangle + { + code |= RIGHT; + } + if (y < yMin) // below the rectangle + { + code |= BOTTOM; + } else if (y > yMax) // above the rectangle + { + code |= TOP; + } + + return code; + } + + // Cohen-Sutherland algorithm to return the clipped line + public Line cohenSutherlandClip(Line line) { + double x1 = line.start.x; + double y1 = line.start.y; + double x2 = line.end.x; + double y2 = line.end.y; + + int code1 = computeCode(x1, y1); + int code2 = computeCode(x2, y2); + boolean accept = false; + + while (true) { + if ((code1 == 0) && (code2 == 0)) { + // Both points are inside the rectangle + accept = true; + break; + } else if ((code1 & code2) != 0) { + // Both points are outside the rectangle in the same region + break; + } else { + // Some segment of the line is inside the rectangle + double x = 0; + double y = 0; + + // Pick an endpoint that is outside the rectangle + int codeOut = (code1 != 0) ? code1 : code2; + + // Find the intersection point using the line equation + if ((codeOut & TOP) != 0) { + // Point is above the rectangle + x = x1 + (x2 - x1) * (yMax - y1) / (y2 - y1); + y = yMax; + } else if ((codeOut & BOTTOM) != 0) { + // Point is below the rectangle + x = x1 + (x2 - x1) * (yMin - y1) / (y2 - y1); + y = yMin; + } else if ((codeOut & RIGHT) != 0) { + // Point is to the right of the rectangle + y = y1 + (y2 - y1) * (xMax - x1) / (x2 - x1); + x = xMax; + } else if ((codeOut & LEFT) != 0) { + // Point is to the left of the rectangle + y = y1 + (y2 - y1) * (xMin - x1) / (x2 - x1); + x = xMin; + } + + // Replace the point outside the rectangle with the intersection point + if (codeOut == code1) { + x1 = x; + y1 = y; + code1 = computeCode(x1, y1); + } else { + x2 = x; + y2 = y; + code2 = computeCode(x2, y2); + } + } + } + + if (accept) { + return new Line(new Point(x1, y1), new Point(x2, y2)); + } else { + + return null; // The line is fully rejected + } + } +} diff --git a/src/main/java/com/thealgorithms/lineclipping/LiangBarsky.java b/src/main/java/com/thealgorithms/lineclipping/LiangBarsky.java new file mode 100644 index 000000000000..723e2bb2fbf9 --- /dev/null +++ b/src/main/java/com/thealgorithms/lineclipping/LiangBarsky.java @@ -0,0 +1,93 @@ +package com.thealgorithms.lineclipping; + +import com.thealgorithms.lineclipping.utils.Line; +import com.thealgorithms.lineclipping.utils.Point; + +/** + * @author shikarisohan + * @since 10/5/24 + * + * * The Liang-Barsky line clipping algorithm is an efficient algorithm for + * * line clipping against a rectangular window. It is based on the parametric + * * equation of a line and checks the intersections of the line with the + * * window boundaries. This algorithm calculates the intersection points, + * * if any, and returns the clipped line that lies inside the window. + * * + * * Reference: + * * https://en.wikipedia.org/wiki/Liang%E2%80%93Barsky_algorithm + * + * Clipping window boundaries are defined as (xMin, yMin) and (xMax, yMax). + * The algorithm computes the clipped line segment if it's partially or + * fully inside the clipping window. + */ +public class LiangBarsky { + + // Define the clipping window + double xMin; + double xMax; + double yMin; + double yMax; + + public LiangBarsky(double xMin, double yMin, double xMax, double yMax) { + this.xMin = xMin; + this.yMin = yMin; + this.xMax = xMax; + this.yMax = yMax; + } + + // Liang-Barsky algorithm to return the clipped line + public Line liangBarskyClip(Line line) { + double dx = line.end.x - line.start.x; + double dy = line.end.y - line.start.y; + + double[] p = {-dx, dx, -dy, dy}; + double[] q = {line.start.x - xMin, xMax - line.start.x, line.start.y - yMin, yMax - line.start.y}; + + double[] resultT = clipLine(p, q); + + if (resultT == null) { + return null; // Line is outside the clipping window + } + + return calculateClippedLine(line, resultT[0], resultT[1], dx, dy); + } + + // clip the line by adjusting t0 and t1 for each edge + private double[] clipLine(double[] p, double[] q) { + double t0 = 0.0; + double t1 = 1.0; + + for (int i = 0; i < 4; i++) { + double t = q[i] / p[i]; + if (p[i] == 0 && q[i] < 0) { + return null; // Line is outside the boundary + } else if (p[i] < 0) { + if (t > t1) { + return null; + } // Line is outside + if (t > t0) { + t0 = t; + } // Update t0 + } else if (p[i] > 0) { + if (t < t0) { + return null; + } // Line is outside + if (t < t1) { + t1 = t; + } // Update t1 + } + } + + return new double[] {t0, t1}; // Return valid t0 and t1 + } + + // calculate the clipped line based on t0 and t1 + private Line calculateClippedLine(Line line, double t0, double t1, double dx, double dy) { + double clippedX1 = line.start.x + t0 * dx; + double clippedY1 = line.start.y + t0 * dy; + double clippedX2 = line.start.x + t1 * dx; + double clippedY2 = line.start.y + t1 * dy; + + return new Line(new Point(clippedX1, clippedY1), new Point(clippedX2, clippedY2)); + } +} diff --git a/src/main/java/com/thealgorithms/lineclipping/utils/Line.java b/src/main/java/com/thealgorithms/lineclipping/utils/Line.java new file mode 100644 index 000000000000..56cd52e3cdce --- /dev/null +++ b/src/main/java/com/thealgorithms/lineclipping/utils/Line.java @@ -0,0 +1,43 @@ +package com.thealgorithms.lineclipping.utils; + +import java.util.Objects; + +/** + * @author moksedursohan + * @since 10/4/24 + */ +public class Line { + + public Point start; + public Point end; + + public Line() { + } + + public Line(Point start, Point end) { + this.start = start; + this.end = end; + } + + @Override + public boolean equals(Object o) { + if (this == o) { + return true; + } + if (!(o instanceof Line line)) { + return false; + } + + return Objects.equals(start, line.start) && Objects.equals(end, line.end); + } + + @Override + public int hashCode() { + return Objects.hash(start, end); + } + + @Override + public String toString() { + return "Line from " + start + " to " + end; + } +} diff --git a/src/main/java/com/thealgorithms/lineclipping/utils/Point.java b/src/main/java/com/thealgorithms/lineclipping/utils/Point.java new file mode 100644 index 000000000000..7ef58c783903 --- /dev/null +++ b/src/main/java/com/thealgorithms/lineclipping/utils/Point.java @@ -0,0 +1,43 @@ +package com.thealgorithms.lineclipping.utils; + +import java.util.Objects; + +/** + * @author moksedursohan + * @since 10/4/24 + */ +public class Point { + + public double x; + public double y; + + public Point() { + } + + public Point(double x, double y) { + this.x = x; + this.y = y; + } + + @Override + public boolean equals(Object o) { + if (this == o) { + return true; + } + if (!(o instanceof Point point)) { + return false; + } + + return Double.compare(x, point.x) == 0 && Double.compare(y, point.y) == 0; + } + + @Override + public int hashCode() { + return Objects.hash(x, y); + } + + @Override + public String toString() { + return "(" + x + ", " + y + ")"; + } +} diff --git a/src/test/java/com/thealgorithms/lineclipping/CohenSutherlandTest.java b/src/test/java/com/thealgorithms/lineclipping/CohenSutherlandTest.java new file mode 100644 index 000000000000..064f71a17c12 --- /dev/null +++ b/src/test/java/com/thealgorithms/lineclipping/CohenSutherlandTest.java @@ -0,0 +1,81 @@ +package com.thealgorithms.lineclipping; + +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertNotNull; +import static org.junit.jupiter.api.Assertions.assertNull; + +import com.thealgorithms.lineclipping.utils.Line; +import com.thealgorithms.lineclipping.utils.Point; +import org.junit.jupiter.api.Test; + +/** + * @author shikarisohan + * @since 10/4/24 + */ +class CohenSutherlandTest { + + // Define the clipping window (1.0, 1.0) to (10.0, 10.0) + CohenSutherland cs = new CohenSutherland(1.0, 1.0, 10.0, 10.0); + + @Test + void testLineCompletelyInside() { + // Line fully inside the clipping window + Line line = new Line(new Point(2.0, 2.0), new Point(8.0, 8.0)); + Line clippedLine = cs.cohenSutherlandClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(line, clippedLine, "Line inside the window should remain unchanged."); + } + + @Test + void testLineCompletelyOutside() { + // Line completely outside and above the clipping window + Line line = new Line(new Point(11.0, 12.0), new Point(15.0, 18.0)); + Line clippedLine = cs.cohenSutherlandClip(line); + + assertNull(clippedLine, "Line should be null because it's completely outside."); + } + + @Test + void testLinePartiallyInside() { + // Line partially inside the clipping window + Line line = new Line(new Point(5.0, 5.0), new Point(12.0, 12.0)); + Line expectedClippedLine = new Line(new Point(5.0, 5.0), new Point(10.0, 10.0)); // Clipped at (10, 10) + Line clippedLine = cs.cohenSutherlandClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(expectedClippedLine, clippedLine, "Line should be clipped correctly."); + } + + @Test + void testLineOnBoundary() { + // Line exactly on the boundary of the clipping window + Line line = new Line(new Point(1.0, 5.0), new Point(10.0, 5.0)); + Line clippedLine = cs.cohenSutherlandClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(line, clippedLine, "Line on the boundary should remain unchanged."); + } + + @Test + void testDiagonalLineThroughClippingWindow() { + // Diagonal line crossing from outside to outside through the window + Line line = new Line(new Point(0.0, 0.0), new Point(12.0, 12.0)); + Line expectedClippedLine = new Line(new Point(1.0, 1.0), new Point(10.0, 10.0)); // Clipped at both boundaries + Line clippedLine = cs.cohenSutherlandClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(expectedClippedLine, clippedLine, "Diagonal line should be clipped correctly."); + } + + @Test + void testVerticalLineClipping() { + // Vertical line crossing the top and bottom of the clipping window + Line line = new Line(new Point(5.0, 0.0), new Point(5.0, 12.0)); + Line expectedClippedLine = new Line(new Point(5.0, 1.0), new Point(5.0, 10.0)); // Clipped at yMin and yMax + Line clippedLine = cs.cohenSutherlandClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(expectedClippedLine, clippedLine, "Vertical line should be clipped correctly."); + } +} diff --git a/src/test/java/com/thealgorithms/lineclipping/LiangBarskyTest.java b/src/test/java/com/thealgorithms/lineclipping/LiangBarskyTest.java new file mode 100644 index 000000000000..1c48cd106572 --- /dev/null +++ b/src/test/java/com/thealgorithms/lineclipping/LiangBarskyTest.java @@ -0,0 +1,65 @@ +package com.thealgorithms.lineclipping; + +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertNotNull; +import static org.junit.jupiter.api.Assertions.assertNull; + +import com.thealgorithms.lineclipping.utils.Line; +import com.thealgorithms.lineclipping.utils.Point; +import org.junit.jupiter.api.Test; + +/** + * @author shikarisohan + * @since 10/5/24 + */ +class LiangBarskyTest { + + LiangBarsky lb = new LiangBarsky(1.0, 1.0, 10.0, 10.0); + + @Test + void testLineCompletelyInside() { + Line line = new Line(new Point(2.0, 2.0), new Point(8.0, 8.0)); + Line clippedLine = lb.liangBarskyClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(line, clippedLine, "Line inside the window should remain unchanged."); + } + + @Test + void testLineCompletelyOutside() { + Line line = new Line(new Point(12.0, 12.0), new Point(15.0, 18.0)); + Line clippedLine = lb.liangBarskyClip(line); + + assertNull(clippedLine, "Line should be null because it's completely outside."); + } + + @Test + void testLinePartiallyInside() { + Line line = new Line(new Point(5.0, 5.0), new Point(12.0, 12.0)); + Line expectedClippedLine = new Line(new Point(5.0, 5.0), new Point(10.0, 10.0)); // Clipped at (10, 10) + Line clippedLine = lb.liangBarskyClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(expectedClippedLine, clippedLine, "Line should be clipped correctly."); + } + + @Test + void testDiagonalLineThroughClippingWindow() { + Line line = new Line(new Point(0.0, 0.0), new Point(12.0, 12.0)); + Line expectedClippedLine = new Line(new Point(1.0, 1.0), new Point(10.0, 10.0)); // Clipped at both boundaries + Line clippedLine = lb.liangBarskyClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(expectedClippedLine, clippedLine, "Diagonal line should be clipped correctly."); + } + + @Test + void testVerticalLineClipping() { + Line line = new Line(new Point(5.0, 0.0), new Point(5.0, 12.0)); + Line expectedClippedLine = new Line(new Point(5.0, 1.0), new Point(5.0, 10.0)); // Clipped at yMin and yMax + Line clippedLine = lb.liangBarskyClip(line); + + assertNotNull(clippedLine, "Line should not be null."); + assertEquals(expectedClippedLine, clippedLine, "Vertical line should be clipped correctly."); + } +}