54 lines
1.8 KiB
Java
54 lines
1.8 KiB
Java
package org.thoughtcrime.securesms.util;
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import android.graphics.PointF;
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import androidx.annotation.NonNull;
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public class MathUtils {
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/**
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* For more info:
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* <a href="http://math.stackexchange.com/questions/190111/how-to-check-if-a-point-is-inside-a-rectangle">StackOverflow: How to check point is in rectangle</a>
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*
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* @param pt point to check
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* @param v1 vertex 1 of the triangle
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* @param v2 vertex 2 of the triangle
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* @param v3 vertex 3 of the triangle
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* @return true if point (x, y) is inside the triangle
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*/
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public static boolean pointInTriangle(@NonNull PointF pt, @NonNull PointF v1,
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@NonNull PointF v2, @NonNull PointF v3) {
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boolean b1 = crossProduct(pt, v1, v2) < 0.0f;
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boolean b2 = crossProduct(pt, v2, v3) < 0.0f;
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boolean b3 = crossProduct(pt, v3, v1) < 0.0f;
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return (b1 == b2) && (b2 == b3);
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}
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/**
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* calculates cross product of vectors AB and AC
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*
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* @param a beginning of 2 vectors
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* @param b end of vector 1
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* @param c end of vector 2
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* @return cross product AB * AC
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*/
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private static float crossProduct(@NonNull PointF a, @NonNull PointF b, @NonNull PointF c) {
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return crossProduct(a.x, a.y, b.x, b.y, c.x, c.y);
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}
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/**
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* calculates cross product of vectors AB and AC
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*
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* @param ax X coordinate of point A
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* @param ay Y coordinate of point A
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* @param bx X coordinate of point B
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* @param by Y coordinate of point B
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* @param cx X coordinate of point C
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* @param cy Y coordinate of point C
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* @return cross product AB * AC
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*/
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private static float crossProduct(float ax, float ay, float bx, float by, float cx, float cy) {
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return (ax - cx) * (by - cy) - (bx - cx) * (ay - cy);
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}
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} |