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Bug fix for issue #216: circle radius is computed more accurately now

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This commit is contained in:
Thomas Boch
2025-01-16 12:01:14 +01:00
parent 921d395cb2
commit c620069c18
1 changed files with 36 additions and 6 deletions
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42
src/js/shapes/Circle.js
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@@ -222,21 +222,50 @@ export let Circle = (function() {
let hidden = true;
var ra, dec, vertOnCircle, dx, dy;
this.radius = Number.NEGATIVE_INFINITY;
// Project 4 points lying on the circle and take the minimal dist with the center as radius
[[-1, 0], [1, 0], [0, -1], [0, 1]].forEach(([cardDirRa, cardDirDec]) => {
ra = this.centerRaDec[0] + cardDirRa * this.radiusDegrees;
dec = this.centerRaDec[1] + cardDirDec * this.radiusDegrees;
const degToRad = Math.PI / 180;
const radToDeg = 180 / Math.PI;
const sampleCoordinates = [];
const radiusRadians = this.radiusDegrees * degToRad;
const raCenterRadians = this.centerRaDec[0] * degToRad;
const decCenterRadians = this.centerRaDec[1] * degToRad;
// compute 4 sample coordinates lying on the circle
for (let i = 0; i < 4; i++) {
const phi = i * 2 * Math.PI / 4;
const sampleDec = Math.asin(
Math.sin(decCenterRadians) * Math.cos(radiusRadians) +
Math.cos(decCenterRadians) * Math.sin(radiusRadians) * Math.cos(phi)
);
const sampleRa = raCenterRadians + Math.atan2(
Math.sin(phi) * Math.sin(radiusRadians) * Math.cos(decCenterRadians),
Math.cos(radiusRadians) - Math.sin(decCenterRadians) * Math.sin(sampleDec)
);
// Normalize RA to [0, 2π] and convert to degrees
const sampleRaDeg = radToDeg * ((sampleRa + 2 * Math.PI) % (2 * Math.PI));
const sampleDecDeg = radToDeg * sampleDec;
sampleCoordinates.push([sampleRaDeg, sampleDecDeg]);
}
let vertOnCircle, dx, dy;
this.radius = Number.NEGATIVE_INFINITY;
sampleCoordinates.forEach(([ra, dec]) => {
vertOnCircle = view.aladin.world2pix(ra, dec);
if (vertOnCircle) {
dx = vertOnCircle[0] - this.center.x;
dy = vertOnCircle[1] - this.center.y;
this.radius = Math.max(Math.sqrt(dx*dx + dy*dy), this.radius);
if (this.radius !== Number.NEGATIVE_INFINITY) {
this.radius = Math.min(Math.sqrt(dx*dx + dy*dy), this.radius);
}
else {
this.radius = Math.sqrt(dx*dx + dy*dy);
}
hidden = false;
}
@@ -245,6 +274,7 @@ export let Circle = (function() {
if (hidden) {
return false;
}
// Then we can draw
var baseColor = this.color;