97 lines
2.1 KiB
JavaScript
97 lines
2.1 KiB
JavaScript
import { Vec2 } from "./point.mjs";
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export class Transform {
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constructor(xx, yx, xy, yy, x, y) {
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this.xx = xx;
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this.yx = yx;
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this.xy = xy;
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this.yy = yy;
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this.x = x;
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this.y = y;
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}
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static Id() {
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return new Transform(1, 0, 0, 1, 0, 0);
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}
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static Translate(x, y) {
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return new Transform(1, 0, 0, 1, x, y);
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}
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applyX(x, y) {
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return x * this.xx + y * this.yx + this.x;
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}
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applyY(x, y) {
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return x * this.xy + y * this.yy + this.y;
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}
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applyXY(x, y) {
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return new Vec2(this.applyX(x, y), this.applyY(x, y));
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}
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applyToSink(pt, sink) {
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sink.x = this.applyX(pt.x, pt.y);
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sink.y = this.applyY(pt.x, pt.y);
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}
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apply(pt) {
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return this.applyXY(pt.x, pt.y);
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}
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applyOffset(delta) {
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return this.applyOffsetXY(delta.x, delta.y);
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}
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applyOffsetXY(deltaX, deltaY) {
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return {
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x: deltaX * this.xx + deltaY * this.yx,
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y: deltaX * this.xy + deltaY * this.yy
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};
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}
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unapplyToSink(pt, sink) {
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const xx = pt.x - this.x;
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const yy = pt.y - this.y;
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const denom = this.xx * this.yy - this.xy * this.yx;
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sink.x = (xx * this.yy - yy * this.yx) / denom;
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sink.y = (yy * this.xx - xx * this.xy) / denom;
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}
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unapply(pt) {
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let sink = new Vec2(0, 0);
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this.unapplyToSink(pt, sink);
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return sink;
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}
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inverse() {
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const denom = this.xx * this.yy - this.xy * this.yx;
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return new Transform(
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this.yy / denom,
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-this.yx / denom,
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-this.xy / denom,
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this.xx / denom,
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-(this.x * this.yy - this.y * this.yx) / denom,
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-(-this.x * this.xy + this.y * this.xx) / denom
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);
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}
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toString() {
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return `[[${this.xx} ${this.xy}] [${this.yx} ${this.yy}]] + [[${this.x}] [${this.y}]]`;
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}
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static isTranslate(tfm) {
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return tfm.xx === 1 && tfm.yy === 1 && tfm.xy === 0 && tfm.yx === 0;
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}
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static isIdentity(tfm) {
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return this.isTranslate(tfm) && tfm.x === 0 && tfm.y === 0;
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}
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static Combine(...tfms) {
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let z00 = new Vec2(0, 0);
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let z10 = new Vec2(1, 0);
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let z01 = new Vec2(0, 1);
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for (const tfm of tfms) {
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z00 = tfm.apply(z00);
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z10 = tfm.apply(z10);
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z01 = tfm.apply(z01);
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}
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return new Transform(
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z10.x - z00.x,
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z01.x - z00.x,
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z10.y - z00.y,
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z01.y - z00.y,
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z00.x,
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z00.y
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);
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}
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}
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