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feat: implement perspective warp #484

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155 changes: 155 additions & 0 deletions src/geometry/__tests__/getPerspectiveWarp.test.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,155 @@
import { Image } from '../../Image.js';
import getPerspectiveWarp from '../getPerspectiveWarp.js';

describe('warping tests', () => {
it('resize without rotation', () => {
const image = new Image(3, 3, {
data: new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 9]),
colorModel: 'GREY',
});
const points = [
{ column: 0, row: 0 },
{ column: 2, row: 0 },
{ column: 1, row: 2 },
{ column: 0, row: 2 },
];
const matrix = getPerspectiveWarp(points);
const result = image.transform(matrix, { inverse: true });
expect(result.width).not.toBeLessThan(2);
expect(result.height).not.toBeLessThan(2);
expect(result.width).not.toBeGreaterThan(3);
expect(result.height).not.toBeGreaterThan(3);
});
it('resize without rotation 2', () => {
const image = new Image(4, 4, {
data: new Uint8Array([
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
]),
colorModel: 'GREY',
});

const points = [
{ column: 0, row: 0 },
{ column: 3, row: 0 },
{ column: 2, row: 1 },
{ column: 0, row: 1 },
];
const matrix = getPerspectiveWarp(points);
const result = image.transform(matrix, { inverse: true });
expect(result.width).not.toBeLessThan(3);
expect(result.height).not.toBeLessThan(1);
expect(result.width).not.toBeGreaterThan(4);
expect(result.height).not.toBeGreaterThan(4);
});
});

describe('openCV comparison', () => {
test('nearest interpolation plants', () => {
const image = testUtils.load('various/plants.png');
const openCvResult = testUtils.load(
'opencv/test_perspective_warp_plants_nearest.png',
);

const points = [
{ column: 858.5, row: 9 },
{ column: 911.5, row: 786 },
{ column: 154.5, row: 611 },
{ column: 166.5, row: 195 },
];
const matrix = getPerspectiveWarp(points, {
width: 1080,
height: 810,
});
const result = image.transform(matrix, {
inverse: true,
interpolationType: 'nearest',
});
const croppedPieceOpenCv = openCvResult.crop({
origin: { column: 45, row: 0 },
width: 100,
height: 100,
});

const croppedPiece = result.crop({
origin: { column: 45, row: 0 },
width: 100,
height: 100,
});

expect(result.width).toEqual(openCvResult.width);
expect(result.height).toEqual(openCvResult.height);
expect(croppedPiece).toEqual(croppedPieceOpenCv);
});

test('nearest interpolation card', () => {
const image = testUtils.load('various/card.png');
const openCvResult = testUtils.load(
'opencv/test_perspective_warp_card_nearest.png',
);
const points = [
{ column: 145, row: 460 },
{ column: 55, row: 140 },
{ column: 680, row: 38 },
{ column: 840, row: 340 },
];
const matrix = getPerspectiveWarp(points, {
width: 700,
height: 400,
});
const result = image.transform(matrix, {
inverse: true,
interpolationType: 'nearest',
width: 700,
height: 400,
});
const croppedPieceOpenCv = openCvResult.crop({
origin: { column: 45, row: 0 },
width: 5,
height: 5,
});

const croppedPiece = result.crop({
origin: { column: 45, row: 0 },
width: 5,
height: 5,
});

expect(result.width).toEqual(openCvResult.width);
expect(result.height).toEqual(openCvResult.height);
expect(croppedPiece).toEqual(croppedPieceOpenCv);
});
test('nearest interpolation plants', () => {
const image = testUtils.load('various/plants.png');
const openCvResult = testUtils.load(
'opencv/test_perspective_warp_plants_linear.png',
);

const points = [
{ column: 858.5, row: 9 },
{ column: 166.5, row: 195 },
{ column: 154.5, row: 611 },
{ column: 911.5, row: 786 },
];
const matrix = getPerspectiveWarp(points, {
width: 1080,
height: 810,
});
const result = image.transform(matrix, {
inverse: true,
interpolationType: 'nearest',
});

expect(result.width).toEqual(openCvResult.width);
expect(result.height).toEqual(openCvResult.height);
});
});

describe('error testing', () => {
test("should throw if there aren't 4 points", () => {
expect(() => {
getPerspectiveWarp([{ column: 1, row: 1 }]);
}).toThrow(
'The array pts must have four elements, which are the four corners. Currently, pts have 1 elements',
);
});
});
2 changes: 1 addition & 1 deletion src/geometry/__tests__/transform.test.ts
Original file line number Diff line number Diff line change
Expand Up @@ -121,5 +121,5 @@ test('should throw if matrix has wrong size', () => {
];
expect(() => {
img.transform(translation);
}).toThrow('transformation matrix must be 2x3. Received 2x4');
}).toThrow('transformation matrix must be 2x3 or 3x3. Received 2x4');
});
149 changes: 149 additions & 0 deletions src/geometry/getPerspectiveWarp.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,149 @@
import { Matrix, SingularValueDecomposition } from 'ml-matrix';

import type { Point } from '../utils/geometry/points.js';

interface GetPerspectiveWarpOptions {
width?: number;
height?: number;
}

// REFERENCES :
// https://stackoverflow.com/questions/38285229/calculating-aspect-ratio-of-perspective-transform-destination-image/38402378#38402378
// http://www.corrmap.com/features/homography_transformation.php
// https://ags.cs.uni-kl.de/fileadmin/inf_ags/3dcv-ws11-12/3DCV_WS11-12_lec04.pdf
// http://graphics.cs.cmu.edu/courses/15-463/2011_fall/Lectures/morphing.pdf
/**
* Returns perspective warp matrix from 4 points.
* @param pts - 4 reference corners of the new image.
* @param options - PerspectiveWarpOptions
* @returns - Matrix from 4 points.
*/
export default function getPerspectiveWarp(
pts: Point[],
options: GetPerspectiveWarpOptions = {},
) {
if (pts.length !== 4) {
throw new Error(
`The array pts must have four elements, which are the four corners. Currently, pts have ${pts.length} elements`,
);
}
const { width, height } = options;
const [tl, tr, br, bl] = order4Points(pts);

let widthRect;
let heightRect;
if (height && width) {
widthRect = width;
heightRect = height;
} else {
widthRect = Math.ceil(
Math.max(distance2Points(tl, tr), distance2Points(bl, br)),
);
heightRect = Math.ceil(
Math.max(distance2Points(tl, bl), distance2Points(tr, br)),
);
}

const [x1, y1] = [0, 0];
const [x2, y2] = [widthRect - 1, 0];
const [x3, y3] = [widthRect - 1, heightRect - 1];
const [x4, y4] = [0, heightRect - 1];

const S = new Matrix([
[x1, y1, 1, 0, 0, 0, -x1 * tl.column, -y1 * tl.column],
[x2, y2, 1, 0, 0, 0, -x2 * tr.column, -y2 * tr.column],
[x3, y3, 1, 0, 0, 0, -x3 * br.column, -y3 * br.column],
[x4, y4, 1, 0, 0, 0, -x4 * bl.column, -y4 * bl.column],
[0, 0, 0, x1, y1, 1, -x1 * tl.row, -y1 * tl.row],
[0, 0, 0, x2, y2, 1, -x2 * tr.row, -y2 * tr.row],
[0, 0, 0, x3, y3, 1, -x3 * br.row, -y3 * br.row],
[0, 0, 0, x4, y4, 1, -x4 * bl.row, -y4 * bl.row],
]);
const D = Matrix.columnVector([
tl.column,
tr.column,
br.column,
bl.column,
tl.row,
tr.row,
br.row,
bl.row,
]);

const svd = new SingularValueDecomposition(S);
const T = svd.solve(D).to1DArray(); // solve S*T = D
T.push(1);

const M = [];
for (let i = 0; i < 3; i++) {
const row = [];
for (let j = 0; j < 3; j++) {
row.push(T[i * 3 + j]);
}
M.push(row);
}
return M;
}

/**
* Sorts 4 points in order =>[top-left,top-right,bottom-right,bottom-left]. Input points must be in clockwise or counter-clockwise order.
* @param pts - Array of 4 points.
* @returns Sorted array of 4 points.
*/
function order4Points(pts: Point[]) {
let tl: Point;
let tr: Point;
let br: Point;
let bl: Point;

let minX = pts[0].column;
let indexMinX = 0;

for (let i = 1; i < pts.length; i++) {
if (pts[i].column < minX) {
minX = pts[i].column;
indexMinX = i;
}
}

let minX2 = pts[(indexMinX + 1) % pts.length].column;
let indexMinX2 = (indexMinX + 1) % pts.length;

for (let i = 0; i < pts.length; i++) {
if (pts[i].column < minX2 && i !== indexMinX) {
minX2 = pts[i].column;
indexMinX2 = i;
}
}
if (pts[indexMinX2].row < pts[indexMinX].row) {
tl = pts[indexMinX2];
bl = pts[indexMinX];
if (indexMinX !== (indexMinX2 + 1) % 4) {
tr = pts[(indexMinX2 + 1) % 4];
br = pts[(indexMinX2 + 2) % 4];
} else {
tr = pts[(indexMinX2 + 2) % 4];
br = pts[(indexMinX2 + 3) % 4];
}
} else {
bl = pts[indexMinX2];
tl = pts[indexMinX];
if (indexMinX2 !== (indexMinX + 1) % 4) {
tr = pts[(indexMinX + 1) % 4];
br = pts[(indexMinX + 2) % 4];
} else {
tr = pts[(indexMinX + 2) % 4];
br = pts[(indexMinX + 3) % 4];
}

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}
return [tl, tr, br, bl];
}
/**
* Calculates distance between points.
* @param p1 - Point1
* @param p2 - Point2
* @returns distance between points.
*/
function distance2Points(p1: Point, p2: Point) {
return Math.hypot(p1.column - p2.column, p1.row - p2.row);
}
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