70 lines
2.8 KiB
JavaScript
70 lines
2.8 KiB
JavaScript
/**
|
|
* Calculates the Euclidean distance transform of a binary mask.
|
|
* Uses a two-pass algorithm for efficiency.
|
|
* @param binaryMask - Binary mask where 1 = inside, 0 = outside
|
|
* @param width - Width of the mask
|
|
* @param height - Height of the mask
|
|
* @returns Float32Array containing distance values
|
|
*/
|
|
export function calculateDistanceTransform(binaryMask, width, height) {
|
|
const distances = new Float32Array(width * height);
|
|
const infinity = width + height; // A value larger than any possible distance
|
|
// Initialize distances
|
|
for (let i = 0; i < width * height; i++) {
|
|
distances[i] = binaryMask[i] === 1 ? infinity : 0;
|
|
}
|
|
// Forward pass (top-left to bottom-right)
|
|
for (let y = 0; y < height; y++) {
|
|
for (let x = 0; x < width; x++) {
|
|
const idx = y * width + x;
|
|
if (distances[idx] > 0) {
|
|
let minDist = distances[idx];
|
|
// Check top neighbor
|
|
if (y > 0) {
|
|
minDist = Math.min(minDist, distances[(y - 1) * width + x] + 1);
|
|
}
|
|
// Check left neighbor
|
|
if (x > 0) {
|
|
minDist = Math.min(minDist, distances[y * width + (x - 1)] + 1);
|
|
}
|
|
// Check top-left diagonal
|
|
if (x > 0 && y > 0) {
|
|
minDist = Math.min(minDist, distances[(y - 1) * width + (x - 1)] + Math.sqrt(2));
|
|
}
|
|
// Check top-right diagonal
|
|
if (x < width - 1 && y > 0) {
|
|
minDist = Math.min(minDist, distances[(y - 1) * width + (x + 1)] + Math.sqrt(2));
|
|
}
|
|
distances[idx] = minDist;
|
|
}
|
|
}
|
|
}
|
|
// Backward pass (bottom-right to top-left)
|
|
for (let y = height - 1; y >= 0; y--) {
|
|
for (let x = width - 1; x >= 0; x--) {
|
|
const idx = y * width + x;
|
|
if (distances[idx] > 0) {
|
|
let minDist = distances[idx];
|
|
// Check bottom neighbor
|
|
if (y < height - 1) {
|
|
minDist = Math.min(minDist, distances[(y + 1) * width + x] + 1);
|
|
}
|
|
// Check right neighbor
|
|
if (x < width - 1) {
|
|
minDist = Math.min(minDist, distances[y * width + (x + 1)] + 1);
|
|
}
|
|
// Check bottom-right diagonal
|
|
if (x < width - 1 && y < height - 1) {
|
|
minDist = Math.min(minDist, distances[(y + 1) * width + (x + 1)] + Math.sqrt(2));
|
|
}
|
|
// Check bottom-left diagonal
|
|
if (x > 0 && y < height - 1) {
|
|
minDist = Math.min(minDist, distances[(y + 1) * width + (x - 1)] + Math.sqrt(2));
|
|
}
|
|
distances[idx] = minDist;
|
|
}
|
|
}
|
|
}
|
|
return distances;
|
|
}
|