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js/spine-visible-bounds.js

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+'use strict';
+
+function findAlphaBounds(rgba, width, height, threshold = 4) {
+	let left = width, top = height, right = 0, bottom = 0;
+	for (let y = 0; y < height; y++) {
+		for (let x = 0; x < width; x++) {
+			if (rgba[(y * width + x) * 4 + 3] <= threshold) continue;
+			left = Math.min(left, x);
+			top = Math.min(top, y);
+			right = Math.max(right, x + 1);
+			bottom = Math.max(bottom, y + 1);
+		}
+	}
+	return right > left && bottom > top ? { left, top, right, bottom } : null;
+}
+
+function toWorldBounds(pixels, width, height, scale, centerX, centerY) {
+	if (!pixels || !isFinite(scale) || scale <= 0) return null;
+	const left = centerX + (pixels.left - width / 2) / scale;
+	const right = centerX + (pixels.right - width / 2) / scale;
+	const top = centerY - (pixels.top - height / 2) / scale;
+	const bottom = centerY - (pixels.bottom - height / 2) / scale;
+	return { x: left, y: bottom, width: right - left, height: top - bottom };
+}
+
+module.exports = { findAlphaBounds, toWorldBounds };