39 lines
1.2 KiB
JavaScript
39 lines
1.2 KiB
JavaScript
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import { BoundingBox } from "./BoundingBox.mjs";
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function checkRow(data, width, y) {
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for (let x = 0, index = 4 * y * width; x < width; ++x, index += 4)
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if (data[index + 3] !== 0)
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return !1;
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return !0;
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}
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function checkColumn(data, width, x, top, bottom) {
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const stride = 4 * width;
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for (let y = top, index = top * stride + 4 * x; y <= bottom; ++y, index += stride)
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if (data[index + 3] !== 0)
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return !1;
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return !0;
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}
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function getCanvasBoundingBox(canvas) {
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const { width, height } = canvas, context = canvas.getContext("2d", {
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willReadFrequently: !0
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});
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if (context === null)
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throw new TypeError("Failed to get canvas 2D context");
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const data = context.getImageData(0, 0, width, height).data;
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let left = 0, top = 0, right = width - 1, bottom = height - 1;
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for (; top < height && checkRow(data, width, top); )
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++top;
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if (top === height)
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return BoundingBox.EMPTY;
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for (; checkRow(data, width, bottom); )
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--bottom;
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for (; checkColumn(data, width, left, top, bottom); )
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++left;
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for (; checkColumn(data, width, right, top, bottom); )
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--right;
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return ++right, ++bottom, new BoundingBox(left, top, right, bottom);
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}
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export {
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getCanvasBoundingBox
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};
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//# sourceMappingURL=getCanvasBoundingBox.mjs.map
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