31 lines
879 B
TypeScript
31 lines
879 B
TypeScript
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export function getZoomOrigin(canvas: HTMLCanvasElement | null) {
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if (canvas === null) {
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return { x: 0, y: 0 };
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}
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const context = canvas.getContext("2d");
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if (context === null) {
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return { x: 0, y: 0 };
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}
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const normalizedCanvasWidth = canvas.width / context.getTransform().a;
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const normalizedCanvasHeight = canvas.height / context.getTransform().d;
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return {
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x: normalizedCanvasWidth / 2,
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y: normalizedCanvasHeight / 2,
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};
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}
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export function getZoomTranslation(canvas: HTMLCanvasElement, zoom: number) {
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const diffMiddleOfTheCanvas = {
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x: (canvas.width / 2) * (zoom - 1),
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y: (canvas.height / 2) * (zoom - 1),
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};
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// Due to JavaScript float precision, we fix to fix decimals count to have symmetric zoom
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return {
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x: parseFloat(diffMiddleOfTheCanvas.x.toFixed(8)),
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y: parseFloat(diffMiddleOfTheCanvas.y.toFixed(8)),
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};
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}
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