56 lines
1.8 KiB
JavaScript
56 lines
1.8 KiB
JavaScript
"use strict";
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// DuskPNG – PNG export using pngjs (window.PNG)
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// Falls back to canvas.toBlob if pngjs is unavailable.
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const DuskPNG = (() => {
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function _pngAvailable() {
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return typeof PNG !== "undefined" && PNG.sync && typeof PNG.sync.write === "function";
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}
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// Encode RGBA pixel data into a PNG Buffer via pngjs.
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// Returns a Uint8Array (Buffer) if pngjs is available, otherwise null.
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function encode(width, height, rgbaData) {
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if(!_pngAvailable()) return null;
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const png = new PNG({ width, height });
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const src = rgbaData instanceof Uint8ClampedArray
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? rgbaData
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: new Uint8ClampedArray(rgbaData);
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for(let i = 0; i < src.length; i++) {
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png.data[i] = src[i];
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}
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return PNG.sync.write(png); // returns a Buffer (Uint8Array subclass)
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}
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// Trigger a browser download of the RGBA data as a PNG file.
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function download(filename, width, height, rgbaData) {
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const buf = encode(width, height, rgbaData);
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if(buf) {
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// pngjs path
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const blob = new Blob([buf], { type: "image/png" });
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_triggerDownload(URL.createObjectURL(blob), filename);
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} else {
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// Canvas fallback
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const canvas = Object.assign(document.createElement("canvas"), { width, height });
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const ctx = canvas.getContext("2d");
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const src = rgbaData instanceof Uint8ClampedArray
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? rgbaData
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: new Uint8ClampedArray(rgbaData);
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ctx.putImageData(new ImageData(src, width, height), 0, 0);
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canvas.toBlob(blob => _triggerDownload(URL.createObjectURL(blob), filename), "image/png");
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}
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}
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function _triggerDownload(url, filename) {
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const a = Object.assign(document.createElement("a"), { href: url, download: filename });
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a.click();
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URL.revokeObjectURL(url);
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}
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return Object.freeze({ encode, download });
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})();
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