79 lines
2.5 KiB
HTML
79 lines
2.5 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<title>In-Browser Greyscale converter</title>
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<meta charset="utf-8" />
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<script src="https://unpkg.com/canvaskit-wasm@0.6.0/bin/canvaskit.js"></script>
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<script type="text/javascript" src="/impl/impl.js"></script>
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<style>
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canvas {
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border: 1px dashed black;
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width: 400px;
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height: 400px;
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}
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#original {
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display:none;
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}
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</style>
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<body>
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<input type=file name=file id=file @change=${ele._onFileChange}/>
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<canvas id=original></canvas>
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<canvas id=grey></canvas>
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<script type="text/javascript" charset="utf-8">
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loadPolyfill().then(() => {
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function drawImageAndGreyscaleImg(imgData) {
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const gCanvas = document.querySelector('#grey');
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gCanvas.width = imgData.width;
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gCanvas.height = imgData.height;
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const gCtx = gCanvas.getContext('2d');
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const pixels = imgData.data;
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for (let y = 0; y < imgData.height; y++) {
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for (let x = 0; x < imgData.width; x++) {
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const offset = 4*(x + imgData.width*y)
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const r = pixels[offset], g = pixels[offset + 1], b = pixels[offset + 2];
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const grey = (r + g + b)/3;
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pixels[offset ] = grey;
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pixels[offset + 1] = grey;
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pixels[offset + 2] = grey;
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}
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}
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const greyData = new ImageData(pixels, imgData.width, imgData.height);
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gCtx.putImageData(greyData, 0, 0);
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}
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document.querySelector('#file').addEventListener('change', (e) => {
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const blobToLoad = e.target.files[0];
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// A browser implementation would be able to directly take the blob
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const reader = new FileReader();
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reader.addEventListener('load', () => {
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const bytes = reader.result;
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const imgData = window.createImageData(bytes, {
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// Specify the destination properties, that is, what format to translate
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// the pixels in the image to.
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pixelWidth: "uint8",
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premul: true,
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colorSpace: "srgb",
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});
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requestAnimationFrame(() => {
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drawImageAndGreyscaleImg(imgData);
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});
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});
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reader.addEventListener('error', () => {
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console.error('Failed to load '+ blobToLoad.name);
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});
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reader.readAsArrayBuffer(blobToLoad);
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});
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});
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</script>
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<body>
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</html>
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