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August 19, 2020 14:38
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Some types of compression in js
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| async function encode(input) { | |
| // TODO: handle unicode? | |
| const canvas = document.createElement("canvas"); | |
| canvas.width = Math.ceil(input.length / 3) + 8; | |
| canvas.height = 1; | |
| const ctx = canvas.getContext('2d'); | |
| const imgData = ctx.createImageData(canvas.width, 1); | |
| for (let i = 0, j = 0; i < 7; i++) | |
| imgData.data[i] = i % 4 == 3 ? 255 : (input.length >>> (8 * j++)) & 0xff; | |
| for (let i = 7, j = 0; i < 4 * canvas.width; i++) | |
| imgData.data[i] = i % 4 == 3 ? 255 : input.charCodeAt(j++) || 0; | |
| ctx.putImageData(imgData, 0, 0); | |
| return canvas.toDataURL('image/png', 0); | |
| } | |
| async function decode(input) { | |
| console.log(input) | |
| const image = new Image(); | |
| image.src = input; | |
| await new Promise(r => image.onload = r); | |
| const canvas = document.createElement("canvas"); | |
| canvas.width = image.width; | |
| const ctx = canvas.getContext('2d'); | |
| ctx.drawImage(image, 0, 0); | |
| const imgData = ctx.getImageData(0, 0, image.width, 1); | |
| let length = 0; | |
| for (let i = 0, j = 0; i < 7; i++) | |
| length |= i % 4 == 3 ? 0 : (imgData.data[i] << (8 * j++)); | |
| let output = ""; | |
| for (let i = 7; i < imgData.data.length; i++) | |
| output += i % 4 == 3 ? "" : String.fromCharCode(imgData.data[i]); | |
| return output.substr(0, length); | |
| } | |
| // Both minified | |
| async function encode(t){const e=document.createElement("canvas");e.width=Math.ceil(t.length/3)+8,e.height=1;const a=e.getContext("2d"),n=a.createImageData(e.width,1);for(let e=0,a=0;e<7;e++)n.data[e]=e%4==3?255:t.length>>>8*a++&255;for(let a=7,o=0;a<4*e.width;a++)n.data[a]=a%4==3?255:t.charCodeAt(o++)||0;return a.putImageData(n,0,0),e.toDataURL("image/png",0)}async function decode(t){console.log(t);const e=new Image;e.src=t,await new Promise(t=>e.onload=t);const a=document.createElement("canvas");a.width=e.width;const n=a.getContext("2d");n.drawImage(e,0,0);const o=n.getImageData(0,0,e.width,1);let c=0;for(let t=0,e=0;t<7;t++)c|=t%4==3?0:o.data[t]<<8*e++;let d="";for(let t=7;t<o.data.length;t++)d+=t%4==3?"":String.fromCharCode(o.data[t]);return d.substr(0,c)} |
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