Created
January 18, 2021 07:32
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draw your data
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| var img = new Image(); | |
| var canvas = document.getElementById('canvas'); | |
| var ctx = canvas.getContext('2d'); | |
| let coords = []; | |
| img.onload = function() { | |
| ctx.drawImage(img, 0, 0); | |
| }; | |
| function clearPixel(x,y) { | |
| var pixel = ctx.getImageData(x, y, 1, 1); | |
| pixel.data[3] = 0; | |
| ctx.putImageData(pixel,x,y); | |
| } | |
| function pick(event) { | |
| var x = event.layerX; | |
| var y = event.layerY; | |
| if(coords[x]){ | |
| clearPixel(x,coords[x]) | |
| } | |
| var pixel = ctx.getImageData(x, y, 1, 1); | |
| coords[x] = y; | |
| pixel.data[0] = 0; | |
| pixel.data[1] = 0; | |
| pixel.data[2] = 255; | |
| pixel.data[3] = 255; | |
| ctx.putImageData(pixel,x,y); | |
| } | |
| canvas.addEventListener('mousemove', function(event) { | |
| pick(event); | |
| }); | |
| document.getElementById('clear').addEventListener('click', function(){ | |
| coords = []; | |
| ctx.clearRect(0, 0, canvas.width, canvas.height); | |
| document.getElementById("output").innerHTML = "" | |
| }); | |
| document.getElementById('showvalues').addEventListener('click', function(){ | |
| let valueString = ""; | |
| let htmlstring = "<p>x,y</p>" | |
| coords.forEach((d,i)=>{ | |
| valueString = valueString + i + "," + (canvas.height - d) + "\n"; | |
| htmlstring = htmlstring + "<p>" + i + "," + (canvas.height - d) + "</p>" | |
| }); | |
| console.log(valueString); | |
| document.getElementById("output").innerHTML = htmlstring; | |
| }); |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Draw a curve, get coords</title> | |
| <style> | |
| #canvas { | |
| border: solid 5px; | |
| margin: 20px; | |
| } | |
| .clickable { | |
| cursor: pointer | |
| } | |
| p { | |
| margin: 0px 0px 0px 20px | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <h1>Draw a function</h1> | |
| <div> | |
| <p>Note: only one value per x coord will be allowed.</p> | |
| <canvas id="canvas" width="500" height="300"></canvas> | |
| <p id="clear" class="clickable">*click to clear*</p> | |
| <p id="showvalues" class="clickable">*click to paste coordinates*</p> | |
| <div id="output"></div> | |
| </div> | |
| <script src="drawacurve.js"></script> | |
| </body> | |
| </html |
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