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August 31, 2018 14:46
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Loupe on html5 canvas.
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| /** | |
| * canvas_loupe.js | |
| */ | |
| var loupe = { | |
| x: 0, // Current x. | |
| y: 0, // Current y. | |
| w: 0, // Image width. | |
| h: 0, // Image height. | |
| loupe_x: 50, // loupe x coordinate. | |
| loupe_y: 50, // loupe y coordinate. | |
| size: 50, // Crop size. | |
| zoom: 2, // Zoom rate. | |
| wide_size: 0, // Crop size * Zoom rate. | |
| image: null, // Image object. | |
| /** | |
| * Initialize. | |
| * | |
| * @param w Image width | |
| * @param h Image height | |
| * @param src Image src | |
| */ | |
| initialize: function(w, h, src) { | |
| this.w = w; | |
| this.h = h; | |
| this.wide_size = this.size * this.zoom; | |
| this.image = new Image(); | |
| this.image.src = src; | |
| }, | |
| /** | |
| * Update coordinate. | |
| * | |
| * @param x | |
| * @param y | |
| */ | |
| update: function(x, y) { | |
| this.x = x; | |
| this.y = y; | |
| }, | |
| /** | |
| * Draw loupe. | |
| * | |
| * @param ctx context | |
| */ | |
| draw: function(ctx) { | |
| var nx = (this.x * this.image.naturalWidth / this.w) - (this.size / 2); | |
| var ny = (this.y * this.image.naturalHeight / this.h) - (this.size / 2); | |
| ctx.save(); | |
| ctx.beginPath(); | |
| ctx.arc(this.loupe_x + this.wide_size / 2, | |
| this.loupe_y + this.wide_size / 2, this.wide_size / 2, 0, Math.PI * 2, false); | |
| ctx.clip(); | |
| ctx.drawImage(this.image, nx, ny, this.size, this.size, | |
| this.loupe_x, this.loupe_y, this.wide_size, this.wide_size); | |
| ctx.restore(); | |
| } | |
| }; |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>loupe</title> | |
| <script type="text/javascript" src="canvas_loupe.js"></script> | |
| <script type="text/javascript" src="index.js"></script> | |
| <style> | |
| #container { | |
| position: relative; | |
| } | |
| #main_img { | |
| width: 640px; | |
| height: 480px; | |
| position: absolute; | |
| z-index: 1; | |
| } | |
| #loupe_canvas { | |
| position: absolute; | |
| z-index: 2; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div id="container"> | |
| <img id="main_img" src="sample.jpg"></img> | |
| <canvas id="loupe_canvas" width="640" height="480"></canvas> | |
| </div> | |
| </body> | |
| </html> |
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| var ctx = null; | |
| window.onload = function() { | |
| var canvas = document.getElementById('loupe_canvas'); | |
| ctx = canvas.getContext('2d'); | |
| canvas.addEventListener('mousemove', onMouseMove); | |
| loupe.initialize(640, 480, 'sample.jpg'); | |
| }; | |
| function onMouseMove(e) { | |
| loupe.update(e.clientX, e.clientY); | |
| loupe.draw(ctx); | |
| } |
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