Created
July 31, 2019 22:18
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crossfading image over canvas
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title>TODO supply a title</title> | |
| <meta charset="UTF-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> | |
| </head> | |
| <body> | |
| <canvas id="main_canvas" width="500" height="300"></canvas> | |
| <script> | |
| var canvas = document.getElementById('main_canvas'); | |
| var img = new Image(); | |
| img.onload = function(){ | |
| canvas.getContext('2d').drawImage(img, 0, 0); | |
| fadeTo(canvas, "2.jpg").then(()=>console.log("farts")); | |
| }; | |
| img.src = "1.jpg"; | |
| function fadeTo(canvas, imguri, x=0, y=0){ | |
| const loadImg = uri => new Promise(done=>{ | |
| var img = new Image(); | |
| img.onload = ()=>done(img); | |
| img.src = uri; | |
| }); | |
| return new Promise(async done => { | |
| var first_canvas = document.createElement('canvas'); | |
| first_canvas.width = canvas.width; | |
| first_canvas.height = canvas.height; | |
| var first = first_canvas.getContext('2d'); | |
| var first_img = await loadImg(canvas.toDataURL()); | |
| var next_canvas = document.createElement('canvas'); | |
| next_canvas.width = canvas.width; | |
| next_canvas.height = canvas.height; | |
| var next = next_canvas.getContext('2d'); | |
| var next_img = await loadImg(imguri); | |
| var ctx = canvas.getContext('2d'); | |
| var opacity = 1; | |
| const fade = ()=>{ | |
| opacity -= .02; | |
| first.clearRect(0, 0, canvas.width, canvas.height); | |
| first.globalAlpha = opacity; | |
| first.drawImage(first_img, 0, 0); | |
| next.clearRect(0, 0, canvas.width, canvas.height); | |
| next.globalAlpha = 1 - opacity; | |
| next.drawImage(next_img, x, y); | |
| ctx.clearRect(0, 0, canvas.width, canvas.height); | |
| ctx.drawImage(first_canvas, 0, 0); | |
| ctx.drawImage(next_canvas, 0, 0); | |
| if (opacity <= 0) return done(); | |
| else requestAnimationFrame(fade); | |
| }; | |
| fade(); | |
| }); | |
| } | |
| </script> | |
| </body> | |
| </html> |
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