Rumah > Artikel > hujung hadapan web > canvas像素点操作之视频绿幕抠图
这篇文章主要介绍了canvas像素点操作之视频绿幕抠图的相关资料,小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧
本文介绍了canvas像素点操作之视频绿幕抠图,分享给大家,具体如下:
用法:
context.putImageData(imgData, x, y, dX, dY, dWidth, dHeight);
下面的栗子简单实现了几个简单的滤镜效果,具体算法参考的这里,学过《数字图像处理》的同学应该对此理解更深刻。
demo
该栗子纯属为了演示功能而做,如果只强调效果而不在乎数据的话,用CSS3的filter属性便能高效又轻松地搞定。
部分代码
import imgUrl from './component/sample.jpg'; export default { data () { return { imgUrl: imgUrl } }, methods: { onOperate1 () { this.ctx.putImageData(this.onCompute1(), 0, 0); }, onOperate2 () { this.ctx.putImageData(this.onCompute2(), 0, 0); }, ... onCancel () { this.reload(); }, onCompute1 () { let data = this.frameData.data; for (let i = 0; i < this.imgDataLength; i += 4) { let r = data[i + 0], g = data[i + 1], b = data[i + 2]; data[i + 0] = 255 - r; data[i + 1] = 255 - g; data[i + 2] = 255 - b; } return this.frameData; }, onCompute2 () { let data = this.frameData.data; for (let i = 0; i < this.imgDataLength; i += 4) { data[i] = Math.abs(data[i + 1] - data[i + 2] + data[i + 1] + data[i]) * data[i] / 256; data[i + 1] = Math.abs(data[i + 2] - data[i + 1] + data[i + 2] + data[i]) * data[i] / 256; data[i + 2] = Math.abs(data[i + 2] - data[i + 1] + data[i + 2] + data[i]) * data[i + 1] / 256; } return this.frameData; }, ... }, mounted () { this.canvas = this.$refs['canvas']; this.ctx = this.canvas.getContext('2d'); this.reload(); } }
上周跟同学去了一趟溧阳天目湖的南山竹海,在景区被忽悠拍了一张照片,就是这张 ——
然后被朋友圈吐槽抠图。其实当时就是站在一块绿幕前拍的:joy: 。
PS中魔法棒工具可以把图片中一定容差下的相近像素都选中、清空,轻松做到一键“抠图”,前提是主体一定要与背景有大的差异,即像素值差值越大,抠图效果越好。
Canvas同样可以做到,并且可以处理视频帧,其中的原理是一样的 —— 将每个视频帧中绿幕的像素块透明度置0即可。像这样 ——
demo
部分代码
import videoUrl from './component/video.ogv'; import imgUrl from './component/sample.jpg'; const TOLERANCE = 5; export default { data () { return { videoUrl: videoUrl, imgUrl: imgUrl } }, methods: { draw () { if (this.video.paused || this.video.ended) { return; } this.ctx.drawImage(this.video, 0, 0, this.width, this.height); this.ctx.putImageData(this.cutOut(), 0, 0); }, cutOut () { let frameData = this.ctx.getImageData(0, 0, this.width, this.height), len = frameData.data.length / 4; for (let i = 0; i < len; i++) { let r = frameData.data[i * 4 + 0], g = frameData.data[i * 4 + 1], b = frameData.data[i * 4 + 2]; if (r - 100 >= TOLERANCE && g - 100 >= TOLERANCE && b - 43 <= TOLERANCE) { frameData.data[i * 4 + 3] = 0; } } return frameData; } }, mounted () { this.video = this.$refs['video']; this.canvas = this.$refs['canvas']; this.ctx = this.canvas.getContext('2d'); this.timer = null; this.video.addEventListener('play', () => { this.width = this.video.videoWidth; this.height = this.video.videoHeight; this.timer && clearInterval(this.timer); this.timer = setInterval(() => { this.draw(); }, 50); }, false); } }
参考资料
Manipulating video using canvas
Pixel manipulation with canvas
Canvas and images and pixels
总结:以上就是本篇文的全部内容,希望能对大家的学习有所帮助。更多相关教程请访问Html5视频教程!
相关推荐:
Atas ialah kandungan terperinci canvas像素点操作之视频绿幕抠图. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!