canvas像素点操作之视频绿幕抠图

context.putImageData(imgData, x, y, dX, dY, dWidth, dHeight);

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();
	}
}

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);
	}
}