javascript使用H5新版媒體接口navigator.mediaDevices.getUserMedia，作掃描二維碼，並識別內容

本文代碼測試要求，最新的chrome瀏覽器(手機APP)，而且要容許chrome拍照錄像權限，必需要HTTPS協議，http不支持。

原理：調用攝像頭，將攝像頭返回的媒體流渲染到視頻標籤中，再經過canvas繪製到畫布上面，最後經過canvas分析二維碼

兼容性只在手機中的chrome中測試經過，微信裏面也能使用，可是canvas繪圖很卡

測試鏈接

 

引用了第三方的qrcode.js解碼，可是這個文件並未在GitHub中找到，不知道出處。源碼：

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d=i-(h-i);if(d<0){e=i/(i-d);d=0}else{if(d>=qrcode.width){e=(qrcode.width-1-i)/(d-i);d=qrcode.width-1}}var c=Math.floor(g-(f-g)*e);e=1;if(c<0){e=g/(g-c);c=0}else{if(c>=qrcode.height){e=(qrcode.height-1-g)/(c-g);c=qrcode.height-1}}d=Math.floor(i+(d-i)*e);b+=this._bi(i,g,d,c);return b-1};this._bj=function(c,d){var b=this._bh(Math.floor(c.X),Math.floor(c.Y),Math.floor(d.X),Math.floor(d.Y));var e=this._bh(Math.floor(d.X),Math.floor(d.Y),Math.floor(c.X),Math.floor(c.Y));if(isNaN(b)){return e/7}if(isNaN(e)){return b/7}return(b+e)/14};this._bk=function(d,c,b){return(this._bj(d,c)+this._bj(d,b))/2};this.distance=function(c,b){xDiff=c.X-b.X;yDiff=c.Y-b.Y;return Math.sqrt((xDiff*xDiff+yDiff*yDiff))};this._bx=function(g,f,d,e){var b=Math.round(this.distance(g,f)/e);var c=Math.round(this.distance(g,d)/e);var h=((b+c)>>1)+7;switch(h&3){case 0:h++;break;case 2:h--;break;case 3:throw"Error"}return h};this._bl=function(g,f,d,j){var k=Math.floor(j*g);var h=Math.max(0,f-k);var i=Math.min(qrcode.width-1,f+k);if(i-h<g*3){throw"Error"}var b=Math.max(0,d-k);var c=Math.min(qrcode.height-1,d+k);var e=new _ak(this.image,h,b,i-h,c-b,g,this._am);return e.find()};this.createTransform=function(l,h,k,b,g){var j=g-3.5;var i;var f;var e;var c;if(b!=null){i=b.X;f=b.Y;e=c=j-3}else{i=(h.X-l.X)+k.X;f=(h.Y-l.Y)+k.Y;e=c=j}var d=_ae._ag(3.5,3.5,j,3.5,e,c,3.5,j,l.X,l.Y,h.X,h.Y,i,f,k.X,k.Y);return d};this._bz=function(e,b,d){var c=_aa;return c._af(e,d,b)};this._cd=function(r){var j=r._gq;var h=r._gs;var n=r._gp;var d=this._bk(j,h,n);if(d<1){throw"Error"}var s=this._bx(j,h,n,d);var b=_a3._at(s);var k=b._cr-7;var l=null;if(b._as.length>0){var f=h.X-j.X+n.X;var e=h.Y-j.Y+n.Y;var c=1-3/k;var u=Math.floor(j.X+c*(f-j.X));var t=Math.floor(j.Y+c*(e-j.Y));for(var q=4;q<=16;q<<=1){l=this._bl(d,u,t,q);break}}var g=this.createTransform(j,h,n,l,s);var m=this._bz(this.image,g,s);var o;if(l==null){o=new Array(n,j,h)}else{o=new Array(n,j,h,l)}return new _bg(m,o)};this.detect=function(){var b=new _cc()._ce(this.image);return this._cd(b)}}var _ca=21522;var _cb=new Array(new Array(21522,0),new Array(20773,1),new Array(24188,2),new Array(23371,3),new Array(17913,4),new Array(16590,5),new Array(20375,6),new Array(19104,7),new Array(30660,8),new Array(29427,9),new Array(32170,10),new Array(30877,11),new Array(26159,12),new Array(25368,13),new Array(27713,14),new Array(26998,15),new Array(5769,16),new Array(5054,17),new Array(7399,18),new Array(6608,19),new Array(1890,20),new Array(597,21),new Array(3340,22),new Array(2107,23),new Array(13663,24),new Array(12392,25),new Array(16177,26),new Array(14854,27),new Array(9396,28),new Array(8579,29),new Array(11994,30),new Array(11245,31));var _ch=new Array(0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4);function _ax(a){this._cf=_cg.forBits((a>>3)&3);this._fe=(a&7);this.__defineGetter__("_cg",function(){return this._cf});this.__defineGetter__("_dx",function(){return this._fe});this.GetHashCode=function(){return(this._cf.ordinal()<<3)|_fe};this.Equals=function(c){var b=c;return this._cf==b._cf&&this._fe==b._fe}}_ax._gj=function(d,c){d^=c;return _ch[d&15]+_ch[(_ew(d,4)&15)]+_ch[(_ew(d,8)&15)]+_ch[(_ew(d,12)&15)]+_ch[(_ew(d,16)&15)]+_ch[(_ew(d,20)&15)]+_ch[(_ew(d,24)&15)]+_ch[(_ew(d,28)&15)]};_ax._ci=function(a){var b=_ax._cj(a);if(b!=null){return b}return _ax._cj(a^_ca)};_ax._cj=function(d){var b=4294967295;var a=0;for(var c=0;c<_cb.length;c++){var g=_cb[c];var f=g[0];if(f==d){return new _ax(g[1])}var e=this._gj(d,f);if(e<b){a=g[1];b=e}}if(b<=3){return new _ax(a)}return null};function _cg(a,c,b){this._ff=a;this.bits=c;this.name=b;this.__defineGetter__("Bits",function(){return this.bits});this.__defineGetter__("Name",function(){return this.name});this.ordinal=function(){return this._ff}}_cg.forBits=function(a){if(a<0||a>=FOR_BITS.length){throw"bad arguments"}return FOR_BITS[a]};var L=new _cg(0,1,"L");var M=new _cg(1,0,"M");var Q=new _cg(2,3,"Q");var H=new _cg(3,2,"H");var FOR_BITS=new Array(M,L,H,Q);function _ac(d,a){if(!a){a=d}if(d<1||a<1){throw"Both dimensions must be greater than 0"}this.width=d;this.height=a;var c=d>>5;if((d&31)!=0){c++}this.rowSize=c;this.bits=new Array(c*a);for(var b=0;b<this.bits.length;b++){this.bits[b]=0}this.__defineGetter__("Width",function(){return this.width});this.__defineGetter__("Height",function(){return this.height});this.__defineGetter__("Dimension",function(){if(this.width!=this.height){throw"Can't call getDimension() on a non-square matrix"}return this.width});this._ds=function(e,g){var f=g*this.rowSize+(e>>5);return((_ew(this.bits[f],(e&31)))&1)!=0};this._dq=function(e,g){var f=g*this.rowSize+(e>>5);this.bits[f]|=1<<(e&31)};this.flip=function(e,g){var f=g*this.rowSize+(e>>5);this.bits[f]^=1<<(e&31)};this.clear=function(){var e=this.bits.length;for(var f=0;f<e;f++){this.bits[f]=0}};this._bq=function(g,j,f,m){if(j<0||g<0){throw"Left and top must be nonnegative"}if(m<1||f<1){throw"Height and width must be at least 1"}var l=g+f;var e=j+m;if(e>this.height||l>this.width){throw"The region must fit inside the matrix"}for(var i=j;i<e;i++){var h=i*this.rowSize;for(var k=g;k<l;k++){this.bits[h+(k>>5)]|=1<<(k&31)}}}}function _dl(a,b){this._dv=a;this._dw=b;this.__defineGetter__("_du",function(){return this._dv});this.__defineGetter__("Codewords",function(){return this._dw})}_dl._gn=function(c,h,s){if(c.length!=h._dp){throw"bad arguments"}var k=h._bu(s);var e=0;var d=k._fb();for(var r=0;r<d.length;r++){e+=d[r].Count}var l=new Array(e);var n=0;for(var o=0;o<d.length;o++){var f=d[o];for(var r=0;r<f.Count;r++){var m=f._dm;var t=k._bo+m;l[n++]=new _dl(m,new Array(t))}}var u=l[0]._dw.length;var b=l.length-1;while(b>=0){var w=l[b]._dw.length;if(w==u){break}b--}b++;var g=u-k._bo;var a=0;for(var r=0;r<g;r++){for(var o=0;o<n;o++){l[o]._dw[r]=c[a++]}}for(var o=b;o<n;o++){l[o]._dw[g]=c[a++]}var q=l[0]._dw.length;for(var r=g;r<q;r++){for(var o=0;o<n;o++){var v=o<b?r:r+1;l[o]._dw[v]=c[a++]}}return l};function _cl(a){var b=a.Dimension;if(b<21||(b&3)!=1){throw"Error _cl"}this._au=a;this._cp=null;this._co=null;this._dk=function(d,c,e){return this._au._ds(d,c)?(e<<1)|1:e<<1};this._cm=function(){if(this._co!=null){return this._co}var g=0;for(var e=0;e<6;e++){g=this._dk(e,8,g)}g=this._dk(7,8,g);g=this._dk(8,8,g);g=this._dk(8,7,g);for(var c=5;c>=0;c--){g=this._dk(8,c,g)}this._co=_ax._ci(g);if(this._co!=null){return this._co}var f=this._au.Dimension;g=0;var d=f-8;for(var e=f-1;e>=d;e--){g=this._dk(e,8,g)}for(var c=f-7;c<f;c++){g=this._dk(8,c,g)}this._co=_ax._ci(g);if(this._co!=null){return this._co}throw"Error _cm"};this._cq=function(){if(this._cp!=null){return this._cp}var h=this._au.Dimension;var f=(h-17)>>2;if(f<=6){return _a3._av(f)}var g=0;var e=h-11;for(var c=5;c>=0;c--){for(var d=h-9;d>=e;d--){g=this._dk(d,c,g)}}this._cp=_a3._aw(g);if(this._cp!=null&&this._cp._cr==h){return this._cp}g=0;for(var d=5;d>=0;d--){for(var c=h-9;c>=e;c--){g=this._dk(d,c,g)}}this._cp=_a3._aw(g);if(this._cp!=null&&this._cp._cr==h){return this._cp}throw"Error _cq"};this._gk=function(){var r=this._cm();var o=this._cq();var c=_dx._gl(r._dx);var f=this._au.Dimension;c._dj(this._au,f);var k=o._aq();var n=true;var s=new Array(o._dp);var m=0;var q=0;var h=0;for(var e=f-1;e>0;e-=2){if(e==6){e--}for(var l=0;l<f;l++){var g=n?f-1-l:l;for(var d=0;d<2;d++){if(!k._ds(e-d,g)){h++;q<<=1;if(this._au._ds(e-d,g)){q|=1}if(h==8){s[m++]=q;h=0;q=0}}}}n^=true}if(m!=o._dp){throw"Error _gk"}return s}}_dx={};_dx._gl=function(a){if(a<0||a>7){throw"bad arguments"}return _dx._dy[a]};function _fg(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(b,a){return((b+a)&1)==0}}function _fh(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(b,a){return(b&1)==0}}function _fi(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(b,a){return a%3==0}}function _fj(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(b,a){return(b+a)%3==0}}function _fk(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(b,a){return(((_ew(b,1))+(a/3))&1)==0}}function _fl(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(c,b){var a=c*b;return(a&1)+(a%3)==0}}function _fm(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(c,b){var a=c*b;return(((a&1)+(a%3))&1)==0}}function _fn(){this._dj=function(c,d){for(var b=0;b<d;b++){for(var a=0;a<d;a++){if(this._fw(b,a)){c.flip(a,b)}}}};this._fw=function(b,a){return((((b+a)&1)+((b*a)%3))&1)==0}}_dx._dy=new Array(new _fg(),new _fh(),new _fi(),new _fj(),new _fk(),new _fl(),new _fm(),new _fn());function _db(_fa){this._fa=_fa;this.decode=function(received,_fv){var poly=new _bp(this._fa,received);var _dh=new Array(_fv);for(var i=0;i<_dh.length;i++){_dh[i]=0}var _fq=false;var noError=true;for(var i=0;i<_fv;i++){var eval=poly.evaluateAt(this._fa.exp(_fq?i+1:i));_dh[_dh.length-1-i]=eval;if(eval!=0){noError=false}}if(noError){return}var _fu=new _bp(this._fa,_dh);var _dg=this._eb(this._fa._ba(_fv,1),_fu,_fv);var sigma=_dg[0];var omega=_dg[1];var _dz=this._ey(sigma);var _ea=this._di(omega,_dz,_fq);for(var i=0;i<_dz.length;i++){var position=received.length-1-this._fa.log(_dz[i]);if(position<0){throw"ReedSolomonException Bad error location"}received[position]=_az._bd(received[position],_ea[i])}};this._eb=function(a,b,R){if(a._ec<b._ec){var temp=a;a=b;b=temp}var rLast=a;var r=b;var sLast=this._fa.One;var s=this._fa.Zero;var tLast=this._fa.Zero;var t=this._fa.One;while(r._ec>=Math.floor(R/2)){var rLastLast=rLast;var _ga=sLast;var _gb=tLast;rLast=r;sLast=s;tLast=t;if(rLast.Zero){throw"r_{i-1} was zero"}r=rLastLast;var q=this._fa.Zero;var _df=rLast._ex(rLast._ec);var _fy=this._fa.inverse(_df);while(r._ec>=rLast._ec&&!r.Zero){var _fx=r._ec-rLast._ec;var scale=this._fa.multiply(r._ex(r._ec),_fy);q=q._bd(this._fa._ba(_fx,scale));r=r._bd(rLast._dc(_fx,scale))}s=q.multiply1(sLast)._bd(_ga);t=q.multiply1(tLast)._bd(_gb)}var _de=t._ex(0);if(_de==0){throw"ReedSolomonException sigmaTilde(0) was zero"}var inverse=this._fa.inverse(_de);var sigma=t.multiply2(inverse);var omega=r.multiply2(inverse);return new Array(sigma,omega)};this._ey=function(_ez){var _fz=_ez._ec;if(_fz==1){return new Array(_ez._ex(1))}var result=new Array(_fz);var e=0;for(var i=1;i<256&&e<_fz;i++){if(_ez.evaluateAt(i)==0){result[e]=this._fa.inverse(i);e++}}if(e!=_fz){throw"Error locator degree does not match number of roots"}return result};this._di=function(_fs,_dz,_fq){var s=_dz.length;var result=new Array(s);for(var i=0;i<s;i++){var _gc=this._fa.inverse(_dz[i]);var _dr=1;for(var j=0;j<s;j++){if(i!=j){_dr=this._fa.multiply(_dr,_az._bd(1,this._fa.multiply(_dz[j],_gc)))}}result[i]=this._fa.multiply(_fs.evaluateAt(_gc),this._fa.inverse(_dr));if(_fq){result[i]=this._fa.multiply(result[i],_gc)}}return result}}function _bp(f,e){if(e==null||e.length==0){throw"bad arguments"}this._fa=f;var c=e.length;if(c>1&&e[0]==0){var d=1;while(d<c&&e[d]==0){d++}if(d==c){this._dd=f.Zero._dd}else{this._dd=new Array(c-d);for(var b=0;b<this._dd.length;b++){this._dd[b]=0}for(var a=0;a<this._dd.length;a++){this._dd[a]=e[d+a]}}}else{this._dd=e}this.__defineGetter__("Zero",function(){return this._dd[0]==0});this.__defineGetter__("_ec",function(){return this._dd.length-1});this.__defineGetter__("Coefficients",function(){return this._dd});this._ex=function(g){return this._dd[this._dd.length-1-g]};this.evaluateAt=function(h){if(h==0){return this._ex(0)}var l=this._dd.length;if(h==1){var g=0;for(var k=0;k<l;k++){g=_az._bd(g,this._dd[k])}return g}var j=this._dd[0];for(var k=1;k<l;k++){j=_az._bd(this._fa.multiply(h,j),this._dd[k])}return j};this._bd=function(g){if(this._fa!=g._fa){throw"GF256Polys do not have same _az _fa"}if(this.Zero){return g}if(g.Zero){return this}var o=this._dd;var n=g._dd;if(o.length>n.length){var j=o;o=n;n=j}var h=new Array(n.length);var k=n.length-o.length;for(var m=0;m<k;m++){h[m]=n[m]}for(var l=k;l<n.length;l++){h[l]=_az._bd(o[l-k],n[l])}return new _bp(f,h)};this.multiply1=function(o){if(this._fa!=o._fa){throw"GF256Polys do not have same _az _fa"}if(this.Zero||o.Zero){return this._fa.Zero}var r=this._dd;var g=r.length;var l=o._dd;var n=l.length;var q=new Array(g+n-1);for(var m=0;m<g;m++){var h=r[m];for(var k=0;k<n;k++){q[m+k]=_az._bd(q[m+k],this._fa.multiply(h,l[k]))}}return new _bp(this._fa,q)};this.multiply2=function(g){if(g==0){return this._fa.Zero}if(g==1){return this}var j=this._dd.length;var k=new Array(j);for(var h=0;h<j;h++){k[h]=this._fa.multiply(this._dd[h],g)}return new _bp(this._fa,k)};this._dc=function(l,g){if(l<0){throw"bad arguments"}if(g==0){return this._fa.Zero}var j=this._dd.length;var k=new Array(j+l);for(var h=0;h<k.length;h++){k[h]=0}for(var h=0;h<j;h++){k[h]=this._fa.multiply(this._dd[h],g)}return new _bp(this._fa,k)};this.divide=function(l){if(this._fa!=l._fa){throw"GF256Polys do not have same _az _fa"}if(l.Zero){throw"Divide by 0"}var j=this._fa.Zero;var o=this;var g=l._ex(l._ec);var n=this._fa.inverse(g);while(o._ec>=l._ec&&!o.Zero){var m=o._ec-l._ec;var h=this._fa.multiply(o._ex(o._ec),n);var i=l._dc(m,h);var k=this._fa._ba(m,h);j=j._bd(k);o=o._bd(i)}return new Array(j,o)}}function _az(b){this._gh=new Array(256);this._gi=new Array(256);var a=1;for(var e=0;e<256;e++){this._gh[e]=a;a<<=1;if(a>=256){a^=b}}for(var e=0;e<255;e++){this._gi[this._gh[e]]=e}var d=new Array(1);d[0]=0;this.zero=new _bp(this,new Array(d));var c=new Array(1);c[0]=1;this.one=new _bp(this,new Array(c));this.__defineGetter__("Zero",function(){return this.zero});this.__defineGetter__("One",function(){return this.one});this._ba=function(j,f){if(j<0){throw"bad arguments"}if(f==0){return zero}var h=new Array(j+1);for(var g=0;g<h.length;g++){h[g]=0}h[0]=f;return new _bp(this,h)};this.exp=function(f){return this._gh[f]};this.log=function(f){if(f==0){throw"bad arguments"}return this._gi[f]};this.inverse=function(f){if(f==0){throw"System.ArithmeticException"}return this._gh[255-this._gi[f]]};this.multiply=function(g,f){if(g==0||f==0){return 0}if(g==1){return f}if(f==1){return g}return this._gh[(this._gi[g]+this._gi[f])%255]}}_az._bb=new _az(285);_az._bc=new _az(301);_az._bd=function(d,c){return d^c};Decoder={};Decoder.rsDecoder=new _db(_az._bb);Decoder.correctErrors=function(g,b){var d=g.length;var f=new Array(d);for(var e=0;e<d;e++){f[e]=g[e]&255}var a=g.length-b;try{Decoder.rsDecoder.decode(f,a)}catch(c){throw c}for(var e=0;e<b;e++){g[e]=f[e]}};Decoder.decode=function(r){var b=new _cl(r);var o=b._cq();var c=b._cm()._cg;var q=b._gk();var a=_dl._gn(q,o,c);var f=0;for(var k=0;k<a.length;k++){f+=a[k]._du}var e=new Array(f);var n=0;for(var h=0;h<a.length;h++){var m=a[h];var d=m.Codewords;var g=m._du;Decoder.correctErrors(d,g);for(var k=0;k<g;k++){e[n++]=d[k]}}var l=new QRCodeDataBlockReader(e,o._fd,c.Bits);return l};qrcode={};qrcode.imagedata=null;qrcode.width=0;qrcode.height=0;qrcode.qrCodeSymbol=null;qrcode.debug=false;qrcode.maxImgSize=1024*1024;qrcode._eo=[[10,9,8,8],[12,11,16,10],[14,13,16,12]];qrcode.callback=null;qrcode.decode=function(d){if(arguments.length==0){var b=document.getElementById("qr-canvas");var a=b.getContext("2d");qrcode.width=b.width;qrcode.height=b.height;qrcode.imagedata=a.getImageData(0,0,qrcode.width,qrcode.height);qrcode.result=qrcode.process(a);if(qrcode.callback!=null){qrcode.callback(qrcode.result)}return qrcode.result}else{var c=new Image();c.onload=function(){var g=document.getElementById("out-canvas");if(g!=null){var j=g.getContext("2d");j.clearRect(0,0,320,240);j.drawImage(c,0,0,320,240)}var i=document.createElement("canvas");var h=i.getContext("2d");var f=c.height;var l=c.width;if(c.width*c.height>qrcode.maxImgSize){var k=c.width/c.height;f=Math.sqrt(qrcode.maxImgSize/k);l=k*f}i.width=l;i.height=f;h.drawImage(c,0,0,i.width,i.height);qrcode.width=i.width;qrcode.height=i.height;try{qrcode.imagedata=h.getImageData(0,0,i.width,i.height)}catch(m){qrcode.result="Cross domain image reading not supported in your browser! Save it to your computer then drag and drop the file!";if(qrcode.callback!=null){qrcode.callback(qrcode.result)}return}try{qrcode.result=qrcode.process(h)}catch(m){console.log(m);qrcode.result="error decoding QR Code"}if(qrcode.callback!=null){qrcode.callback(qrcode.result)}};c.src=d}};qrcode.isUrl=function(a){var b=/(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/;return b.test(a)};qrcode.decode_url=function(b){var d="";try{d=escape(b)}catch(c){console.log(c);d=b}var a="";try{a=decodeURIComponent(d)}catch(c){console.log(c);a=d}return a};qrcode.decode_utf8=function(a){if(qrcode.isUrl(a)){return qrcode.decode_url(a)}else{return a}};qrcode.process=function(r){var a=new Date().getTime();var c=qrcode.grayScaleToBitmap(qrcode.grayscale());if(qrcode.debug){for(var m=0;m<qrcode.height;m++){for(var n=0;n<qrcode.width;n++){var o=(n*4)+(m*qrcode.width*4);qrcode.imagedata.data[o]=c[n+m*qrcode.width]?0:0;qrcode.imagedata.data[o+1]=c[n+m*qrcode.width]?0:0;qrcode.imagedata.data[o+2]=c[n+m*qrcode.width]?255:0}}r.putImageData(qrcode.imagedata,0,0)}var h=new Detector(c);var q=h.detect();if(qrcode.debug){r.putImageData(qrcode.imagedata,0,0)}var k=Decoder.decode(q.bits);var g=k.DataByte;var l="";for(var f=0;f<g.length;f++){for(var e=0;e<g[f].length;e++){l+=String.fromCharCode(g[f][e])}}var d=new Date().getTime();var b=d-a;console.log(b);return qrcode.decode_utf8(l)};qrcode.getPixel=function(a,b){if(qrcode.width<a){throw"point error"}if(qrcode.height<b){throw"point error"}point=(a*4)+(b*qrcode.width*4);p=(qrcode.imagedata.data[point]*33+qrcode.imagedata.data[point+1]*34+qrcode.imagedata.data[point+2]*33)/100;return p};qrcode.binarize=function(d){var c=new Array(qrcode.width*qrcode.height);for(var e=0;e<qrcode.height;e++){for(var b=0;b<qrcode.width;b++){var a=qrcode.getPixel(b,e);c[b+e*qrcode.width]=a<=d?true:false}}return c};qrcode._em=function(d){var c=4;var k=Math.floor(qrcode.width/c);var j=Math.floor(qrcode.height/c);var f=new Array(c);for(var g=0;g<c;g++){f[g]=new Array(c);for(var e=0;e<c;e++){f[g][e]=new Array(0,0)}}for(var o=0;o<c;o++){for(var a=0;a<c;a++){f[a][o][0]=255;for(var l=0;l<j;l++){for(var n=0;n<k;n++){var h=d[k*a+n+(j*o+l)*qrcode.width];if(h<f[a][o][0]){f[a][o][0]=h}if(h>f[a][o][1]){f[a][o][1]=h}}}}}var m=new Array(c);for(var b=0;b<c;b++){m[b]=new Array(c)}for(var o=0;o<c;o++){for(var a=0;a<c;a++){m[a][o]=Math.floor((f[a][o][0]+f[a][o][1])/2)}}return m};qrcode.grayScaleToBitmap=function(f){var j=qrcode._em(f);var b=j.length;var e=Math.floor(qrcode.width/b);var d=Math.floor(qrcode.height/b);var c=new Array(qrcode.height*qrcode.width);for(var i=0;i<b;i++){for(var a=0;a<b;a++){for(var g=0;g<d;g++){for(var h=0;h<e;h++){c[e*a+h+(d*i+g)*qrcode.width]=(f[e*a+h+(d*i+g)*qrcode.width]<j[a][i])?true:false}}}}return c};qrcode.grayscale=function(){var c=new Array(qrcode.width*qrcode.height);for(var d=0;d<qrcode.height;d++){for(var b=0;b<qrcode.width;b++){var a=qrcode.getPixel(b,d);c[b+d*qrcode.width]=a}}return c};function _ew(a,b){if(a>=0){return a>>b}else{return(a>>b)+(2<<~b)}}Array.prototype.remove=function(c,b){var a=this.slice((b||c)+1||this.length);this.length=c<0?this.length+c:c;return this.push.apply(this,a)};var _gf=3;var _eh=57;var _el=8;var _eg=2;qrcode._er=function(c){function b(l,k){xDiff=l.X-k.X;yDiff=l.Y-k.Y;return Math.sqrt((xDiff*xDiff+yDiff*yDiff))}function d(k,o,n){var m=o.x;var l=o.y;return((n.x-m)*(k.y-l))-((n.y-l)*(k.x-m))}var i=b(c[0],c[1]);var f=b(c[1],c[2]);var e=b(c[0],c[2]);var a,j,h;if(f>=i&&f>=e){j=c[0];a=c[1];h=c[2]}else{if(e>=f&&e>=i){j=c[1];a=c[0];h=c[2]}else{j=c[2];a=c[0];h=c[1]}}if(d(a,j,h)<0){var g=a;a=h;h=g}c[0]=a;c[1]=j;c[2]=h};function _cz(c,a,b){this.x=c;this.y=a;this.count=1;this._aj=b;this.__defineGetter__("_ei",function(){return this._aj});this.__defineGetter__("Count",function(){return this.count});this.__defineGetter__("X",function(){return this.x});this.__defineGetter__("Y",function(){return this.y});this._ek=function(){this.count++};this._ev=function(f,e,d){if(Math.abs(e-this.y)<=f&&Math.abs(d-this.x)<=f){var g=Math.abs(f-this._aj);return g<=1||g/this._aj<=1}return false}}function _es(a){this._go=a[0];this._gu=a[1];this._gr=a[2];this.__defineGetter__("_gp",function(){return this._go});this.__defineGetter__("_gq",function(){return this._gu});this.__defineGetter__("_gs",function(){return this._gr})}function _cc(){this.image=null;this._cv=[];this._ge=false;this._al=new Array(0,0,0,0,0);this._am=null;this.__defineGetter__("_da",function(){this._al[0]=0;this._al[1]=0;this._al[2]=0;this._al[3]=0;this._al[4]=0;return this._al});this._ao=function(f){var b=0;for(var d=0;d<5;d++){var e=f[d];if(e==0){return false}b+=e}if(b<7){return false}var c=Math.floor((b<<_el)/7);var a=Math.floor(c/2);return Math.abs(c-(f[0]<<_el))<a&&Math.abs(c-(f[1]<<_el))<a&&Math.abs(3*c-(f[2]<<_el))<3*a&&Math.abs(c-(f[3]<<_el))<a&&Math.abs(c-(f[4]<<_el))<a};this._an=function(b,a){return(a-b[4]-b[3])-b[2]/2};this._ap=function(a,j,d,g){var c=this.image;var h=qrcode.height;var b=this._da;var f=a;while(f>=0&&c[j+f*qrcode.width]){b[2]++;f--}if(f<0){return NaN}while(f>=0&&!c[j+f*qrcode.width]&&b[1]<=d){b[1]++;f--}if(f<0||b[1]>d){return NaN}while(f>=0&&c[j+f*qrcode.width]&&b[0]<=d){b[0]++;f--}if(b[0]>d){return NaN}f=a+1;while(f<h&&c[j+f*qrcode.width]){b[2]++;f++}if(f==h){return NaN}while(f<h&&!c[j+f*qrcode.width]&&b[3]<d){b[3]++;f++}if(f==h||b[3]>=d){return NaN}while(f<h&&c[j+f*qrcode.width]&&b[4]<d){b[4]++;f++}if(b[4]>=d){return NaN}var e=b[0]+b[1]+b[2]+b[3]+b[4];if(5*Math.abs(e-g)>=2*g){return NaN}return this._ao(b)?this._an(b,f):NaN};this._ej=function(b,a,e,h){var d=this.image;var i=qrcode.width;var c=this._da;var g=b;while(g>=0&&d[g+a*qrcode.width]){c[2]++;g--}if(g<0){return NaN}while(g>=0&&!d[g+a*qrcode.width]&&c[1]<=e){c[1]++;g--}if(g<0||c[1]>e){return NaN}while(g>=0&&d[g+a*qrcode.width]&&c[0]<=e){c[0]++;g--}if(c[0]>e){return NaN}g=b+1;while(g<i&&d[g+a*qrcode.width]){c[2]++;g++}if(g==i){return NaN}while(g<i&&!d[g+a*qrcode.width]&&c[3]<e){c[3]++;g++}if(g==i||c[3]>=e){return NaN}while(g<i&&d[g+a*qrcode.width]&&c[4]<e){c[4]++;g++}if(c[4]>=e){return NaN}var f=c[0]+c[1]+c[2]+c[3]+c[4];if(5*Math.abs(f-h)>=h){return NaN}return this._ao(c)?this._an(c,g):NaN};this._cu=function(c,f,e){var d=c[0]+c[1]+c[2]+c[3]+c[4];var n=this._an(c,e);var b=this._ap(f,Math.floor(n),c[2],d);if(!isNaN(b)){n=this._ej(Math.floor(n),Math.floor(b),c[2],d);if(!isNaN(n)){var l=d/7;var m=false;var h=this._cv.length;for(var g=0;g<h;g++){var a=this._cv[g];if(a._ev(l,b,n)){a._ek();m=true;break}}if(!m){var k=new _cz(n,b,l);this._cv.push(k);if(this._am!=null){this._am._ep(k)}}return true}}return false};this._ee=function(){var h=this._cv.length;if(h<3){throw"Couldn't find enough finder patterns"}if(h>3){var b=0;var j=0;for(var d=0;d<h;d++){var g=this._cv[d]._ei;b+=g;j+=(g*g)}var a=b/h;this._cv.sort(function(m,l){var k=Math.abs(l._ei-a);var i=Math.abs(m._ei-a);if(k<i){return(-1)}else{if(k==i){return 0}else{return 1}}});var e=Math.sqrt(j/h-a*a);var c=Math.max(0.2*a,e);for(var d=0;d<this._cv.length&&this._cv.length>3;d++){var f=this._cv[d];if(Math.abs(f._ei-a)>c){this._cv.remove(d);d--}}}if(this._cv.length>3){this._cv.sort(function(k,i){if(k.count>i.count){return -1}if(k.count<i.count){return 1}return 0})}return new Array(this._cv[0],this._cv[1],this._cv[2])};this._eq=function(){var b=this._cv.length;if(b<=1){return 0}var c=null;for(var d=0;d<b;d++){var a=this._cv[d];if(a.Count>=_eg){if(c==null){c=a}else{this._ge=true;return Math.floor((Math.abs(c.X-a.X)-Math.abs(c.Y-a.Y))/2)}}}return 0};this._cx=function(){var g=0;var c=0;var a=this._cv.length;for(var d=0;d<a;d++){var f=this._cv[d];if(f.Count>=_eg){g++;c+=f._ei}}if(g<3){return false}var e=c/a;var b=0;for(var d=0;d<a;d++){f=this._cv[d];b+=Math.abs(f._ei-e)}return b<=0.05*c};this._ce=function(e){var o=false;this.image=e;var n=qrcode.height;var k=qrcode.width;var a=Math.floor((3*n)/(4*_eh));if(a<_gf||o){a=_gf}var g=false;var d=new Array(5);for(var h=a-1;h<n&&!g;h+=a){d[0]=0;d[1]=0;d[2]=0;d[3]=0;d[4]=0;var b=0;for(var f=0;f<k;f++){if(e[f+h*qrcode.width]){if((b&1)==1){b++}d[b]++}else{if((b&1)==0){if(b==4){if(this._ao(d)){var c=this._cu(d,h,f);if(c){a=2;if(this._ge){g=this._cx()}else{var m=this._eq();if(m>d[2]){h+=m-d[2]-a;f=k-1}}}else{do{f++}while(f<k&&!e[f+h*qrcode.width]);f--}b=0;d[0]=0;d[1]=0;d[2]=0;d[3]=0;d[4]=0}else{d[0]=d[2];d[1]=d[3];d[2]=d[4];d[3]=1;d[4]=0;b=3}}else{d[++b]++}}else{d[b]++}}}if(this._ao(d)){var c=this._cu(d,h,k);if(c){a=d[0];if(this._ge){g=_cx()}}}}var l=this._ee();qrcode._er(l);return new _es(l)}}function _ai(c,a,b){this.x=c;this.y=a;this.count=1;this._aj=b;this.__defineGetter__("_ei",function(){return this._aj});this.__defineGetter__("Count",function(){return this.count});this.__defineGetter__("X",function(){return Math.floor(this.x)});this.__defineGetter__("Y",function(){return Math.floor(this.y)});this._ek=function(){this.count++};this._ev=function(f,e,d){if(Math.abs(e-this.y)<=f&&Math.abs(d-this.x)<=f){var g=Math.abs(f-this._aj);return g<=1||g/this._aj<=1}return false}}function _ak(g,c,b,f,a,e,d){this.image=g;this._cv=new Array();this.startX=c;this.startY=b;this.width=f;this.height=a;this._ef=e;this._al=new Array(0,0,0);this._am=d;this._an=function(i,h){return(h-i[2])-i[1]/2};this._ao=function(l){var k=this._ef;var h=k/2;for(var j=0;j<3;j++){if(Math.abs(k-l[j])>=h){return false}}return true};this._ap=function(h,r,l,o){var k=this.image;var q=qrcode.height;var j=this._al;j[0]=0;j[1]=0;j[2]=0;var n=h;while(n>=0&&k[r+n*qrcode.width]&&j[1]<=l){j[1]++;n--}if(n<0||j[1]>l){return NaN}while(n>=0&&!k[r+n*qrcode.width]&&j[0]<=l){j[0]++;n--}if(j[0]>l){return NaN}n=h+1;while(n<q&&k[r+n*qrcode.width]&&j[1]<=l){j[1]++;n++}if(n==q||j[1]>l){return NaN}while(n<q&&!k[r+n*qrcode.width]&&j[2]<=l){j[2]++;n++}if(j[2]>l){return NaN}var m=j[0]+j[1]+j[2];if(5*Math.abs(m-o)>=2*o){return NaN}return this._ao(j)?this._an(j,n):NaN};this._cu=function(l,o,n){var m=l[0]+l[1]+l[2];var u=this._an(l,n);var k=this._ap(o,Math.floor(u),2*l[1],m);if(!isNaN(k)){var t=(l[0]+l[1]+l[2])/3;var r=this._cv.length;for(var q=0;q<r;q++){var h=this._cv[q];if(h._ev(t,k,u)){return new _ai(u,k,t)}}var s=new _ai(u,k,t);this._cv.push(s);if(this._am!=null){this._am._ep(s)}}return null};this.find=function(){var q=this.startX;var t=this.height;var r=q+f;var s=b+(t>>1);var m=new Array(0,0,0);for(var k=0;k<t;k++){var o=s+((k&1)==0?((k+1)>>1):-((k+1)>>1));m[0]=0;m[1]=0;m[2]=0;var n=q;while(n<r&&!g[n+qrcode.width*o]){n++}var h=0;while(n<r){if(g[n+o*qrcode.width]){if(h==1){m[h]++}else{if(h==2){if(this._ao(m)){var l=this._cu(m,o,n);if(l!=null){return l}}m[0]=m[2];m[1]=1;m[2]=0;h=1}else{m[++h]++}}}else{if(h==1){h++}m[h]++}n++}if(this._ao(m)){var l=this._cu(m,o,r);if(l!=null){return l}}}if(!(this._cv.length==0)){return this._cv[0]}throw"Couldn't find enough alignment patterns"}}function QRCodeDataBlockReader(c,a,b){this._ed=0;this._cw=7;this.dataLength=0;this.blocks=c;this._en=b;if(a<=9){this.dataLengthMode=0}else{if(a>=10&&a<=26){this.dataLengthMode=1}else{if(a>=27&&a<=40){this.dataLengthMode=2}}}this._gd=function(f){var k=0;if(f<this._cw+1){var m=0;for(var e=0;e<f;e++){m+=(1<<e)}m<<=(this._cw-f+1);k=(this.blocks[this._ed]&m)>>(this._cw-f+1);this._cw-=f;return k}else{if(f<this._cw+1+8){var j=0;for(var e=0;e<this._cw+1;e++){j+=(1<<e)}k=(this.blocks[this._ed]&j)<<(f-(this._cw+1));this._ed++;k+=((this.blocks[this._ed])>>(8-(f-(this._cw+1))));this._cw=this._cw-f%8;if(this._cw<0){this._cw=8+this._cw}return k}else{if(f<this._cw+1+16){var j=0;var h=0;for(var e=0;e<this._cw+1;e++){j+=(1<<e)}var g=(this.blocks[this._ed]&j)<<(f-(this._cw+1));this._ed++;var d=this.blocks[this._ed]<<(f-(this._cw+1+8));this._ed++;for(var e=0;e<f-(this._cw+1+8);e++){h+=(1<<e)}h<<=8-(f-(this._cw+1+8));var l=(this.blocks[this._ed]&h)>>(8-(f-(this._cw+1+8)));k=g+d+l;this._cw=this._cw-(f-8)%8;if(this._cw<0){this._cw=8+this._cw}return k}else{return 0}}}};this.NextMode=function(){if((this._ed>this.blocks.length-this._en-2)){return 0}else{return this._gd(4)}};this.getDataLength=function(d){var e=0;while(true){if((d>>e)==1){break}e++}return this._gd(qrcode._eo[this.dataLengthMode][e])};this.getRomanAndFigureString=function(h){var f=h;var g=0;var j="";var d=new Array("0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"," ","$","%","*","+","-",".","/",":");do{if(f>1){g=this._gd(11);var i=Math.floor(g/45);var e=g%45;j+=d[i];j+=d[e];f-=2}else{if(f==1){g=this._gd(6);j+=d[g];f-=1}}}while(f>0);return j};this.getFigureString=function(f){var d=f;var e=0;var g="";do{if(d>=3){e=this._gd(10);if(e<100){g+="0"}if(e<10){g+="0"}d-=3}else{if(d==2){e=this._gd(7);if(e<10){g+="0"}d-=2}else{if(d==1){e=this._gd(4);d-=1}}}g+=e}while(d>0);return g};this.get8bitByteArray=function(g){var e=g;var f=0;var d=new Array();do{f=this._gd(8);d.push(f);e--}while(e>0);return d};this.getKanjiString=function(j){var g=j;var i=0;var h="";do{i=_gd(13);var e=i%192;var f=i/192;var k=(f<<8)+e;var d=0;if(k+33088<=40956){d=k+33088}else{d=k+49472}h+=String.fromCharCode(d);g--}while(g>0);return h};this.__defineGetter__("DataByte",function(){var g=new Array();var e=1;var f=2;var d=4;var n=8;do{var k=this.NextMode();if(k==0){if(g.length>0){break}else{throw"Empty data block"}}if(k!=e&&k!=f&&k!=d&&k!=n){throw"Invalid mode: "+k+" in (block:"+this._ed+" bit:"+this._cw+")"}dataLength=this.getDataLength(k);if(dataLength<1){throw"Invalid data length: "+dataLength}switch(k){case e:var l=this.getFigureString(dataLength);var i=new Array(l.length);for(var h=0;h<l.length;h++){i[h]=l.charCodeAt(h)}g.push(i);break;case f:var l=this.getRomanAndFigureString(dataLength);var i=new Array(l.length);for(var h=0;h<l.length;h++){i[h]=l.charCodeAt(h)}g.push(i);break;case d:var m=this.get8bitByteArray(dataLength);g.push(m);break;case n:var l=this.getKanjiString(dataLength);g.push(l);break}}while(true);return g})};

View Code

 

整個頁面源碼：

  1 <html>
  2 
  3 <head>
  4   <meta charset="UTF-8">
  5   <meta name="viewport" content="width=device-width, initial-scale=1.0">
  6   <meta http-equiv="X-UA-Compatible" content="ie=edge">
  7   <title>js喚起攝像頭識別二維碼</title>
  8   <style>
  9     #scan {
 10       display: block;
 11     }
 12     #qr-canvas {
 13       max-width: 300px;
 14     }
 15   </style>
 16 </head>
 17 
 18 <body>
 19   <div><a href="/" target="_blank">本站首頁</a></div>
 20   <hr>
 21   <div>兼容性只在手機中的chrome中測試經過，微信裏面也能使用，可是canvas繪圖很卡</div>
 22   <div>原理：調用攝像頭，將攝像頭返回的媒體流渲染到視頻標籤中，再經過canvas繪製到畫布上面，最後經過canvas分析二維碼</div>
 23   <hr>
 24   <a href="javascript:;" id="scan">掃碼</a>
 25   <div id="output"></div>
 26   <!-- 因爲llqrcode.js中寫死了id，因此id必須爲qr-canvas -->
 27   <canvas id="qr-canvas"></canvas>
 28   <video id="video" muted autoplay width="300" height="200"></video>
 29   <script src="https://cdn.bootcss.com/vConsole/3.2.0/vconsole.min.js"></script>
 30   <script>
 31     let vConsole = new VConsole();
 32   </script>
 33   <script type="text/javascript" src="llqrcode.js"></script>
 34   <script type="text/javascript">
 35 
 36     const Scan = {
 37       videoInputDevice: [],
 38       videoElement: document.getElementById("video"),
 39       canvasElement: document.getElementById("qr-canvas"),
 40       decodeTimer: null,
 41       canvasTimer: null,
 42       canvasContext: document.getElementById("qr-canvas").getContext("2d"),
 43       // 獲取到的媒體設備
 44       gotDevices (deviceInfos) {
 45         let that = this;
 46         for (let i = 0; i !== deviceInfos.length; ++i) {
 47           let deviceInfo = deviceInfos[i];
 48           if (deviceInfo.kind === 'audioinput') {
 49             // 音頻設備
 50           } else if (deviceInfo.kind === 'videoinput') {
 51             // 視頻設備
 52             that.videoInputDevice.push(deviceInfo);
 53           } else {
 54             // 其餘設備
 55             console.log('Found one other kind of source/device: ', deviceInfo);
 56           }
 57         }
 58       },
 59       getStream () {
 60         let that = this;
 61         if (window.stream) {
 62           window.stream.getTracks().forEach((track) => {
 63             track.stop();
 64           });
 65         }
 66 
 67         let constraints = {
 68           // 包含audio 可聲明音頻設備調用
 69           // 聲明視頻設備調用
 70           // video: true
 71           video: {
 72             deviceId: {
 73               // [1].deviceId 表示後置攝像頭,默認開啓的是前置攝像頭
 74               exact: that.videoInputDevice[1].deviceId
 75             }
 76           }
 77         };
 78 
 79         
 80         /* // 微信裏面此方法無效開啓後置攝像頭無效，必須使用 deviceId 開啓
 81         // 在chrome瀏覽器中可以使用此方法開啓後置攝像頭
 82         let front = false;
 83         let constraints = {
 84           video: {
 85             // environment表示後置攝像頭
 86             // user表示前置攝像頭
 87             facingMode: (front? "user" : "environment")
 88           }
 89         }; */
 90 
 91         // 視頻設備初始化
 92         navigator.mediaDevices.getUserMedia(constraints).then(that.gotStream.bind(that)).catch(that.handleError.bind(that));
 93         that.captureToCanvas();
 94         that.decode();
 95       },
 96 
 97       // 解碼
 98       decode () {
 99         let that = this;
100         try {
101           qrcode.decode();
102         } catch (e) {
103           console.log(e);
104         };
105         that.decodeTimer = setTimeout(that.decode.bind(that), 1000); // 解碼頻率爲1秒一次
106       },
107 
108       //將視頻流放到畫布
109       captureToCanvas () {
110         let that = this;
111         try {
112           // 根據視頻大小設置canvas大小
113           let w = that.videoElement.videoWidth;
114           let h = that.videoElement.videoHeight;
115           that.canvasElement.width = w;
116           that.canvasElement.height = h;
117           that.canvasContext.drawImage(that.videoElement, 0, 0, w, h);
118         } catch (e) {
119           console.log(e);
120         };
121         // 200毫秒繪製一次
122         that.canvasTimer = setTimeout(that.captureToCanvas.bind(that), 200);
123       },
124 
125       handleError (error) {
126         console.log('Error: ', error);
127       },
128 
129       gotStream (stream) {
130         let that = this;
131         window.stream = stream; // make stream available to console
132         that.videoElement.srcObject = stream;
133       },
134 
135       init () {
136         let that = this;
137         // API參考
138         // https://developer.mozilla.org/zh-CN/docs/Web/API/MediaDevices/enumerateDevices
139         // 先獲取設備列表，方便調用後置攝像頭
140         let devices = navigator.mediaDevices.enumerateDevices().then(that.gotDevices.bind(that));
141         document.querySelector('#scan').addEventListener('click', () => {
142           document.getElementById('output').innerHTML = '';
143           that.videoElement.style.display = 'block';
144           that.canvasElement.style.display = 'block';
145 
146           devices.then(that.getStream.bind(that)).catch(that.handleError.bind(that));
147 
148           that.canvasContext.clearRect(0, 0, 300, 200);
149           //結果回調
150           qrcode.callback = (e) => {
151             // 清除畫布，中止攝像頭
152             clearTimeout(that.decodeTimer);
153             clearTimeout(that.canvasTimer);
154             that.canvasContext.clearRect(0, 0, 300, 200);
155             if (window.stream) {
156               window.stream.getTracks().forEach((track) => {
157                 track.stop();
158               });
159             }
160             that.videoElement.style.display = 'none';
161             that.canvasElement.style.display = 'none';
162 
163             document.getElementById('output').innerHTML = '結果：' + e;
164           }
165         });
166       }
167     };
168     Scan.init();
169   </script>
170 </body>
171 
172 </html>