javascript - how to animate drawing lines on canvas -

-

i have created lines connecting each other on canvas. want animate these lines while drawing on canvas.

can please help?

here code , fiddle url:

var c=document.getelementbyid("mycanvas"); var ctx=c.getcontext("2d"); ctx.moveto(0,0,0,0); ctx.lineto(300,100); ctx.stroke();  ctx.moveto(0,0,0,0); ctx.lineto(10,100); ctx.stroke();  ctx.moveto(10,100,0,0); ctx.lineto(80,200); ctx.stroke();  ctx.moveto(80,200,0,0); ctx.lineto(300,100); ctx.stroke();

http://jsfiddle.net/s4gwk/1/

i understand want lines extend incrementally along points in path using animation.

a demo: http://jsfiddle.net/m1erickson/7farq/

you can use function calculate waypoints along path:

// define path plot var vertices=[]; vertices.push({x:0,y:0}); vertices.push({x:300,y:100}); vertices.push({x:80,y:200}); vertices.push({x:10,y:100}); vertices.push({x:0,y:0});  // calc waypoints traveling along vertices function calcwaypoints(vertices){     var waypoints=[];     for(var i=1;i<vertices.length;i++){         var pt0=vertices[i-1];         var pt1=vertices[i];         var dx=pt1.x-pt0.x;         var dy=pt1.y-pt0.y;         for(var j=0;j<100;j++){             var x=pt0.x+dx*j/100;             var y=pt0.y+dy*j/100;             waypoints.push({x:x,y:y});         }     }     return(waypoints); }

then can use requestanimationframe animate each incremental line segment:

// calculate incremental points along path var points=calcwaypoints(vertices);   // variable hold how many frames have elapsed in animation // t represents each waypoint along path , incremented in animation loop var t=1;   // start animation animate();  // incrementally draw additional line segments along path function animate(){     if(t<points.length-1){ requestanimationframe(animate); }     // draw line segment last waypoint     // current waypoint     ctx.beginpath();     ctx.moveto(points[t-1].x,points[t-1].y);     ctx.lineto(points[t].x,points[t].y);     ctx.stroke();     // increment "t" next waypoint     t++; }

Comments

Post a Comment

Popular posts from this blog

c++ - OpenCV Error: Assertion failed <scn == 3 ::scn == 4> in unknown function, -

-
i read alot other solution still confused should mine... #include <opencv2/objdetect/objdetect.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <stdio.h> using namespace std; using namespace cv; int main(int argc, const char** argv) { //create cascade classifier object used face detection cascadeclassifier face_cascade; //use haarcascade_frontalface_alt.xml library face_cascade.load("haarcascade_frontalface_alt.xml"); //setup video capture device , link first capture device videocapture capturedevice; capturedevice.open(0); //setup image files used in capture process mat captureframe; mat grayscaleframe; //create window present results namedwindow("outputcapture", 1); //create loop capture , find faces while (true) { //capture new image frame capturedevice >> captureframe; ...
Read more

php - render data via PDO::FETCH_FUNC vs loop -

-
i've been using 2 methods render data. the first one: function name($id,$name){ return '<div id="'.$id.'">'.$name.'</div>'; } echo implode($pdo->query("select id,name user")->fetchall(pdo::fetch_func,'name')); the second one: $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); foreach($users $user){ echo name($user->id,$user->name); } i don't understand how pdo::fetch_func works. tried figure out. however, not well-documented. could please explain fetch mode? , also, 1 performs better? thank you. both methods wrong , have learn how use templates , how separate business logic presentation logic. $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); tpl::assign('users', $users); is code business logic part. then in template <?php foreach $users $row): ?> <div id="<?=$...
Read more

The canvas has been tainted by cross-origin data in chrome only -

-
uncaught securityerror: failed execute 'getimagedata' on 'canvasrenderingcontext2d': canvas has been tainted cross-origin data i getting above error in chrome. code(following) works fine in mozilla. have not corss domain issue. why above error in chrome? var wheel_canvas, wheel_context, can_w, can_h, wheel_grd; var large_radius = 160; var small_radius = 120; var wheel_canvas = document.getelementbyid('wheel_canvas'); var wheel_context = wheel_canvas.getcontext('2d'); var can_w = $(wheel_canvas).width(); var can_h = $(wheel_canvas).height(); var centerx = can_w / 2, centery = can_h / 2; var wheel_grd = null; test('#ff0000'); function test(hex) { $('#clrpicker').css({'left': 210, 'top': 210 }); inverted = hexbw(hex); $('#color_val_show').val(hex); current_color_hex_val_selected = hex; $('#color_val_show').css({'color':inverted,'background':hex}); fillgradient...
Read more