A way to "toggle" image in canvas as if it was gif

Question

I am looking for an easy way, if there is one, in animating (toggling, swipping, like a gif) images on canvas (hmtl5/js), I am crating a game for collage and I'd like the images to look as animated (fake a sprite), since JavaScript doesn't support gifs.

My images are inserted like this:

var playerReady = false;
var playerImage = new Image();
playerImage.onload = function () {
    playerReady = true;
};
playerImage.src = "images/ship.png";

Answer 1

The idea is to fetch a series of images (maybe all at once on a spritesheet) and then use a timed animation loop to sequentially display each image in the series on the canvas. Display == 1. Clear the canvas, 2. Draw the next sprite.

Here's annotated example code and a Demo:

// canvas related variables
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");

// animation related variables
var lastFlap,lastMove;

// define a bird object
// x,y are the position of the bird on the canvas
// spriteX,spriteY is the position of the first desired
//      sprite image on the spritesheet
// width,height is the size of 1 sprite image
// currentFrame is the index of which of the sprite images to display
// currentDirection.  The sprite plays forward and then backward to
//      accomplish 1 flap.  This determines if the next frame index will
//      be increased (play forward) or decreased (play backward)

var bird={
  x:30,
  y:30,
  spriteX:0,
  spriteY:52,
  width:51,
  height:51,
  frames:4,
  currentFrame:0,
  currentDirection:1
}

// load the spritesheet and start the animation
var spritesheet=new Image();
spritesheet.onload=start;
spritesheet.src="https://dl.dropboxusercontent.com/u/139992952/multple/birdSpritesheet.png";
function start(){
  requestAnimationFrame(animate);
}


function animate(time){

  // request another animation frame           
  if(bird.x<canvas.width){
    requestAnimationFrame(animate);
  }

  // if the lastFlap or lastMove times don't aren't set, then set them
  if(!lastFlap){lastFlap=time;}
  if(!lastMove){lastMove=time;}

  // calculate the elapsed times since the last flap and the last move            
  var elapsedFlap=time-lastFlap;
  var elapsedMove=time-lastMove;

  // if 50ms have elapsed, advance to the next image in this sprite
  if(elapsedFlap>50){

    // advance to next sprite on the spritesheet (flap)
    bird.currentFrame+=bird.currentDirection;

    // clamp bird.currentFrame between 0-3  (0,1,2,3)
    // (because there are 4 images that make up the whole bird sprite)
    if(bird.currentFrame<0 || bird.currentFrame>bird.frames-1){
      bird.currentDirection*=-1;
      bird.currentFrame+=bird.currentDirection;
    }

    // reset the flap timer
    lastFlap=time;
  }

  // locate the current sprite from the spritesheet
  var sx=bird.spriteX+bird.currentFrame*bird.width;
  var sy=bird.spriteY;

  // if 100ms have elapsed, move the bird across the canvas
  if(elapsedMove>100){
    bird.x+=3;
    lastMove=time;
  }

  // clear the whole canvas            
  ctx.clearRect(0,0,canvas.width,canvas.height);

  // draw the current part of the bird sprite at the current bird.x            
  ctx.drawImage(spritesheet,
                sx,sy,bird.width,bird.height,
                bird.x,bird.y,bird.width,bird.height
               );

}

body{ background-color: white; }
canvas{border:1px solid red;}

<h4>"Playing" a series of sprites.</h4>
<canvas id="canvas" width=300 height=300></canvas>