document.title = '全画面キラキラカードホログラム';

var style = document.createElement('style');
style.innerText = 'html,body{overflow:hidden;cursor:none;user-select:none;}';
document.getElementsByTagName('head').item(0).appendChild(style);

var canvas = document.createElement('canvas');
var w = document.body.clientWidth;
var h = document.body.clientHeight;
var min = Math.min(w,h);

var hue = 90;
canvas.setAttribute('width',w);
canvas.setAttribute('height',h);
let demo = document.getElementById('demo');
demo.appendChild(canvas);


let styleImg = document.createElement('style');
styleImg.innerText = '#demo img{position:absolute;top:50%;left:50%;transform:translate(-50%, -50%);height:100vh;opacity:1;cursor:none;}';
document.getElementsByTagName('head').item(0).appendChild(styleImg);
let img = document.createElement('img');
demo.appendChild(img);
img.src = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw%3D%3D';

let search = location.search.slice(1);
let params = new URLSearchParams(search);
let q = params.get('q');
if(q){
  img.src = q;
}

var ctx = canvas.getContext('2d');
var cx = w/2;
var cy = h/2;
var t = 0;
var y=0;
var iw = min/20;

var i1 = 0;


var canvas2 = document.createElement('canvas');
canvas2.setAttribute('width',w);
canvas2.setAttribute('height',h);
var ctx2 = canvas2.getContext('2d');
demo.appendChild(canvas2);

var w = min;
var h = min;
var w2 = min / 2;
var h2 = min / 2;
var r = Math.sqrt(w2 * w2 + h2 * h2);
var lut = [];
var pos = 0;

function toPolar(){

  for (var y = 0; y < h; y++){
    for (var x = 0; x < w; x++){
      var sx = Math.atan2(y - h2, x - w2) * w2 / Math.PI + w2;
      var sy = Math.sqrt((x - h2) * (x - w2) + (y - h2) * (y - h2));
      sy = (r - sy) / r;
      sy = h - sy * sy * h - 1;

      if (sx < 0) sx = 0;
      if (w - 1 < sx) sx = w - 1;
      if (sy < 0) sy = 0;
      if (h - 1 < sy) sy = h - 1;

      sx = Math.round(sx);
      sy = Math.round(sy);

      lut[pos++] = (sy * w + sx) * 4 + 0;
      lut[pos++] = (sy * w + sx) * 4 + 1;
      lut[pos++] = (sy * w + sx) * 4 + 2;
      lut[pos++] = (sy * w + sx) * 4 + 3;
    }
  }
}

function iToRGB(i) {
  return 'rgb('+ rgbAry[i].join(',') +')';
}

//h:0-180
function iToHSL(h,s,l) {
  return 'hsl(' + h + ', '+s+'%, '+l+'%)';
}
function iToC(i) {
  var c;
  if(i === 0){
    c = iToHSL(hue,100,30);
  } else if(i===1){
    c = iToHSL(hue,100,90);
  } else if(i===3){
    c = iToHSL(hue,100,80);
  } else if(i===4){
    c = iToHSL(hue,100,40);
  } else {
    c = iToHSL(hue,100,50);
  }
  return c;
}



function draw() {

  var grad = ctx2.createLinearGradient(0, 0, w, 0);
  grad.addColorStop(1/16, iToC(4));
  grad.addColorStop(1/8, iToC(0));
  grad.addColorStop(3/16, iToC(4));
  grad.addColorStop(5/16, iToC(3));
  grad.addColorStop(3/8, iToC(1));
  grad.addColorStop(7/16, iToC(3));
  grad.addColorStop(9/16, iToC(4));
  grad.addColorStop(5/8, iToC(0));
  grad.addColorStop(11/16, iToC(4));
  grad.addColorStop(13/16, iToC(3));
  grad.addColorStop(7/8, iToC(1));
  grad.addColorStop(15/16, iToC(3));
  ctx2.fillStyle = grad;
  ctx2.fillRect(0,0,min,min);

  var output = ctx2.getImageData(0,0,w,h);
  var imageData = ctx2.getImageData(0,0,w,h);
  var src = imageData.data;
  var dst = output.data;
  for (var n = 0; n < h * w * 4; n++){
      dst[n] = src[lut[n]];
  }

  ctx2.putImageData(output, 0, 0);
  var img = new Image();
  img.src = canvas2.toDataURL();
  img.onload = function () {
    //ctx.clearRect(0, 0, min, min)
    rot = 45 * Math.PI / 180;
    drawPanel(img);
  }
}

function drawPanel(img){
  var w = document.body.clientWidth;
  var h = document.body.clientHeight;
  for(i=0;i*iw<w;i++){
    for(j=0;j*iw<h;j++){
      ctx.drawImage(img, 0, 0, min, min, i*iw, j*iw, iw,iw);
    }
  }
}

toPolar();
draw();

setInterval(function(){
  hue = Math.random()*360;
  draw();
}, 9999);






// ファイルアップロード
var dragArea = document.getElementById('demo');
dragArea.classList.add('ready');
dragArea.addEventListener('dragstart', function(event){
  event.dataTranfer.addElement(container);
});
dragArea.addEventListener('dragover', function(event){
  event.preventDefault();
  this.classList.add('drag');
});
dragArea.addEventListener('dragleave', function(event){
  event.preventDefault();
  this.classList.remove('drag');
});
dragArea.addEventListener('drop', function(event){
  event.preventDefault();
  this.classList.remove('drag');
  console.log(event.dataTransfer.files);
  if(!event.dataTransfer.files.length){
    return;
  }
  var file = event.dataTransfer.files[0];
  fileName = file.name.substring(0,12).split('.')[0] || 'name';
  console.log(file);

  var reader = new FileReader();
  reader.readAsDataURL(file)

  reader.addEventListener('load', function(){
    var dataURL = reader.result;
    console.log(dataURL);

    var newImage = new Image();
    img.src = dataURL;
    newImage.src = dataURL;
    newImage.onload = function(){
    }
  });
});


let opacity = 1;
img.addEventListener('click', function(ev) {
  opacity -= 0.2;
  if(opacity < 0.4){
    opacity = 1;
  }
  img.style.opacity = opacity;
}, false );


document.oncontextmenu = function () {return false;}
function resize() {
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;
  console.table({w:canvas.width, h:canvas.height});
  w = document.body.clientWidth;
  h = document.body.clientHeight;
  cx = w/2;
  cy = h/2;

  w2 = w/2;
  h2 = h/2;
}

window.onresize = resize;
window.addEventListener('click', function(ev) {
  hue = Math.random()*360;
  //resize();
  //document.body.requestFullscreen();
  draw();
}, false );

window.addEventListener('dblclick', function(ev) {
  //draw();
}, false );

document.addEventListener('fullscreenchange',function(e){
  resize();
});

ページのソースを表示 : Ctrl+U , DevTools : F12

view-source:https://hi0a.com/demo/-js/js-canvas-kirakira/