editCanvas.js

var editCanvas = document.querySelector("#edit-canvas")
editCanvas.height = 400
editCanvas.width = 600

var ctx = editCanvas.getContext('2d')

// Title and Title Background
var titleComponent = {
  properties: {
    text: function () {
      return document.querySelector("#title").value
    },
    bgColor: function () {
      return $("#title-color").colorpicker('getValue')
    }
  },
  draw: function () {
    this._bg()
    this._text()
  },
  _bg: function () {
    ctx.fillStyle = this.properties.bgColor()
    ctx.fillRect(0, 300, 500, 120)
  },
  _text: function () {
    editCanvas.letterSpacing = 2
    ctx.fillStyle = 'rgba(255, 255, 255, 1)'
    ctx.font = '30px sans-serif'
    ctx.textAlign = 'center'
    ctx.textBaseline = 'top'

    function wrapText(context, text, x, y, maxWidth, lineHeight) {
      var words = text.split(' ')
      var line = ''

      for (var n = 0; n < words.length; n++) {
        var testLine = line + words[n] + ' '
        var metrics = context.measureText(testLine)
        var testWidth = metrics.width
        if (testWidth > maxWidth && n > 0) {
          context.fillText(line, x, y)
          line = words[n] + ' '
          y += lineHeight
        } else {
          line = testLine
        }
      }
      context.fillText(line, x, y)
    }
    wrapText(ctx, this.properties.text(), 255, 326, 450, 35)
  }
}

// Category and Category Background
var categoryComponent = {
  properties: {
    text: function () {
      return document.querySelector('#category').value
    },
    bgColor: function () {
      return $("#category-color").colorpicker('getValue')
    }
  },
  draw: function () {
    this._bg()
    this._text()
  },
  _bg: function () {
    ctx.fillStyle = this.properties.bgColor()
    ctx.fillRect(500, 0, 150, 400)
  },
  _text: function () {
    ctx.save()
    ctx.translate(524, 200)
    ctx.rotate(-0.5 * Math.PI)
    editCanvas.style.letterSpacing = 4
    ctx.fillStyle = 'rgba(255, 255, 255, 0.8)'
    ctx.font = (this.properties.text().length > 18) ? '37px sans-serif' : '48px sans-serif'
    ctx.textAlign = "center"
    ctx.fillText(this.properties.text(), 0, 0)
    ctx.restore()
  }
}

// Background Image
var backgroundComponent = {
  properties: {
    domId: "#background"
  },
  draw: function () {
    this._addImage()
  },
  _addImage: function () {
    var file = document.querySelector(this.properties.domId).files[0]

    var background = new Image()
    background.crossOrigin = "Anonymous"
    var reader = new FileReader()

    background.onload = function () {
      sourceHeight = background.height
      sourceWidth = background.width
      ctx.globalCompositeOperation = 'destination-over'
      ctx.drawImage(background, 0, 0, sourceWidth, sourceHeight,
        0, 0, 600, 400)
      ctx.globalCompositeOperation = 'source-over'
    }

    if (file) {
      reader.addEventListener("load", function () {
        background.src = reader.result
      }, false)

      reader.readAsDataURL(file)
    }

    if (!file && document.querySelector('#background-url').value !== '') {
      background.src = document.querySelector('#background-url').value
    }
  }
}

// Logo

var logoComponent = {
  properties: {
    domId: "#logo",
  },
  draw: function () {
    this._addImage()
  },
  _addImage: function () {

    var file = document.querySelector(this.properties.domId).files[0]
    var background = new Image()
    background.crossOrigin = "Anonymous"
    var reader = new FileReader()

    background.onload = function () {
      sourceHeight = background.height
      sourceWidth = background.width
      ctx.drawImage(background, 0, 0, sourceWidth, sourceHeight,
        5, 5, 145, 145)
    }

    if (file) {
      reader.addEventListener("load", function () {
        background.src = reader.result
      }, false)

      reader.readAsDataURL(file)
    }

    if (!file && document.querySelector('#logo-url').value !== '') {
      background.src = document.querySelector('#logo-url').value
    }
  }
}

// main function to draw / redraw canvas
function draw() {
  //Draw Title Component
  ctx.clearRect(0, 0, editCanvas.width, editCanvas.height)
  titleComponent.draw()
  categoryComponent.draw()
  backgroundComponent.draw()
  logoComponent.draw()

  //Store to local storage.. next
}

document.addEventListener('DOMContentLoaded', function () {
  // Color Picker
  $('#title-color').colorpicker({
    component: '.btn'
  }).on('changeColor', draw)

  $('#category-color').colorpicker({
    component: '.btn'
  }).on('changeColor', draw)

  // Update Events
  document.querySelector('#title').addEventListener('keyup', draw)
  document.querySelector('#category').addEventListener('change', draw)
  document.querySelector('#background')
    .addEventListener('change', draw)
  document.querySelector('#logo')
    .addEventListener('change', draw)

  // Any Query Params?
  if (getUrlParameter('titleColor')) {
    $("#title-color")
      .colorpicker('setValue', 'rgba(' + getUrlParameter('titleColor') + ')')
  }
  if (getUrlParameter('sidebarColor')) {
    $("#category-color")
      .colorpicker('setValue', 'rgba(' + getUrlParameter('sidebarColor') + ')')
  }
  if (getUrlParameter('title')) {
    $("#title").val(getUrlParameter('title'))
  }
  if (getUrlParameter('category')) {
    $("#category option").each(function (i, opt) {
      if ($(opt).val().toLowerCase() == getUrlParameter('category').toLowerCase()) {
        $(opt).attr('selected', true)
      }
    })
  }
  if (getUrlParameter('background')) {
    $("#background-url").val(getUrlParameter('background'))
  }
  if (getUrlParameter('logo')) {
    $("#logo-url").val(getUrlParameter('logo'))
  }

  // Select Dropdowns to Material Styles
  var elems = document.querySelectorAll('select')
  instances = M.FormSelect.init(elems)

  draw()

  document.querySelector('#download-image').addEventListener('click', function () {
    //to png
    var img = document.createElement('img')
    img.src = editCanvas.toDataURL()
    var a = document.createElement('a')
    a.href = img.src
    a.download = 'thumbnail.png'
    document.body.appendChild(a)
    a.click()
    document.body.removeChild(a)
  })
})

// Helper function to get URL Query Params
function getUrlParameter(name) {
  name = name.replace(/[\[]/, '\\[').replace(/[\]]/, '\\]')
  var regex = new RegExp('[\\?&]' + name + '=([^&#]*)')
  var results = regex.exec(location.search)
  return results === null ? false : decodeURIComponent(results[1].replace(/\+/g, ' '))
}

// Hidden function for users to generate a shareable URL
var developer = {}
developer.getShareUrl = function () {
  var params = {}
  params.title = titleComponent.properties.text()
  params.titleColor = titleComponent.properties.bgColor().replace(/(rgba|\(|\))/g, '')
  params.sidebarColor = categoryComponent.properties.bgColor().replace(/(rgba|\(|\))/g, '')
  params.category = categoryComponent.properties.text()
  // background and logo will need base64

  return window.location.origin + window.location.pathname + '?' + generateQueryParams(params)

  function generateQueryParams(obj) {
    var str = ""
    for (var key in obj) {
        if (str != "") {
            str += "&"
        }
        str += key + "=" + encodeURIComponent(obj[key])
    }
    return str
  }
}