Created
February 25, 2018 11:01
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Core HTML Canvas Samples Codes with ES6
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| const canvas = document.getElementById('canvas'), | |
| context = canvas.getContext('2d'), | |
| slidesSelect = document.getElementById('sideSelect'), | |
| startAngleSelect = document.getElementById('startAngleSelect'), | |
| fillCheckbox = document.getElementById('fillCheckbox'), | |
| mosuseDown = {x:0, y: 0}, | |
| rubberBandRect = {} | |
| class Point { | |
| constructor(x,y) { | |
| this.x = x | |
| this.y = y | |
| } | |
| } | |
| function getPolygonPoints(centerX, centerY, radius, sides, startAngle) { | |
| let points = [], | |
| angle = startAngle | |
| for(let i = 0; i < sides; i++) { | |
| points.push(new Point(centerX + radius * Math.sin(angle), | |
| centerY - radius * Math.cos(angle))) | |
| angle += 2*Math.PI/sides | |
| } | |
| return points | |
| } | |
| function createPolygonPath(startX, centerY, radius, sides, startAngle) { | |
| const points = getPolygonPoints(startX, centerY, radius, sides, startAngle) | |
| context.beginPath() | |
| context.moveTo(points[0].x, points[0].y) | |
| for (let i = 1; i < sides; ++i) { | |
| context.lineTo(points[i].x, points[i].y) | |
| } | |
| context.closePath() | |
| } | |
| function drawRubberbandShape(loc, sides, startAngle) { | |
| createPolygonPath(mosuseDown.x, | |
| mosuseDown.y, | |
| rubberBandRect.width, | |
| parseInt(slidesSelect.value), | |
| (Math.PI/180)*parseInt(startAngleSelect.value)) | |
| context.stroke() | |
| if (fillCheckbox.checked) | |
| context.fill() | |
| } |
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <title>Sprite Sheets</title> | |
| <style type="text/css"> | |
| body { | |
| background: #dddddd; | |
| } | |
| #canvas { | |
| position: absolute; | |
| left: 0px; | |
| top: 20px; | |
| margin: 20px; | |
| background: #ffffff; | |
| border: thin inset rgba(100,150,230, 0.5); | |
| cursor: pointer; | |
| } | |
| #readout { | |
| margin-top: 10px; | |
| margin-left: 15px; | |
| color: blue; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div id="readout"></div> | |
| <canvas id="canvas" width="500" height="250"> | |
| Canvas not supported | |
| </canvas> | |
| <script type="text/javascript"> | |
| const canvas = document.getElementById('canvas'), | |
| readout = document.getElementById('readout'), | |
| context = canvas.getContext('2d'), | |
| spriteSheet = new Image(); | |
| const windowToCanvas = (c, x ,y) => { | |
| const bbox = c.getBoundingClientRect(); | |
| return { | |
| x: x-bbox.left*(c.width/bbox.width), | |
| y: y-bbox.top*(c.height/bbox.height) | |
| } | |
| }; | |
| const drawBackground = () => { | |
| const VERTICAL_LINE_SPACING = 12; | |
| for(let i = context.canvas.height; | |
| i > VERTICAL_LINE_SPACING*4; | |
| i-=VERTICAL_LINE_SPACING) { | |
| context.beginPath(); | |
| context.moveTo(0, i); | |
| context.lineTo(context.canvas.width, i); | |
| context.stroke(); | |
| } | |
| }; | |
| const drawSpriteSheet = () => context.drawImage(spriteSheet, 0 ,0); | |
| const drawGuidelines = (x,y) => { | |
| context.strokeStyle = 'rgba(0,0,230,0.8)'; | |
| context.lineWidth = 0.5; | |
| drawVerticalLine(x); | |
| drawHorizontalLine(y); | |
| }; | |
| const drawHorizontalLine = (y) => { | |
| context.beginPath(); | |
| context.moveTo(0,y+0.5); | |
| context.lineTo(context.canvas.width, y+0.5); | |
| context.stroke(); | |
| }; | |
| const updateReadout = (x, y) => readout.innerText = ` | |
| (${x.toFixed(0)}, ${y.toFixed(0)}) | |
| `; | |
| const drawVerticalLine = (x) => { | |
| context.beginPath(); | |
| context.moveTo(x+0.5, 0); | |
| context.lineTo(x+0.5, context.canvas.height); | |
| context.stroke(); | |
| }; | |
| canvas.onmousemove = (e) => { | |
| const loc = windowToCanvas(canvas, e.clientX, e.clientY); | |
| drawBackground(); | |
| drawSpriteSheet(); | |
| drawGuidelines(loc.x, loc.y); | |
| updateReadout(loc.x, loc.y); | |
| }; | |
| spriteSheet.src = './running-sprite-sheet.png'; | |
| spriteSheet.onload = () => drawSpriteSheet(); | |
| drawBackground(); | |
| </script> | |
| </body> | |
| </html> |
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