spee.ch/public/assets/js/memeDraw.js

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var canvas = document.getElementById('meme-canvas');
var img = document.getElementById('start-image');
var canvasWidth;
var canvasHeight;
var fontSize = 28;
var topText = document.getElementById('top-text');
var bottomText = document.getElementById('bottom-text');
var ctx = canvas.getContext('2d');
// create the canvas
img.onload = function() {
// get dimensions of the start img
canvasWidth = img.width;
canvasHeight = img.height;
// hide start image
img.hidden = true;
// size the canvas
canvas.width = canvasWidth;
canvas.height = canvasHeight;
// draw the starting meme
drawMeme()
}
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function newCanvas(image){
// hide start image
img = image;
// get dimensions of the start img
canvasHeight = canvasWidth * (img.height / img.width);
// size the canvas
canvas.width = canvasWidth;
canvas.height = canvasHeight;
// draw the meme
drawMeme()
}
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// if the text changes, re-draw the meme
topText.addEventListener('keyup', drawMeme);
bottomText.addEventListener('keyup', drawMeme);
// draw the image and draw the text over it
function drawMeme() {
ctx.clearRect(0, 0, canvasWidth, canvasHeight);
ctx.drawImage(img, 0, 0, canvasWidth, canvasHeight);
ctx.lineWidth = 4;
ctx.font = fontSize + 'px sans-serif';
ctx.strokeStyle = 'black';
ctx.fillStyle = 'white';
ctx.textAlign = 'center';
ctx.textBaseline = 'top';
var text1 = topText.value;
text1 = text1.toUpperCase();
x = canvasWidth / 2;
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y = 5;
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wrapText(ctx, text1, x, y, canvasWidth, fontSize, false);
ctx.textBaseline = 'bottom';
var text2 = bottomText.value;
text2 = text2.toUpperCase();
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y = canvasHeight - 5;
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wrapText(ctx, text2, x, y, canvasHeight, fontSize, true);
}
function wrapText(context, text, x, y, maxWidth, lineHeight, fromBottom) {
var pushMethod = (fromBottom)?'unshift':'push';
lineHeight = (fromBottom)?-lineHeight:lineHeight;
var lines = [];
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var y = y;
var line ='';
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var words = text.split(' ');
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for (var i = 0; i < words.length; i++) {
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var testLine = line + ' ' + words[i];
var metrics = context.measureText(testLine);
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var testWidth = metrics.width;
if (testWidth > maxWidth) {
lines[pushMethod](line);
line = words[i] + ' ';
} else {
line = testLine;
}
}
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lines[pushMethod](line);
for (var k in lines ) {
context.strokeText(lines[k], x, y + lineHeight * k);
context.fillText(lines[k], x, y + lineHeight * k);
}
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}