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function renderToCanvas(img, options) {
if (!img) return
options = options || {}
// Canvas max size for any side
var maxSize = 2000
var canvas = document.createElement('canvas')
var ctx = canvas.getContext('2d')
var initialScale = options.scale || 1
// Scale to needed to constrain canvas to max size
// var scale = getScale(img.width * initialScale,
// img.height * initialScale, maxSize, maxSize)
var scale = 1
// Still need to apply the user defined scale
scale *= initialScale
var width = canvas.width = Math.round(img.width * scale)
var height = canvas.height = Math.round(img.height * scale)
var correctOrientation = options.correctOrientation
var jpeg = !!img.src.match(/data:image\/jpeg|\.jpeg$|\.jpg$/i)
var dataURI = !!img.src.match(/^data:/)
ctx.save()
// Can only correct orientation on JPEGs represented as dataURIs
// for the time being
if (correctOrientation && jpeg && dataURI) {
applyOrientationCorrection()
}
// Resize image if too large
if (scale !== 1) {
ctx.scale(scale, scale)
}
ctx.drawImage(img, 0, 0)
ctx.restore()
return canvas
function applyOrientationCorrection() {
var orientation = getOrientation(img.src)
// Only apply transform if there is some non-normal orientation
if (orientation && orientation !== 1) {
var transform = orientationToTransform[orientation]
var rotation = transform.rotation
var mirror = transform.mirror
var flipAspect = rotation === 90 || rotation === 270
if (flipAspect) {
// Fancy schmancy swap algo
canvas.width = canvas.height + canvas.width
canvas.height = canvas.width - canvas.height
canvas.width -= canvas.height
}
if (rotation > 0) {
applyRotation(rotation)
}
if (mirror) {
// TODO This is broken. Not sure how to apply this transform
// No biggie, we don't run into this case ATM
// applyMirror()
}
}
}
/**
* Some images are friggin rotated n shit! (iOS)
* wut the heck
* dang it
* man
* read the EXIF data
* return EXIF orientation value
*/
function getOrientation(uri) {
var exif = new ExifReader
// Split off the base64 data
var base64String = uri.split(',')[1]
// Read off first 128KB, which is all we need to
// get the EXIF data
var arr = base64ToUint8Array(base64String, 0, Math.pow(2, 17))
try {
exif.load(arr.buffer)
return exif.getTagValue('Orientation')
} catch (err) {
return 1
}
}
/**
* Apply rotation such that rotated image will be
* centered in canvas
*/
function applyRotation(deg) {
var radians = deg * (Math.PI / 180)
if (deg === 90) {
ctx.translate(canvas.width, 0)
} else if (deg === 180) {
ctx.translate(canvas.width, canvas.height)
} else if (deg == 270) {
ctx.translate(0, canvas.height)
}
ctx.rotate(radians)
}
function applyMirror() {
ctx.scale(-1, 1)
}
}
var orientationToTransform = {
1: { rotation: 0, mirror: false },
2: { rotation: 0, mirror: true },
3: { rotation: 180, mirror: false },
4: { rotation: 180, mirror: true },
5: { rotation: 90, mirror: true },
6: { rotation: 90, mirror: false },
7: { rotation: 270, mirror: true },
8: { rotation: 270, mirror: false }
}
function base64ToUint8Array(string, start, finish) {
var start = start || 0
var finish = finish || string.length
// atob that shit
var binary = atob(string)
var buffer = new Uint8Array(binary.length)
for (var i = start; i < finish; i++) {
buffer[i] = binary.charCodeAt(i)
}
return buffer
}
var dataUriToUint8Array = function(uri){
var data = uri.split(',')[1];
var bytes = atob(data);
var buf = new ArrayBuffer(bytes.length);
var u8 = new Uint8Array(buf);
for (var i = 0; i < bytes.length; i++) {
u8[i] = bytes.charCodeAt(i);
}
return u8
}
window.dataUriToBlob = (function(){
/**
* Blob constructor.
*/
var Blob = window.Blob;
/**
* ArrayBufferView support.
*/
var hasArrayBufferView = new Blob([new Uint8Array(100)]).size == 100;
/**
* Return a `Blob` for the given data `uri`.
*
* @param {String} uri
* @return {Blob}
* @api public
*/
var dataUriToBlob = function(uri){
var data = uri.split(',')[1];
var bytes = atob(data);
var buf = new ArrayBuffer(bytes.length);
var arr = new Uint8Array(buf);
for (var i = 0; i < bytes.length; i++) {
arr[i] = bytes.charCodeAt(i);
}
if (!hasArrayBufferView) arr = buf;
var blob = new Blob([arr], { type: mime(uri) });
blob.slice = blob.slice || blob.webkitSlice;
return blob;
};
/**
* Return data uri mime type.
*/
function mime(uri) {
return uri.split(';')[0].slice(5);
}
return dataUriToBlob;
})()
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