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/* Cut down version of https://github.com/exif-js/exif-js
* only looking for orientation EXIF data. MIT. */
(function() {
var EXIF = {};
window.EXIF = EXIF;
function readEXIFData(file, start) {
var str = "";
for (var n = start; n < start+4; n++) {
str += String.fromCharCode(file.getUint8(n));
}
if (str != "Exif") {
return false;
}
var bigEnd,
tiffOffset = start + 6;
// test for TIFF validity and endianness
if (file.getUint16(tiffOffset) == 0x4949) {
bigEnd = false;
} else if (file.getUint16(tiffOffset) == 0x4D4D) {
bigEnd = true;
} else {
return false;
}
if (file.getUint16(tiffOffset+2, !bigEnd) != 0x002A) {
return false;
}
var firstIFDOffset = file.getUint32(tiffOffset+4, !bigEnd);
if (firstIFDOffset < 0x00000008) {
return false;
}
var dirStart = tiffOffset + firstIFDOffset,
entries = file.getUint16(dirStart, !bigEnd),
tags = {},
entryOffset,
i;
for (i=0;i<entries;i++) {
entryOffset = dirStart + i*12 + 2;
if (file.getUint16(entryOffset, !bigEnd) == 0x0112) {
return parseInt(file.getUint16(entryOffset + 8, !bigEnd), 10);
}
}
return false;
}
EXIF.getData = function(img) {
if ((img instanceof Image || img instanceof HTMLImageElement) && !img.complete) {
return false;
}
var data = img.src;
if (data.match(/^http/)) {
// We're loading this image from the server, presumably after a
// submission, so we have its URL, not yet its data.
var canvas = document.createElement("canvas"),
ctx = canvas.getContext("2d");
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
data = canvas.toDataURL("image/jpeg");
}
var base64 = data.replace(/^data\:([^\;]+)\;base64,/gmi, '');
var binary = atob(base64);
var len = binary.length;
var file = new ArrayBuffer(len);
var view = new Uint8Array(file);
for (var i = 0; i < len; i++) {
view[i] = binary.charCodeAt(i);
}
var dataView = new DataView(file);
if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
return false; // not a valid jpeg
}
var offset = 2,
length = file.byteLength,
marker;
while (offset < length) {
if (dataView.getUint8(offset) != 0xFF) {
return false; // not a valid marker, something is wrong
}
marker = dataView.getUint8(offset + 1);
// we could implement handling for other markers here,
// but we're only looking for 0xFFE1 for EXIF data
if (marker == 225) {
return readEXIFData(dataView, offset + 4);
// offset += 2 + file.getShortAt(offset+2, true);
} else {
offset += 2 + dataView.getUint16(offset+2);
}
}
};
})();
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