87 lines
2.2 KiB
Plaintext
87 lines
2.2 KiB
Plaintext
'use strict';
|
|
|
|
/* eslint-disable consistent-return */
|
|
|
|
var str2arr = require('../common').str2arr;
|
|
var sliceEq = require('../common').sliceEq;
|
|
var readUInt16LE = require('../common').readUInt16LE;
|
|
var readUInt16BE = require('../common').readUInt16BE;
|
|
var readUInt32LE = require('../common').readUInt32LE;
|
|
var readUInt32BE = require('../common').readUInt32BE;
|
|
|
|
|
|
var SIG_1 = str2arr('II\x2A\0');
|
|
var SIG_2 = str2arr('MM\0\x2A');
|
|
|
|
|
|
function readUInt16(buffer, offset, is_big_endian) {
|
|
return is_big_endian ? readUInt16BE(buffer, offset) : readUInt16LE(buffer, offset);
|
|
}
|
|
|
|
function readUInt32(buffer, offset, is_big_endian) {
|
|
return is_big_endian ? readUInt32BE(buffer, offset) : readUInt32LE(buffer, offset);
|
|
}
|
|
|
|
function readIFDValue(data, data_offset, is_big_endian) {
|
|
var type = readUInt16(data, data_offset + 2, is_big_endian);
|
|
var values = readUInt32(data, data_offset + 4, is_big_endian);
|
|
|
|
if (values !== 1 || (type !== 3 && type !== 4)) return null;
|
|
|
|
if (type === 3) {
|
|
return readUInt16(data, data_offset + 8, is_big_endian);
|
|
}
|
|
|
|
return readUInt32(data, data_offset + 8, is_big_endian);
|
|
}
|
|
|
|
module.exports = function (data) {
|
|
if (data.length < 8) return;
|
|
|
|
// check TIFF signature
|
|
if (!sliceEq(data, 0, SIG_1) && !sliceEq(data, 0, SIG_2)) return;
|
|
|
|
var is_big_endian = (data[0] === 77 /* 'MM' */);
|
|
var count = readUInt32(data, 4, is_big_endian) - 8;
|
|
|
|
if (count < 0) return;
|
|
|
|
// skip until IFD
|
|
var offset = count + 8;
|
|
|
|
if (data.length - offset < 2) return;
|
|
|
|
// read number of IFD entries
|
|
var ifd_size = readUInt16(data, offset + 0, is_big_endian) * 12;
|
|
|
|
if (ifd_size <= 0) return;
|
|
|
|
offset += 2;
|
|
|
|
// read all IFD entries
|
|
if (data.length - offset < ifd_size) return;
|
|
|
|
var i, width, height, tag;
|
|
|
|
for (i = 0; i < ifd_size; i += 12) {
|
|
tag = readUInt16(data, offset + i, is_big_endian);
|
|
|
|
if (tag === 256) {
|
|
width = readIFDValue(data, offset + i, is_big_endian);
|
|
} else if (tag === 257) {
|
|
height = readIFDValue(data, offset + i, is_big_endian);
|
|
}
|
|
}
|
|
|
|
if (width && height) {
|
|
return {
|
|
width: width,
|
|
height: height,
|
|
type: 'tiff',
|
|
mime: 'image/tiff',
|
|
wUnits: 'px',
|
|
hUnits: 'px'
|
|
};
|
|
}
|
|
};
|