jeotiff
Version:
GeoTIFF image decoding in JavaScript
262 lines (234 loc) • 8.67 kB
JavaScript
"use strict";
var globals = require("./globals.js");
var GeoTIFFImage = require("./geotiffimage.js");
var DataView64 = require("./dataview64.js");
var fieldTypes = globals.fieldTypes,
fieldTagNames = globals.fieldTagNames,
arrayFields = globals.arrayFields,
geoKeyNames = globals.geoKeyNames;
/**
* The abstraction for a whole GeoTIFF file.
* @constructor
* @param {ArrayBuffer} rawData the raw data stream of the file as an ArrayBuffer.
* @param {Object} [options] further options.
* @param {Boolean} [options.cache=false] whether or not decoded tiles shall be cached.
*/
function GeoTIFF(rawData, options) {
this.dataView = new DataView64(rawData);
options = options || {};
this.cache = options.cache || false;
var BOM = this.dataView.getUint16(0, 0);
if (BOM === 0x4949) {
this.littleEndian = true;
}
else if (BOM === 0x4D4D) {
this.littleEndian = false;
}
else {
throw new TypeError("Invalid byte order value.");
}
var magicNumber = this.dataView.getUint16(2, this.littleEndian);
if (this.dataView.getUint16(2, this.littleEndian) === 42) {
this.bigTiff = false;
}
else if (magicNumber === 43) {
this.bigTiff = true;
var offsetBytesize = this.dataView.getUint16(4, this.littleEndian);
if (offsetBytesize !== 8) {
throw new Error("Unsupported offset byte-size.");
}
}
else {
throw new TypeError("Invalid magic number.");
}
this.fileDirectories = this.parseFileDirectories(
this.getOffset((this.bigTiff) ? 8 : 4)
);
}
GeoTIFF.prototype = {
getOffset: function(offset) {
if (this.bigTiff) {
return this.dataView.getUint64(offset, this.littleEndian);
}
return this.dataView.getUint32(offset, this.littleEndian);
},
getFieldTypeLength: function(fieldType) {
switch (fieldType) {
case fieldTypes.BYTE: case fieldTypes.ASCII: case fieldTypes.SBYTE: case fieldTypes.UNDEFINED:
return 1;
case fieldTypes.SHORT: case fieldTypes.SSHORT:
return 2;
case fieldTypes.LONG: case fieldTypes.SLONG: case fieldTypes.FLOAT:
return 4;
case fieldTypes.RATIONAL: case fieldTypes.SRATIONAL: case fieldTypes.DOUBLE:
case fieldTypes.LONG8: case fieldTypes.SLONG8: case fieldTypes.IFD8:
return 8;
default:
throw new RangeError("Invalid field type: " + fieldType);
}
},
getValues: function(fieldType, count, offset) {
var values = null;
var readMethod = null;
var fieldTypeLength = this.getFieldTypeLength(fieldType);
var i;
switch (fieldType) {
case fieldTypes.BYTE: case fieldTypes.ASCII: case fieldTypes.UNDEFINED:
values = new Uint8Array(count); readMethod = this.dataView.getUint8;
break;
case fieldTypes.SBYTE:
values = new Int8Array(count); readMethod = this.dataView.getInt8;
break;
case fieldTypes.SHORT:
values = new Uint16Array(count); readMethod = this.dataView.getUint16;
break;
case fieldTypes.SSHORT:
values = new Int16Array(count); readMethod = this.dataView.getInt16;
break;
case fieldTypes.LONG:
values = new Uint32Array(count); readMethod = this.dataView.getUint32;
break;
case fieldTypes.SLONG:
values = new Int32Array(count); readMethod = this.dataView.getInt32;
break;
case fieldTypes.LONG8: case fieldTypes.IFD8:
values = new Array(count); readMethod = this.dataView.getUint64;
break;
case fieldTypes.SLONG8:
values = new Array(count); readMethod = this.dataView.getInt64;
break;
case fieldTypes.RATIONAL:
values = new Uint32Array(count*2); readMethod = this.dataView.getUint32;
break;
case fieldTypes.SRATIONAL:
values = new Int32Array(count*2); readMethod = this.dataView.getInt32;
break;
case fieldTypes.FLOAT:
values = new Float32Array(count); readMethod = this.dataView.getFloat32;
break;
case fieldTypes.DOUBLE:
values = new Float64Array(count); readMethod = this.dataView.getFloat64;
break;
default:
throw new RangeError("Invalid field type: " + fieldType);
}
// normal fields
if (!(fieldType === fieldTypes.RATIONAL || fieldType === fieldTypes.SRATIONAL)) {
for (i=0; i < count; ++i) {
values[i] = readMethod.call(
this.dataView, offset + (i*fieldTypeLength), this.littleEndian
);
}
}
// RATIONAL or SRATIONAL
else {
for (i=0; i < count; i+=2) {
values[i] = readMethod.call(
this.dataView, offset + (i*fieldTypeLength), this.littleEndian
);
values[i+1] = readMethod.call(
this.dataView, offset + (i*fieldTypeLength + 4), this.littleEndian
);
}
}
if (fieldType === fieldTypes.ASCII) {
return String.fromCharCode.apply(null, values);
}
return values;
},
getFieldValues: function(fieldTag, fieldType, typeCount, valueOffset) {
var fieldValues;
var fieldTypeLength = this.getFieldTypeLength(fieldType);
if (fieldTypeLength * typeCount <= (this.bigTiff ? 8 : 4)) {
fieldValues = this.getValues(fieldType, typeCount, valueOffset);
}
else {
var actualOffset = this.getOffset(valueOffset);
fieldValues = this.getValues(fieldType, typeCount, actualOffset);
}
if (typeCount === 1 && arrayFields.indexOf(fieldTag) === -1 && !(fieldType === fieldTypes.RATIONAL || fieldType === fieldTypes.SRATIONAL)) {
return fieldValues[0];
}
return fieldValues;
},
parseGeoKeyDirectory: function(fileDirectory) {
var rawGeoKeyDirectory = fileDirectory.GeoKeyDirectory;
if (!rawGeoKeyDirectory) {
return null;
}
var geoKeyDirectory = {};
for (var i = 4; i < rawGeoKeyDirectory[3] * 4; i += 4) {
var key = geoKeyNames[rawGeoKeyDirectory[i]],
location = (rawGeoKeyDirectory[i+1]) ? (fieldTagNames[rawGeoKeyDirectory[i+1]]) : null,
count = rawGeoKeyDirectory[i+2],
offset = rawGeoKeyDirectory[i+3];
var value = null;
if (!location) {
value = offset;
}
else {
value = fileDirectory[location];
if (typeof value === "undefined" || value === null) {
throw new Error("Could not get value of geoKey '" + key + "'.");
}
else if (typeof value === "string") {
value = value.substring(offset, offset + count - 1);
}
else if (value.subarray) {
value = value.subarray(offset, offset + count - 1);
}
}
geoKeyDirectory[key] = value;
}
return geoKeyDirectory;
},
parseFileDirectories: function(byteOffset) {
var nextIFDByteOffset = byteOffset;
var fileDirectories = [];
while (nextIFDByteOffset !== 0x00000000) {
var numDirEntries = this.bigTiff ?
this.dataView.getUint64(nextIFDByteOffset, this.littleEndian) :
this.dataView.getUint16(nextIFDByteOffset, this.littleEndian);
var fileDirectory = {};
var i = nextIFDByteOffset + (this.bigTiff ? 8 : 2);
for (var entryCount = 0; entryCount < numDirEntries; i += (this.bigTiff ? 20 : 12), ++entryCount) {
var fieldTag = this.dataView.getUint16(i, this.littleEndian);
var fieldType = this.dataView.getUint16(i + 2, this.littleEndian);
var typeCount = this.bigTiff ?
this.dataView.getUint64(i + 4, this.littleEndian):
this.dataView.getUint32(i + 4, this.littleEndian);
fileDirectory[fieldTagNames[fieldTag]] = this.getFieldValues(
fieldTag, fieldType, typeCount, i + (this.bigTiff ? 12 : 8)
);
}
fileDirectories.push([
fileDirectory, this.parseGeoKeyDirectory(fileDirectory)
]);
nextIFDByteOffset = this.getOffset(i);
}
return fileDirectories;
},
/**
* Get the n-th internal subfile a an image. By default, the first is returned.
*
* @param {Number} [index=0] the index of the image to return.
* @returns {GeoTIFFImage} the image at the given index
*/
getImage: function(index) {
index = index || 0;
var fileDirectoryAndGeoKey = this.fileDirectories[index];
if (!fileDirectoryAndGeoKey) {
throw new RangeError("Invalid image index");
}
return new GeoTIFFImage(fileDirectoryAndGeoKey[0], fileDirectoryAndGeoKey[1], this.dataView, this.littleEndian, this.cache);
},
/**
* Returns the count of the internal subfiles.
*
* @returns {Number} the number of internal subfile images
*/
getImageCount: function() {
return this.fileDirectories.length;
}
};
module.exports = GeoTIFF;