1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 // TODO:(kaznacheev) Share the EXIF constants with exif_parser.js
6 var EXIF_MARK_SOS = 0xffda; // Start of "stream" (the actual image data).
7 var EXIF_MARK_SOI = 0xffd8; // Start of image data.
8 var EXIF_MARK_EOI = 0xffd9; // End of image data.
10 var EXIF_MARK_APP0 = 0xffe0; // APP0 block, most commonly JFIF data.
11 var EXIF_MARK_EXIF = 0xffe1; // Start of exif block.
13 var EXIF_ALIGN_LITTLE = 0x4949; // Indicates little endian exif data.
14 var EXIF_ALIGN_BIG = 0x4d4d; // Indicates big endian exif data.
16 var EXIF_TAG_TIFF = 0x002a; // First directory containing TIFF data.
17 var EXIF_TAG_GPSDATA = 0x8825; // Pointer from TIFF to the GPS directory.
18 var EXIF_TAG_EXIFDATA = 0x8769; // Pointer from TIFF to the EXIF IFD.
20 var EXIF_TAG_JPG_THUMB_OFFSET = 0x0201; // Pointer from TIFF to thumbnail.
21 var EXIF_TAG_JPG_THUMB_LENGTH = 0x0202; // Length of thumbnail data.
23 var EXIF_TAG_IMAGE_WIDTH = 0x0100;
24 var EXIF_TAG_IMAGE_HEIGHT = 0x0101;
26 var EXIF_TAG_ORIENTATION = 0x0112;
27 var EXIF_TAG_X_DIMENSION = 0xA002;
28 var EXIF_TAG_Y_DIMENSION = 0xA003;
31 * The Exif metadata encoder.
32 * Uses the metadata format as defined by ExifParser.
33 * @param {Object} original_metadata Metadata to encode.
35 * @extends {ImageEncoder.MetadataEncoder}
37 function ExifEncoder(original_metadata) {
38 ImageEncoder.MetadataEncoder.apply(this, arguments);
40 this.ifd_ = this.metadata_.ifd;
42 this.ifd_ = this.metadata_.ifd = {};
45 ExifEncoder.prototype = {__proto__: ImageEncoder.MetadataEncoder.prototype};
47 ImageEncoder.registerMetadataEncoder(ExifEncoder, 'image/jpeg');
50 * @param {HTMLCanvasElement|Object} canvas Canvas or anything with
51 * width and height properties.
53 ExifEncoder.prototype.setImageData = function(canvas) {
54 var image = this.ifd_.image;
56 image = this.ifd_.image = {};
58 // Only update width/height in this directory if they are present.
59 if (image[EXIF_TAG_IMAGE_WIDTH] && image[EXIF_TAG_IMAGE_HEIGHT]) {
60 image[EXIF_TAG_IMAGE_WIDTH].value = canvas.width;
61 image[EXIF_TAG_IMAGE_HEIGHT].value = canvas.height;
64 var exif = this.ifd_.exif;
66 exif = this.ifd_.exif = {};
67 ExifEncoder.findOrCreateTag(image, EXIF_TAG_EXIFDATA);
68 ExifEncoder.findOrCreateTag(exif, EXIF_TAG_X_DIMENSION).value = canvas.width;
69 ExifEncoder.findOrCreateTag(exif, EXIF_TAG_Y_DIMENSION).value = canvas.height;
71 this.metadata_.width = canvas.width;
72 this.metadata_.height = canvas.height;
74 // Always save in default orientation.
75 delete this.metadata_.imageTransform;
76 ExifEncoder.findOrCreateTag(image, EXIF_TAG_ORIENTATION).value = 1;
81 * @param {HTMLCanvasElement} canvas Thumbnail canvas.
82 * @param {number} quality (0..1] Thumbnail encoding quality.
84 ExifEncoder.prototype.setThumbnailData = function(canvas, quality) {
85 // Empirical formula with reasonable behavior:
86 // 10K for 1Mpix, 30K for 5Mpix, 50K for 9Mpix and up.
87 var pixelCount = this.metadata_.width * this.metadata_.height;
88 var maxEncodedSize = 5000 * Math.min(10, 1 + pixelCount / 1000000);
90 var DATA_URL_PREFIX = 'data:' + this.mimeType + ';base64,';
91 var BASE64_BLOAT = 4 / 3;
92 var maxDataURLLength =
93 DATA_URL_PREFIX.length + Math.ceil(maxEncodedSize * BASE64_BLOAT);
95 for (;; quality *= 0.8) {
96 ImageEncoder.MetadataEncoder.prototype.setThumbnailData.call(
97 this, canvas, quality);
98 if (this.metadata_.thumbnailURL.length <= maxDataURLLength || quality < 0.2)
102 if (this.metadata_.thumbnailURL.length <= maxDataURLLength) {
103 var thumbnail = this.ifd_.thumbnail;
105 thumbnail = this.ifd_.thumbnail = {};
107 ExifEncoder.findOrCreateTag(thumbnail, EXIF_TAG_IMAGE_WIDTH).value =
110 ExifEncoder.findOrCreateTag(thumbnail, EXIF_TAG_IMAGE_HEIGHT).value =
113 // The values for these tags will be set in ExifWriter.encode.
114 ExifEncoder.findOrCreateTag(thumbnail, EXIF_TAG_JPG_THUMB_OFFSET);
115 ExifEncoder.findOrCreateTag(thumbnail, EXIF_TAG_JPG_THUMB_LENGTH);
117 // Always save in default orientation.
118 ExifEncoder.findOrCreateTag(thumbnail, EXIF_TAG_ORIENTATION).value = 1;
121 'Thumbnail URL too long: ' + this.metadata_.thumbnailURL.length);
122 // Delete thumbnail ifd so that it is not written out to a file, but
123 // keep thumbnailURL for display purposes.
124 if (this.ifd_.thumbnail) {
125 delete this.ifd_.thumbnail;
128 delete this.metadata_.thumbnailTransform;
132 * Return a range where the metadata is (or should be) located.
133 * @param {string} encodedImage Raw image data to look for metadata.
134 * @return {Object} An object with from and to properties.
136 ExifEncoder.prototype.findInsertionRange = function(encodedImage) {
137 function getWord(pos) {
138 if (pos + 2 > encodedImage.length)
139 throw 'Reading past the buffer end @' + pos;
140 return encodedImage.charCodeAt(pos) << 8 | encodedImage.charCodeAt(pos + 1);
143 if (getWord(0) != EXIF_MARK_SOI)
144 throw new Error('Jpeg data starts from 0x' + getWord(0).toString(16));
146 var sectionStart = 2;
148 // Default: an empty range right after SOI.
149 // Will be returned in absence of APP0 or Exif sections.
150 var range = {from: sectionStart, to: sectionStart};
153 var tag = getWord(sectionStart);
155 if (tag == EXIF_MARK_SOS)
158 var nextSectionStart = sectionStart + 2 + getWord(sectionStart + 2);
159 if (nextSectionStart <= sectionStart ||
160 nextSectionStart > encodedImage.length)
161 throw new Error('Invalid section size in jpeg data');
163 if (tag == EXIF_MARK_APP0) {
164 // Assert that we have not seen the Exif section yet.
165 if (range.from != range.to)
166 throw new Error('APP0 section found after EXIF section');
167 // An empty range right after the APP0 segment.
168 range.from = range.to = nextSectionStart;
169 } else if (tag == EXIF_MARK_EXIF) {
170 // A range containing the existing EXIF section.
171 range.from = sectionStart;
172 range.to = nextSectionStart;
174 sectionStart = nextSectionStart;
181 * @return {ArrayBuffer} serialized metadata ready to write to an image file.
183 ExifEncoder.prototype.encode = function() {
184 var HEADER_SIZE = 10;
186 // Allocate the largest theoretically possible size.
187 var bytes = new Uint8Array(0x10000);
190 var hw = new ByteWriter(bytes.buffer, 0, HEADER_SIZE);
191 hw.writeScalar(EXIF_MARK_EXIF, 2);
192 hw.forward('size', 2);
193 hw.writeString('Exif\0\0'); // Magic string.
195 // First serialize the content of the exif section.
196 // Use a ByteWriter starting at HEADER_SIZE offset so that tell() positions
197 // can be directly mapped to offsets as encoded in the dictionaries.
198 var bw = new ByteWriter(bytes.buffer, HEADER_SIZE);
200 if (this.metadata_.littleEndian) {
201 bw.setByteOrder(ByteWriter.LITTLE_ENDIAN);
202 bw.writeScalar(EXIF_ALIGN_LITTLE, 2);
204 bw.setByteOrder(ByteWriter.BIG_ENDIAN);
205 bw.writeScalar(EXIF_ALIGN_BIG, 2);
208 bw.writeScalar(EXIF_TAG_TIFF, 2);
210 bw.forward('image-dir', 4); // The pointer should point right after itself.
211 bw.resolveOffset('image-dir');
213 ExifEncoder.encodeDirectory(bw, this.ifd_.image,
214 [EXIF_TAG_EXIFDATA, EXIF_TAG_GPSDATA], 'thumb-dir');
216 if (this.ifd_.exif) {
217 bw.resolveOffset(EXIF_TAG_EXIFDATA);
218 ExifEncoder.encodeDirectory(bw, this.ifd_.exif);
220 if (EXIF_TAG_EXIFDATA in this.ifd_.image)
221 throw new Error('Corrupt exif dictionary reference');
225 bw.resolveOffset(EXIF_TAG_GPSDATA);
226 ExifEncoder.encodeDirectory(bw, this.ifd_.gps);
228 if (EXIF_TAG_GPSDATA in this.ifd_.image)
229 throw new Error('Missing gps dictionary reference');
232 if (this.ifd_.thumbnail) {
233 bw.resolveOffset('thumb-dir');
234 ExifEncoder.encodeDirectory(
237 [EXIF_TAG_JPG_THUMB_OFFSET, EXIF_TAG_JPG_THUMB_LENGTH]);
239 var thumbnailDecoded =
240 ImageEncoder.decodeDataURL(this.metadata_.thumbnailURL);
241 bw.resolveOffset(EXIF_TAG_JPG_THUMB_OFFSET);
242 bw.resolve(EXIF_TAG_JPG_THUMB_LENGTH, thumbnailDecoded.length);
243 bw.writeString(thumbnailDecoded);
245 bw.resolve('thumb-dir', 0);
250 var totalSize = HEADER_SIZE + bw.tell();
251 hw.resolve('size', totalSize - 2); // The marker is excluded.
254 var subarray = new Uint8Array(totalSize);
255 for (var i = 0; i != totalSize; i++) {
256 subarray[i] = bytes[i];
258 return subarray.buffer;
266 * Write the contents of an IFD directory.
267 * @param {ByteWriter} bw ByteWriter to use.
268 * @param {Object} directory A directory map as created by ExifParser.
269 * @param {Array} resolveLater An array of tag ids for which the values will be
271 * @param {string} nextDirPointer A forward key for the pointer to the next
272 * directory. If omitted the pointer is set to 0.
274 ExifEncoder.encodeDirectory = function(
275 bw, directory, resolveLater, nextDirPointer) {
279 bw.forward('dir-count', 2);
282 for (var key in directory) {
283 var tag = directory[key];
284 bw.writeScalar(tag.id, 2);
285 bw.writeScalar(tag.format, 2);
286 bw.writeScalar(tag.componentCount, 4);
288 var width = ExifEncoder.getComponentWidth(tag) * tag.componentCount;
290 if (resolveLater && (resolveLater.indexOf(tag.id) >= 0)) {
291 // The actual value depends on further computations.
292 if (tag.componentCount != 1 || width > 4)
293 throw new Error('Cannot forward the pointer for ' + tag.id);
294 bw.forward(tag.id, width);
295 } else if (width <= 4) {
296 // The value fits into 4 bytes, write it immediately.
297 ExifEncoder.writeValue(bw, tag);
299 // The value does not fit, forward the 4 byte offset to the actual value.
301 bw.forward(tag.id, width);
302 longValues.push(tag);
304 bw.skip(4 - width); // Align so that the value take up exactly 4 bytes.
308 bw.resolve('dir-count', count);
310 if (nextDirPointer) {
311 bw.forward(nextDirPointer, 4);
313 bw.writeScalar(0, 4);
316 // Write out the long values and resolve pointers.
317 for (var i = 0; i != longValues.length; i++) {
318 var longValue = longValues[i];
319 bw.resolveOffset(longValue.id);
320 ExifEncoder.writeValue(bw, longValue);
325 * @param {{format:number, id:number}} tag EXIF tag object.
326 * @return {number} Width in bytes of the data unit associated with this tag.
327 * TODO(kaznacheev): Share with ExifParser?
329 ExifEncoder.getComponentWidth = function(tag) {
330 switch (tag.format) {
340 case 9: // Signed Long
344 case 10: // Signed Rational
348 console.warn('Unknown tag format 0x' +
349 Number(tag.id).toString(16) + ': ' + tag.format);
355 * Writes out the tag value.
356 * @param {ByteWriter} bw Writer to use.
357 * @param {Object} tag Tag, which value to write.
359 ExifEncoder.writeValue = function(bw, tag) {
360 if (tag.format == 2) { // String
361 if (tag.componentCount != tag.value.length) {
363 'String size mismatch for 0x' + Number(tag.id).toString(16));
365 bw.writeString(tag.value);
366 } else { // Scalar or rational
367 var width = ExifEncoder.getComponentWidth(tag);
369 var writeComponent = function(value, signed) {
371 bw.writeScalar(value[0], 4, signed);
372 bw.writeScalar(value[1], 4, signed);
374 bw.writeScalar(value, width, signed);
378 var signed = (tag.format == 9 || tag.format == 10);
379 if (tag.componentCount == 1) {
380 writeComponent(tag.value, signed);
382 for (var i = 0; i != tag.componentCount; i++) {
383 writeComponent(tag.value[i], signed);
390 * @param {{Object.<number,Object>}} directory EXIF directory.
391 * @param {number} id Tag id.
392 * @param {number} format Tag format
393 * (used in {@link ExifEncoder#getComponentWidth}).
394 * @param {number} componentCount Number of components in this tag.
395 * @return {{id:number, format:number, componentCount:number}}
396 * Tag found or created.
398 ExifEncoder.findOrCreateTag = function(directory, id, format, componentCount) {
399 if (!(id in directory)) {
402 format: format || 3, // Short
403 componentCount: componentCount || 1
406 return directory[id];
411 * @param {ArrayBuffer} arrayBuffer Underlying buffer to use.
412 * @param {number} offset Offset at which to start writing.
413 * @param {number} length Maximum length to use.
417 function ByteWriter(arrayBuffer, offset, length) {
418 length = length || (arrayBuffer.byteLength - offset);
419 this.view_ = new DataView(arrayBuffer, offset, length);
420 this.littleEndian_ = false;
426 * Little endian byte order.
429 ByteWriter.LITTLE_ENDIAN = 0;
432 * Bug endian byte order.
435 ByteWriter.BIG_ENDIAN = 1;
438 * Set the byte ordering for future writes.
439 * @param {number} order ByteOrder to use {ByteWriter.LITTLE_ENDIAN}
440 * or {ByteWriter.BIG_ENDIAN}.
442 ByteWriter.prototype.setByteOrder = function(order) {
443 this.littleEndian_ = (order == ByteWriter.LITTLE_ENDIAN);
447 * @return {number} the current write position.
449 ByteWriter.prototype.tell = function() { return this.pos_ };
452 * Skips desired amount of bytes in output stream.
453 * @param {number} count Byte count to skip.
455 ByteWriter.prototype.skip = function(count) {
456 this.validateWrite(count);
461 * Check if the buffer has enough room to read 'width' bytes. Throws an error
463 * @param {number} width Amount of bytes to check.
465 ByteWriter.prototype.validateWrite = function(width) {
466 if (this.pos_ + width > this.view_.byteLength)
467 throw new Error('Writing past the end of the buffer');
471 * Writes scalar value to output stream.
472 * @param {number} value Value to write.
473 * @param {number} width Desired width of written value.
474 * @param {boolean=} opt_signed True if value represents signed number.
476 ByteWriter.prototype.writeScalar = function(value, width, opt_signed) {
478 // The below switch is so verbose for two reasons:
479 // 1. V8 is faster on method names which are 'symbols'.
480 // 2. Method names are discoverable by full text search.
483 method = opt_signed ? 'setInt8' : 'setUint8';
487 method = opt_signed ? 'setInt16' : 'setUint16';
491 method = opt_signed ? 'setInt32' : 'setUint32';
495 method = opt_signed ? 'setInt64' : 'setUint64';
499 throw new Error('Invalid width: ' + width);
503 this.validateWrite(width);
504 this.view_[method](this.pos_, value, this.littleEndian_);
510 * @param {string} str String to write.
512 ByteWriter.prototype.writeString = function(str) {
513 this.validateWrite(str.length);
514 for (var i = 0; i != str.length; i++) {
515 this.view_.setUint8(this.pos_++, str.charCodeAt(i));
520 * Allocate the space for 'width' bytes for the value that will be set later.
521 * To be followed by a 'resolve' call with the same key.
522 * @param {string} key A key to identify the value.
523 * @param {number} width Width of the value in bytes.
525 ByteWriter.prototype.forward = function(key, width) {
526 if (key in this.forwards_)
527 throw new Error('Duplicate forward key ' + key);
528 this.validateWrite(width);
529 this.forwards_[key] = {
537 * Set the value previously allocated with a 'forward' call.
538 * @param {string} key A key to identify the value.
539 * @param {number} value value to write in pre-allocated space.
541 ByteWriter.prototype.resolve = function(key, value) {
542 if (!(key in this.forwards_))
543 throw new Error('Undeclared forward key ' + key.toString(16));
544 var forward = this.forwards_[key];
545 var curPos = this.pos_;
546 this.pos_ = forward.pos;
547 this.writeScalar(value, forward.width);
549 delete this.forwards_[key];
553 * A shortcut to resolve the value to the current write position.
554 * @param {string} key A key to identify pre-allocated position.
556 ByteWriter.prototype.resolveOffset = function(key) {
557 this.resolve(key, this.tell());
561 * Check if every forward has been resolved, throw and error if not.
563 ByteWriter.prototype.checkResolved = function() {
564 for (var key in this.forwards_) {
565 throw new Error('Unresolved forward pointer ' + key.toString(16));