89 lines
2.2 KiB
Plaintext
89 lines
2.2 KiB
Plaintext
// Utils used to parse miaf-based files (avif/heic/heif)
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//
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// - image collections are not supported (only last size is reported)
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// - images with metadata encoded after image data are not supported
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// - images without any `ispe` box are not supported
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//
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/* eslint-disable consistent-return */
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'use strict';
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var str2arr = require('../common').str2arr;
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var sliceEq = require('../common').sliceEq;
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var readUInt32BE = require('../common').readUInt32BE;
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var miaf = require('../miaf_utils');
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var exif = require('../exif_utils');
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var SIG_FTYP = str2arr('ftyp');
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module.exports = function (data) {
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// ISO media file (avif format) starts with ftyp box:
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// 0000 0020 6674 7970 6176 6966
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// (length) f t y p a v i f
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//
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if (!sliceEq(data, 4, SIG_FTYP)) return;
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var firstBox = miaf.unbox(data, 0);
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if (!firstBox) return;
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var fileType = miaf.getMimeType(firstBox.data);
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if (!fileType) return;
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var meta, offset = firstBox.end;
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for (;;) {
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var box = miaf.unbox(data, offset);
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if (!box) break;
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offset = box.end;
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// mdat block SHOULD be last (but not strictly required),
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// so it's unlikely that metadata is after it
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if (box.boxtype === 'mdat') return;
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if (box.boxtype === 'meta') {
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meta = box.data;
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break;
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}
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}
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if (!meta) return;
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var imgSize = miaf.readSizeFromMeta(meta);
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if (!imgSize) return;
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var result = {
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width: imgSize.width,
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height: imgSize.height,
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type: fileType.type,
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mime: fileType.mime,
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wUnits: 'px',
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hUnits: 'px'
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};
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if (imgSize.variants.length > 1) {
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result.variants = imgSize.variants;
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}
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if (imgSize.orientation) {
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result.orientation = imgSize.orientation;
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}
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if (imgSize.exif_location &&
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imgSize.exif_location.offset + imgSize.exif_location.length <= data.length) {
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var sig_offset = readUInt32BE(data, imgSize.exif_location.offset);
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var exif_data = data.slice(
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imgSize.exif_location.offset + sig_offset + 4,
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imgSize.exif_location.offset + imgSize.exif_location.length);
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var orientation = exif.get_orientation(exif_data);
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if (orientation > 0) result.orientation = orientation;
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}
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return result;
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};
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