Add support for JPEG-LS (.jls) (#568)

Author: Borewit

core.d.ts

@@ -140,7 +140,8 @@ export type FileExtension =
 	| '3mf'
 	| 'zst'
 	| 'jxl'
-	| 'vcf';
+	| 'vcf'
+	| 'jls';
 
 export type MimeType =
 	| 'image/jpeg'
@@ -276,7 +277,8 @@ export type MimeType =
 	| 'application/vnd.ms-htmlhelp'
 	| 'model/3mf'
 	| 'image/jxl'
-	| 'application/zstd';
+	| 'application/zstd'
+	| 'image/jls';
 
 export type FileTypeResult = {
 	/**

core.js

@@ -159,13 +159,6 @@ class FileTypeParser {
 			};
 		}
 
-		if (this.check([0xFF, 0xD8, 0xFF])) {
-			return {
-				ext: 'jpg',
-				mime: 'image/jpeg',
-			};
-		}
-
 		if (this.check([0x49, 0x49, 0xBC])) {
 			return {
 				ext: 'jxr',
@@ -222,6 +215,21 @@ class FileTypeParser {
 
 		// -- 4-byte signatures --
 
+		// Requires a sample size of 4 bytes
+		if (this.check([0xFF, 0xD8, 0xFF])) {
+			if (this.check([0xF7], {offset: 3})) { // JPG7/SOF55, indicating a ISO/IEC 14495 / JPEG-LS file
+				return {
+					ext: 'jls',
+					mime: 'image/jls',
+				};
+			}
+
+			return {
+				ext: 'jpg',
+				mime: 'image/jpeg',
+			};
+		}
+
 		if (this.checkString('FLIF')) {
 			return {
 				ext: 'flif',

fixture/fixture-hp1.jls

@@ -193,7 +193,8 @@
 		"3mf",
 		"zst",
 		"jxl",
-		"vcf"
+		"vcf",
+		"jls"
 	],
 	"dependencies": {
 		"readable-web-to-node-stream": "^3.0.2",

fixture/fixture-hp2.jls

@@ -397,6 +397,7 @@ Returns a `Set<string>` of supported MIME types.
 - [`ics`](https://en.wikipedia.org/wiki/ICalendar#Data_format) - iCalendar
 - [`indd`](https://en.wikipedia.org/wiki/Adobe_InDesign#File_format) - Adobe InDesign document
 - [`it`](https://wiki.openmpt.org/Manual:_Module_formats#The_Impulse_Tracker_format_.28.it.29) - Audio module format: Impulse Tracker
+- [`jls`](https://en.wikipedia.org/wiki/Lossless_JPEG#JPEG-LS) - Lossless/near-lossless compression standard for continuous-tone images
 - [`jp2`](https://en.wikipedia.org/wiki/JPEG_2000) - JPEG 2000
 - [`jpg`](https://en.wikipedia.org/wiki/JPEG) - Joint Photographic Experts Group image
 - [`jpm`](https://en.wikipedia.org/wiki/JPEG_2000) - JPEG 2000

fixture/fixture-hp3.jls

@@ -138,6 +138,7 @@ export const extensions = [
 	'zst',
 	'jxl',
 	'vcf',
+	'jls',
 ];
 
 export const mimeTypes = [
@@ -275,4 +276,5 @@ export const mimeTypes = [
 	'model/3mf',
 	'image/jxl',
 	'application/zstd',
+	'image/jls',
 ];

fixture/fixture-normal.jls

@@ -229,6 +229,12 @@ const names = {
 		'fixture-utf16-be-bom', // UTF-16 little endian encoded XML, with BOM
 		'fixture-utf16-le-bom', // UTF-16 big endian encoded XML, with BOM
 	],
+	jls: [
+		'fixture-normal',
+		'fixture-hp1',
+		'fixture-hp2',
+		'fixture-hp3',
+	],
 };
 
 // Define an entry here only if the file type has potential