Decode compressed zTXt, tEXt tags using latin1 encoding

They are always latin1 according to the specification. #324
mattiasw · May 29, 2024 · f481093 · f481093
1 parent bd8b13e
commit f481093
Show file tree

Hide file tree

Showing 5 changed files with 14 additions and 6 deletions.
diff --git a/dist/exif-reader.js b/dist/exif-reader.js
diff --git a/dist/exif-reader.js.map b/dist/exif-reader.js.map
diff --git a/src/icc-tags.js b/src/icc-tags.js
@@ -35,7 +35,7 @@ function readCompressedIcc(dataView, iccData) {
         return {};
     }
     const compressedDataView = new DataView(dataView.buffer.slice(iccData[0].offset, iccData[0].offset + iccData[0].length));
-    return decompress(compressedDataView, iccData[0].compressionMethod, 'dataview')
+    return decompress(compressedDataView, iccData[0].compressionMethod, 'utf-8', 'dataview')
         .then(parseTags)
         .catch(() => ({}));
 }

diff --git a/src/png-text-tags.js b/src/png-text-tags.js
@@ -106,7 +106,7 @@ function getNameAndValue(dataView, offset, length, type, async) {
     if (compressionMethod !== COMPRESSION_METHOD_NONE && !async) {
         return {};
     }
-    const decompressedValueChars = decompress(valueChars, compressionMethod);
+    const decompressedValueChars = decompress(valueChars, compressionMethod, getEncodingFromType(type));
     if (decompressedValueChars instanceof Promise) {
         return decompressedValueChars
             .then((_decompressedValueChars) => constructTag(_decompressedValueChars, type, langChars, keywordChars))
@@ -142,6 +142,13 @@ function moveToNextState(type, parsingState) {
     return STATE_TEXT;
 }
 
+function getEncodingFromType(type) {
+    if (type === TYPE_TEXT || type === TYPE_ZTXT) {
+        return 'latin1';
+    }
+    return 'utf-8';
+}
+
 function constructTag(valueChars, type, langChars, keywordChars) {
     const value = getValue(valueChars);
     return {

diff --git a/src/utils.js b/src/utils.js
@@ -150,15 +150,16 @@ export function strRepeat(string, num) {
 export const COMPRESSION_METHOD_NONE = undefined;
 export const COMPRESSION_METHOD_DEFLATE = 0;
 
-export function decompress(dataView, compressionMethod, returnType = 'string') {
+export function decompress(dataView, compressionMethod, encoding, returnType = 'string') {
     if (compressionMethod === COMPRESSION_METHOD_DEFLATE) {
         if (typeof DecompressionStream === 'function') {
             const decompressionStream = new DecompressionStream('deflate');
             const decompressedStream = new Blob([dataView]).stream().pipeThrough(decompressionStream);
             if (returnType === 'dataview') {
                 return new Response(decompressedStream).arrayBuffer().then((arrayBuffer) => new DataView(arrayBuffer));
             }
-            return new Response(decompressedStream).text();
+            return new Response(decompressedStream).arrayBuffer()
+                .then((buffer) => new TextDecoder(encoding).decode(buffer));
         }
     }
     if (compressionMethod !== undefined) {