From ce5433cbdca4e633f233fbddbdd020815a15a9c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maigret=20Aur=C3=A9lien?= <github@dewep.net>
Date: Tue, 21 Apr 2020 16:59:02 +0200
Subject: [PATCH] feat(decode): add tolerantDecoding option (#57)

---
 index.d.ts     |  6 ++++--
 lib/decoder.js | 16 +++++++++++++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index 7e49ba2..6f27b79 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -20,9 +20,11 @@ export declare function decode(jpegData: BufferLike, opts?: false): BufferRet;
 
 export declare function decode(jpegData: BufferLike, opts: {
   useTArray: true,
-  colorTransform?: boolean
+  colorTransform?: boolean,
+  tolerantDecoding?: boolean
 }): UintArrRet;
 export declare function decode(jpegData: BufferLike, opts?: {
   useTArray?: false,
-  colorTransform?: boolean
+  colorTransform?: boolean,
+  tolerantDecoding?: boolean
 }): BufferRet;
diff --git a/lib/decoder.js b/lib/decoder.js
index 2f120ed..cac42f1 100644
--- a/lib/decoder.js
+++ b/lib/decoder.js
@@ -93,7 +93,7 @@ var JpegImage = (function jpegImage() {
   function decodeScan(data, offset,
                       frame, components, resetInterval,
                       spectralStart, spectralEnd,
-                      successivePrev, successive) {
+                      successivePrev, successive, opts) {
     var precision = frame.precision;
     var samplesPerLine = frame.samplesPerLine;
     var scanLines = frame.scanLines;
@@ -258,11 +258,17 @@ var JpegImage = (function jpegImage() {
       var mcuCol = mcu % mcusPerLine;
       var blockRow = mcuRow * component.v + row;
       var blockCol = mcuCol * component.h + col;
+      // If the block is missing and we're in tolerant mode, just skip it.
+      if (component.blocks[blockRow] === undefined && opts.tolerantDecoding)
+        return;
       decode(component, component.blocks[blockRow][blockCol]);
     }
     function decodeBlock(component, decode, mcu) {
       var blockRow = (mcu / component.blocksPerLine) | 0;
       var blockCol = mcu % component.blocksPerLine;
+      // If the block is missing and we're in tolerant mode, just skip it.
+      if (component.blocks[blockRow] === undefined && opts.tolerantDecoding)
+        return;
       decode(component, component.blocks[blockRow][blockCol]);
     }
 
@@ -746,7 +752,7 @@ var JpegImage = (function jpegImage() {
             var processed = decodeScan(data, offset,
               frame, components, resetInterval,
               spectralStart, spectralEnd,
-              successiveApproximation >> 4, successiveApproximation & 15);
+              successiveApproximation >> 4, successiveApproximation & 15, this.opts);
             offset += processed;
             break;
 
@@ -990,7 +996,8 @@ function decode(jpegData, opts) {
     useTArray: false,
     // "undefined" means "Choose whether to transform colors based on the image’s color model."
     colorTransform: undefined,
-    formatAsRGBA: true
+    formatAsRGBA: true,
+    tolerantDecoding: false
   };
   if (opts) {
     if (typeof opts === 'object') {
@@ -999,6 +1006,8 @@ function decode(jpegData, opts) {
                     defaultOpts.useTArray : opts.useTArray),
         colorTransform: (typeof opts.colorTransform === 'undefined' ?
                          defaultOpts.colorTransform : opts.colorTransform),
+        tolerantDecoding: (typeof opts.tolerantDecoding === 'undefined' ?
+                           defaultOpts.tolerantDecoding : opts.tolerantDecoding),
         formatAsRGBA: (typeof opts.formatAsRGBA === 'undefined' ?
                          defaultOpts.formatAsRGBA : opts.formatAsRGBA)
       };
@@ -1013,6 +1022,7 @@ function decode(jpegData, opts) {
 
   var arr = new Uint8Array(jpegData);
   var decoder = new JpegImage();
+  decoder.opts = opts;
   decoder.parse(arr);
   decoder.colorTransform = opts.colorTransform;