From e5c829b38ccaee353cfeca412f17bbd079b593e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Konstantin=20K=C3=A4fer?= <mail@kkaefer.com>
Date: Wed, 20 Jan 2016 16:42:16 +0100
Subject: [Qt] use libjpeg-turbo rather than Qt's built-in JPEG decoding

libjpeg-turbo is typically 2-4x faster than the built-in decoding.
---
 platform/qt/platform.gyp         | 4 ++++
 platform/qt/scripts/configure.sh | 1 +
 platform/qt/src/image.cpp        | 9 +++++++++
 3 files changed, 14 insertions(+)

diff --git a/platform/qt/platform.gyp b/platform/qt/platform.gyp
index 10f69c4a61..fb73c00ce1 100644
--- a/platform/qt/platform.gyp
+++ b/platform/qt/platform.gyp
@@ -34,6 +34,7 @@
       'sources': [
         '../default/asset_file_source.cpp',
         '../default/default_file_source.cpp',
+        '../default/jpeg_reader.cpp',
         '../default/log_stderr.cpp',
         '../default/mbgl/storage/offline.cpp',
         '../default/mbgl/storage/offline_database.cpp',
@@ -65,6 +66,7 @@
       'variables': {
         'cflags': [
           '<@(boost_cflags)',
+          '<@(libjpeg-turbo_cflags)',
           '<@(nunicode_cflags)',
           '<@(opengl_cflags)',
           '<@(qt_cflags)',
@@ -76,6 +78,7 @@
           '-fPIC',
         ],
         'ldflags': [
+          '<@(libjpeg-turbo_ldflags)',
           '<@(nunicode_ldflags)',
           '<@(opengl_ldflags)',
           '<@(qt_ldflags)',
@@ -86,6 +89,7 @@
         'libraries': [
           '<@(nunicode_static_libs)',
           '<@(sqlite_static_libs)',
+          '<@(libjpeg-turbo_static_libs)',
           '<@(webp_static_libs)',
           '<@(zlib_static_libs)',
         ],
diff --git a/platform/qt/scripts/configure.sh b/platform/qt/scripts/configure.sh
index 164598e6ff..66ee7f1471 100644
--- a/platform/qt/scripts/configure.sh
+++ b/platform/qt/scripts/configure.sh
@@ -3,6 +3,7 @@
 BOOST_VERSION=1.59.0
 GEOJSONVT_VERSION=4.1.2
 GTEST_VERSION=1.7.0
+LIBJPEG_TURBO_VERSION=1.4.2
 NUNICODE_VERSION=1.6
 PIXELMATCH_VERSION=0.9.0
 RAPIDJSON_VERSION=1.0.2
diff --git a/platform/qt/src/image.cpp b/platform/qt/src/image.cpp
index 96a5eb0eed..816b3d7aee 100644
--- a/platform/qt/src/image.cpp
+++ b/platform/qt/src/image.cpp
@@ -19,6 +19,7 @@ std::string encodePNG(const PremultipliedImage& pre) {
     return std::string(array.constData(), array.size());
 }
 
+PremultipliedImage decodeJPEG(const uint8_t*, size_t);
 PremultipliedImage decodeWebP(const uint8_t*, size_t);
 
 PremultipliedImage decodeImage(const std::string& string) {
@@ -34,6 +35,14 @@ PremultipliedImage decodeImage(const std::string& string) {
         }
     }
 
+    // Use libjpeg-turbo rather than the built-in version of libjpeg.
+    if (size >= 2) {
+        uint16_t magic = ((data[0] << 8) | data[1]) & 0xffff;
+        if (magic == 0xFFD8) {
+            return decodeJPEG(data, size);
+        }
+    }
+
     QImage image =
         QImage::fromData(data, size)
         .rgbSwapped()
-- 
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