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List:       kde-commits
Subject:    [digikam] libs/dimg/loaders: correct chroma subsampling in JPEGLoader and adds a chroma subsampling 
From:       Maik Qualmann <metzpinguin () gmail ! com>
Date:       2016-01-31 20:02:32
Message-ID: E1aPyCe-00015o-TR () scm ! kde ! org
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Git commit b5be6c56a43af98a639e2668ff99d8a47fd6504a by Maik Qualmann.
Committed on 31/01/2016 at 20:01.
Pushed by mqualmann into branch 'master'.

correct chroma subsampling in JPEGLoader and adds a chroma subsampling mode

M  +16   -4    libs/dimg/loaders/jpegloader.cpp
M  +12   -8    libs/dimg/loaders/jpegsettings.cpp

http://commits.kde.org/digikam/b5be6c56a43af98a639e2668ff99d8a47fd6504a

diff --git a/libs/dimg/loaders/jpegloader.cpp b/libs/dimg/loaders/jpegloader.cpp
index c33d785..f33c15c 100644
--- a/libs/dimg/loaders/jpegloader.cpp
+++ b/libs/dimg/loaders/jpegloader.cpp
@@ -736,9 +736,9 @@ bool JPEGLoader::save(const QString& filePath, \
DImgLoaderObserver* const observe  
     switch (subsampling)
     {
-        case 1:  // 2x1, 1x1, 1x1 (4:2:2) : Medium
+        case 1:  // 2x1, 1x1, 1x1 (4:2:2) : Low
         {
-            qCDebug(DIGIKAM_DIMG_LOG_JPEG) << "Using LibJPEG medium \
chroma-subsampling (4:2:2)"; +            qCDebug(DIGIKAM_DIMG_LOG_JPEG) << "Using \
LibJPEG low chroma-subsampling (4:2:2)";  cinfo.comp_info[0].h_samp_factor = 2;
             cinfo.comp_info[0].v_samp_factor = 1;
             cinfo.comp_info[1].h_samp_factor = 1;
@@ -748,9 +748,9 @@ bool JPEGLoader::save(const QString& filePath, \
DImgLoaderObserver* const observe  break;
         }
 
-        case 2:  // 2x2, 1x1, 1x1 (4:1:1) : High
+        case 2:  // 2x2, 1x1, 1x1 (4:2:0) : Medium
         {
-            qCDebug(DIGIKAM_DIMG_LOG_JPEG) << "Using LibJPEG high chroma-subsampling \
(4:1:1)"; +            qCDebug(DIGIKAM_DIMG_LOG_JPEG) << "Using LibJPEG medium \
chroma-subsampling (4:2:0)";  cinfo.comp_info[0].h_samp_factor = 2;
             cinfo.comp_info[0].v_samp_factor = 2;
             cinfo.comp_info[1].h_samp_factor = 1;
@@ -760,6 +760,18 @@ bool JPEGLoader::save(const QString& filePath, \
DImgLoaderObserver* const observe  break;
         }
 
+        case 3:  // 4x1, 1x1, 1x1 (4:1:1) : High
+        {
+            qCDebug(DIGIKAM_DIMG_LOG_JPEG) << "Using LibJPEG high chroma-subsampling \
(4:1:1)"; +            cinfo.comp_info[0].h_samp_factor = 4;
+            cinfo.comp_info[0].v_samp_factor = 1;
+            cinfo.comp_info[1].h_samp_factor = 1;
+            cinfo.comp_info[1].v_samp_factor = 1;
+            cinfo.comp_info[2].h_samp_factor = 1;
+            cinfo.comp_info[2].v_samp_factor = 1;
+            break;
+        }
+
         default:  // 1x1 1x1 1x1 (4:4:4) : None
         {
             qCDebug(DIGIKAM_DIMG_LOG_JPEG) << "Using LibJPEG none chroma-subsampling \
                (4:4:4)";
diff --git a/libs/dimg/loaders/jpegsettings.cpp b/libs/dimg/loaders/jpegsettings.cpp
index b93bfba..afa4beb 100644
--- a/libs/dimg/loaders/jpegsettings.cpp
+++ b/libs/dimg/loaders/jpegsettings.cpp
@@ -108,18 +108,22 @@ JPEGSettings::JPEGSettings(QWidget* const parent)
 
     d->subSamplingCB = new QComboBox(this);
     d->subSamplingCB->insertItem(0, i18n("None"));    // 1x1, 1x1, 1x1 (4:4:4)
-    d->subSamplingCB->insertItem(1, i18n("Medium"));  // 2x1, 1x1, 1x1 (4:2:2)
-    d->subSamplingCB->insertItem(2, i18n("High"));    // 2x2, 1x1, 1x1 (4:1:1)
+    d->subSamplingCB->insertItem(1, i18n("Low"));     // 2x1, 1x1, 1x1 (4:2:2)
+    d->subSamplingCB->insertItem(2, i18n("Medium"));  // 2x2, 1x1, 1x1 (4:2:0)
+    d->subSamplingCB->insertItem(3, i18n("High"));    // 4x1, 1x1, 1x1 (4:1:1)
     d->subSamplingCB->setWhatsThis(i18n("<p>JPEG Chroma subsampling level \n(color \
is saved with less resolution "  "than luminance):</p>"
                                         "<p><b>None</b>=best: uses 4:4:4 ratio. Does \
                not employ chroma "
                                         "subsampling at all. This preserves edges \
                and contrasting "
-                                        "colors, whilst adding no additional \
                compression</p>"
-                                        "<p><b>Medium</b>: uses 4:2:2 ratio. Medium \
                compression: reduces "
-                                        "the color resolution by one-third with \
                little to "
-                                        "no visual difference</p>"
-                                        "<p><b>High</b>: use 4:1:1 ratio. High \
                compression: suits "
-                                        "images with soft edges but tends to alter \
colors</p>" +                                        "colors, whilst adding no \
additional compression.</p>" +                                        "<p><b>Low</b>: \
uses 4:2:2 ratio. Low compression: reduces " +                                        \
"the horizontal color resolution by half with little to " +                           \
"no visual difference.</p>" +                                        \
"<p><b>Medium</b>: uses 4:2:0 ratio. Medium compression: reduces " +                  \
"the horizontal and vertical color resolution by half.</p>" +                         \
"<p><b>High</b>: use 4:1:1 ratio. High compression: reduces " +                       \
"the horizontal color resolution by one quarter. Created " +                          \
                "images with soft edges but tends to alter colors.</p>"
                                         "<p><b>Note: JPEG always uses lossy \
compression.</b></p>"));  
     d->JPEGGrid->addWidget(d->labelJPEGcompression, 0, 0, 1, 2);


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