diff --git a/imagescrollareagl.cpp b/imagescrollareagl.cpp
index f722a7e..52f0094 100644
--- a/imagescrollareagl.cpp
+++ b/imagescrollareagl.cpp
@@ -215,6 +215,18 @@ QVector2D ImageWidget::getImagePixelCoord(const QVector2D &pos)
     return (pos + offset) / m_scale;
 }
 
+void ImageWidget::setBayerMask(int mask)
+{
+    m_firstRed[0] = mask & 0x1;
+    m_firstRed[1] = (mask & 0x2) >> 1;
+    if(m_debayerTex)
+    {
+        f->glDeleteTextures(1, &m_debayerTex);
+        m_debayerTex = 0;
+    }
+    update();
+}
+
 void ImageWidget::setMTFParams(const MTFParam &params)
 {
     m_mtfParams = params;
@@ -684,6 +696,7 @@ void ImageWidget::debayer()
     f->glViewport(0, 0, m_imgWidth, m_imgHeight);
 
     m_debayerProgram->bind();
+    f->glUniform2i(m_debayerProgram->uniformLocation("firstRed"), m_firstRed[0], m_firstRed[1]);
     m_image->bind(0);
     f->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 
diff --git a/imagescrollareagl.h b/imagescrollareagl.h
index 07f56fa..e4a3bce 100644
--- a/imagescrollareagl.h
+++ b/imagescrollareagl.h
@@ -65,6 +65,7 @@ class ImageWidget : public QOpenGLWidget
     int m_thumbnailCount = 0;
     int m_maxTextureSize = 0;
     int m_maxArrayLayers = 0;
+    int m_firstRed[2] = {0, 0};
     QVector<ImageThumb> m_thumnails;
     Database *m_database = nullptr;
     QPointF m_lastPos;
@@ -79,6 +80,7 @@ public:
     void blockRepaint(bool block);
     void allocateThumbnails(const QStringList &paths);
     QVector2D getImagePixelCoord(const QVector2D &pos);
+    void setBayerMask(int mask);
 public slots:
     void setMTFParams(const MTFParam &params);
     void setOffset(float dx, float dy);
diff --git a/libXISF b/libXISF
index 8a1f305..aa35644 160000
--- a/libXISF
+++ b/libXISF
@@ -1 +1 @@
-Subproject commit 8a1f305cc71135003ef78c919787bbc2865f77af
+Subproject commit aa356443d308e848fcaa35d0470095f7a293aa76
diff --git a/mainwindow.cpp b/mainwindow.cpp
index 7c0f3e8..82bcd7c 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -173,6 +173,26 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
     viewMenu->addAction(tr("Zoom Out"), m_imageGL, SLOT(zoomOut()), QKeySequence::ZoomOut);
     viewMenu->addAction(tr("Best Fit"), m_imageGL, SLOT(bestFit()), QKeySequence("Ctrl+1"));
     viewMenu->addAction(tr("100%"), m_imageGL, SLOT(oneToOne()));
+    viewMenu->addSeparator();
+    QMenu *bayerMenu = viewMenu->addMenu(tr("Bayer mask"));
+    QActionGroup *bayerActionGroup = new QActionGroup(this);
+    QAction *rggbAction = bayerActionGroup->addAction(tr("RGGB"));//0 0
+    QAction *grbgAction = bayerActionGroup->addAction(tr("GRBG"));//1 0
+    QAction *gbrgAction = bayerActionGroup->addAction(tr("GBRG"));//0 1
+    QAction *bggrAction = bayerActionGroup->addAction(tr("BGGR"));//1 1
+    rggbAction->setCheckable(true); rggbAction->setData(0);
+    grbgAction->setCheckable(true); grbgAction->setData(1);
+    gbrgAction->setCheckable(true); gbrgAction->setData(2);
+    bggrAction->setCheckable(true); bggrAction->setData(3);
+    bayerMenu->addActions({rggbAction, grbgAction, gbrgAction, bggrAction});
+    viewMenu->addMenu(bayerMenu);
+    connect(bayerActionGroup, &QActionGroup::triggered, [this](QAction *action){
+        int data = action->data().toInt();
+        m_imageGL->imageWidget()->setBayerMask(data);
+        QSettings settings;
+        settings.setValue("mainwindow/bayermask", data);
+    });
+
     QAction *thumbnailsAction = viewMenu->addAction(tr("Thumbnails"), [this](bool checked){
         if(SettingsDialog::loadThumbsizes())m_ringList->clearThumbnails();
         m_imageGL->imageWidget()->allocateThumbnails(m_ringList->imageNames());
@@ -237,6 +257,19 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
     QSettings settings;
     restoreGeometry(settings.value("mainwindow/geometry").toByteArray());
     restoreState(settings.value("mainwindow/state").toByteArray());
+    int bayermask = settings.value("mainwindow/bayermask", 0).toInt();
+    switch(bayermask)
+    {
+    default:
+    case 0:
+        rggbAction->setChecked(true); break;
+    case 1:
+        grbgAction->setChecked(true); break;
+    case 2:
+        gbrgAction->setChecked(true); break;
+    case 3:
+        bggrAction->setChecked(true); break;
+    }
 
     QStringList standardLocations = QStandardPaths::standardLocations(QStandardPaths::PicturesLocation);
     if(standardLocations.size())
diff --git a/shaders/debayer.frag b/shaders/debayer.frag
index f31cc87..8830357 100644
--- a/shaders/debayer.frag
+++ b/shaders/debayer.frag
@@ -1,6 +1,7 @@
 #version 330
 
 uniform sampler2D qt_Texture0;
+uniform ivec2 firstRed;
 in vec2 qt_TexCoord0;
 in vec2 center;
 layout(location = 0) out vec4 color;
@@ -11,7 +12,7 @@ void main(void)
 {
     ivec2 texSize = textureSize(qt_Texture0, 0);
     ivec2 icenter = ivec2(center);
-    ivec2 alternate = icenter % 2;
+    ivec2 alternate = (icenter + firstRed) % 2;
 
     // cross, checker, theta, phi
     const vec4 kA = vec4(-1.0, -1.5,  0.5, -1.0) / 8.0;