From ab21f77b95f24c2f4470d9b8b4ed525ac14aee90 Mon Sep 17 00:00:00 2001
From: Lawrence Lee <45837045+Lawrence37@users.noreply.github.com>
Date: Mon, 1 Jan 2024 16:09:04 -0800
Subject: [PATCH] Implement Sony Pixel Shift for LibRaw

---
 rtengine/dcraw.h     | 10 +++++++
 rtengine/rawimage.cc | 66 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/rtengine/dcraw.h b/rtengine/dcraw.h
index 2bf8f2965..a6551b515 100644
--- a/rtengine/dcraw.h
+++ b/rtengine/dcraw.h
@@ -136,6 +136,15 @@ protected:
         ushort      *linebuf[_ltotal];
     };
 
+    /**
+     * Metadata for merged pixel-shift image.
+     */
+    struct MergedPixelshift
+    {
+        bool is_merged_pixelshift = false;
+        unsigned sub_frame_shot_select;
+    };
+
     int fuji_total_lines, fuji_total_blocks, fuji_block_width, fuji_bits, fuji_raw_type;
 
     ushort raw_height, raw_width, height, width, top_margin, left_margin;
@@ -162,6 +171,7 @@ protected:
     ThreeValBool RT_matrix_from_constant;
     std::string RT_software;
     double RT_baseline_exposure;
+    struct MergedPixelshift merged_pixelshift;
 
     struct PanasonicRW2Info {
         ushort bpp;
diff --git a/rtengine/rawimage.cc b/rtengine/rawimage.cc
index c7aca8b05..51ef67630 100644
--- a/rtengine/rawimage.cc
+++ b/rtengine/rawimage.cc
@@ -505,6 +505,22 @@ int RawImage::loadRaw(bool loadData, unsigned int imageNum, bool closeFile, Prog
         libraw->imgdata.rawparams.shot_select = shot_select;
 
         int err = libraw->open_buffer(ifp->data, ifp->size);
+
+        merged_pixelshift.is_merged_pixelshift =
+            err == LIBRAW_SUCCESS &&
+            (strncmp(libraw->unpack_function_name(), "sony_arq_load_raw", 17) == 0 &&
+                libraw->imgdata.idata.raw_count == 1 &&
+                libraw->imgdata.idata.colors == 4);
+
+        if (err == LIBRAW_REQUEST_FOR_NONEXISTENT_IMAGE || (merged_pixelshift.is_merged_pixelshift && shot_select)) {
+            // Try again last valid frame. Sony Pixel Shift, for example, has a
+            // single frame, but we want to represent the data as four.
+            shot_select = merged_pixelshift.is_merged_pixelshift ? shot_select / 4 : shot_select;
+            shot_select = std::min(shot_select, std::max(libraw->imgdata.idata.raw_count, 1u) - 1);
+            libraw->imgdata.rawparams.shot_select = shot_select;
+            err = libraw->open_buffer(ifp->data, ifp->size);
+        }
+
         if (err == LIBRAW_FILE_UNSUPPORTED || err == LIBRAW_TOO_BIG) {
             // fallback to the internal one
             return err;
@@ -532,6 +548,18 @@ int RawImage::loadRaw(bool loadData, unsigned int imageNum, bool closeFile, Prog
         colors = d.colors;
         tiff_bps = 0;
 
+        if (merged_pixelshift.is_merged_pixelshift ||
+            (strncmp(libraw->unpack_function_name(), "sony_arq_load_raw", 17) == 0 &&
+                is_raw == 1 && colors == 4)) {
+            // Represent merged pixelshift as 4 sub-frames.
+            merged_pixelshift.is_merged_pixelshift = true;
+            merged_pixelshift.sub_frame_shot_select = imageNum % 4;
+
+            filters = 0x94949494;
+            colors = 3;
+            is_raw = 4;
+        }
+
         for (int i = 0; i < 6; ++i) {
             for (int j = 0; j < 6; ++j) {
                 xtrans[i][j] = d.xtrans[i][j];
@@ -576,6 +604,9 @@ int RawImage::loadRaw(bool loadData, unsigned int imageNum, bool closeFile, Prog
             cam_mul[i] = cd.cam_mul[i];
             pre_mul[i] = cd.pre_mul[i];
         }
+        if (merged_pixelshift.is_merged_pixelshift) {
+            pre_mul[3] = 0.f; // 4th value is undefined after reducing to 3 colors.
+        }
 
         for (int i = 0; i < 3; ++i) {
             for (int j = 0; j < 4; ++j) {
@@ -1102,6 +1133,41 @@ float** RawImage::compress_image(unsigned int frameNum, bool freeImage)
 
         delete [] float_raw_image;
         float_raw_image = nullptr;
+    } else if (merged_pixelshift.is_merged_pixelshift) {
+        // Frame 0 is not shifted. Frame 1 is shifted down. Frame 2 is shifted
+        // down and right. Frame 3 is shifted right.
+        int h_shift = (merged_pixelshift.sub_frame_shot_select >> 1) & 1;
+        int v_shift = ((merged_pixelshift.sub_frame_shot_select + 1u) >> 1) & 1;
+
+        // Reset edges to 0.
+        for (int row = 0; row < v_shift; ++row) {
+            for (int col = 0; col < width; ++col) {
+                this->data[row][col] = 0;
+            }
+        }
+        for (int col = 0; col < h_shift; ++col) {
+            for (int row = 0; row < height; ++row) {
+                this->data[row][col] = 0;
+            }
+        }
+
+        const int image_v_shift = top_margin - v_shift;
+        const int image_h_shift = left_margin - h_shift;
+        const unsigned original_filters = filters;
+
+        filters = 0xb4b4b4b4; // R G1 B G2.
+
+#ifdef _OPENMP
+        #pragma omp parallel for
+#endif
+
+        for (int row = v_shift; row < height; row++) {
+            for (int col = h_shift; col < width; col++) {
+                this->data[row][col] = image[(row + image_v_shift) * iwidth + col + image_h_shift][FC(row, col)];
+            }
+        }
+
+        filters = original_filters;
     } else if (filters != 0 && !isXtrans()) {
 #ifdef _OPENMP
         #pragma omp parallel for