genesys: Add a way to configure shading pixel offset

backend/genesys/sensor.cpp

@@ -129,6 +129,7 @@ std::ostream& operator<<(std::ostream& out, const Genesys_Sensor& sensor)
         << "    register_dpiset: " << sensor.register_dpiset << '\n'
         << "    ccd_size_divisor: " << sensor.ccd_size_divisor << '\n'
         << "    shading_factor: " << sensor.shading_factor << '\n'
+        << "    shading_pixel_offset: " << sensor.shading_pixel_offset << '\n'
         << "    pixel_count_ratio: " << sensor.pixel_count_ratio << '\n'
         << "    output_pixel_offset: " << sensor.output_pixel_offset << '\n'
         << "    black_pixels: " << sensor.black_pixels << '\n'

backend/genesys/sensor.h

@@ -286,6 +286,9 @@ struct Genesys_Sensor {
     // How many real pixels correspond to one shading pixel that is sent to the scanner
     unsigned shading_factor = 1;
 
+    // How many pixels the shading data is offset from the acquired data
+    int shading_pixel_offset = 0;
+
     // This defines the ratio between logical pixel coordinates and the pixel coordinates sent to
     // the scanner.
     Ratio pixel_count_ratio = Ratio{1, 1};
@@ -365,6 +368,7 @@ struct Genesys_Sensor {
             shading_resolution == other.shading_resolution &&
             ccd_size_divisor == other.ccd_size_divisor &&
             shading_factor == other.shading_factor &&
+            shading_pixel_offset == other.shading_pixel_offset &&
             pixel_count_ratio == other.pixel_count_ratio &&
             output_pixel_offset == other.output_pixel_offset &&
             black_pixels == other.black_pixels &&
@@ -394,6 +398,7 @@ void serialize(Stream& str, Genesys_Sensor& x)
     serialize(str, x.shading_resolution);
     serialize(str, x.ccd_size_divisor);
     serialize(str, x.shading_factor);
+    serialize(str, x.shading_pixel_offset);
     serialize(str, x.output_pixel_offset);
     serialize(str, x.pixel_count_ratio);
     serialize(str, x.black_pixels);