genesys: Simplify physical pixel count computation on gl846

backend/genesys/low.cpp

@@ -885,9 +885,7 @@ void compute_session_pixel_offsets(const Genesys_Device* dev, ScanSession& s,
         s.pixel_startx += sensor.ccd_start_xoffset * ccd_pixels_per_system_pixel;
         s.pixel_endx = s.pixel_startx + s.optical_pixels_raw;
 
-        if (dev->model->asic_type == AsicType::GL845 ||
-            dev->model->asic_type == AsicType::GL846)
-        {
+        if (dev->model->asic_type == AsicType::GL845) {
             s.pixel_startx /= s.hwdpi_divisor * s.segment_count * ccd_pixels_per_system_pixel;
             s.pixel_endx /= s.hwdpi_divisor * s.segment_count * ccd_pixels_per_system_pixel;
         }

backend/genesys/tables_sensor.cpp

@@ -2717,7 +2717,25 @@ void genesys_init_sensor_tables()
     sensor.get_register_hwdpi_fun = default_get_register_hwdpi;
     sensor.get_hwdpi_divisor_fun = default_get_hwdpi_divisor_for_dpi;
     sensor.get_ccd_size_divisor_fun = default_get_ccd_size_divisor_for_dpi;
-    s_sensors->push_back(sensor);
+    {
+        struct CustomSensorSettings
+        {
+            ValueFilterAny<unsigned> resolutions;
+            Ratio pixel_count_ratio;
+        };
+
+        CustomSensorSettings custom_settings[] = {
+            { { 75, 100, 150, 300, 600 }, Ratio{1, 4} },
+            { { 1200 }, Ratio{1, 2} },
+        };
+
+        for (const CustomSensorSettings& setting : custom_settings) {
+            sensor.resolutions = setting.resolutions;
+            sensor.pixel_count_ratio = setting.pixel_count_ratio;
+            s_sensors->push_back(sensor);
+        }
+    }
+
 
     sensor = Genesys_Sensor();
     sensor.sensor_id = SensorId::CCD_PLUSTEK_OPTICBOOK_3800;