genesys: Add a way to multiply the pixel counts sent to the scanner

backend/genesys_low.cc

@@ -1336,6 +1336,9 @@ void compute_session_pixel_offsets(const Genesys_Device* dev, ScanSession& s,
             s.pixel_endx = 0;
         }
     }
+
+    s.pixel_startx *= sensor.pixel_count_multiplier;
+    s.pixel_endx *= sensor.pixel_count_multiplier;
 }
 
 void compute_session(Genesys_Device* dev, ScanSession& s, const Genesys_Sensor& sensor)

backend/genesys_sensor.h

@@ -290,6 +290,9 @@ struct Genesys_Sensor {
     // CCD may present itself as half or quarter-size CCD on certain resolutions
     int ccd_size_divisor = 1;
 
+    // Some scanners need an additional multiplier over the scan coordinates
+    int pixel_count_multiplier = 1;
+
     int black_pixels = 0;
     // value of the dummy register
     int dummy_pixel = 0;