genesys: Remove true_gray variable by deriving its value directly

backend/genesys/genesys.cpp

@@ -4370,12 +4370,6 @@ static Genesys_Settings calculate_scan_settings(Genesys_Scanner* s)
         settings.color_filter = ColorFilter::NONE;
     }
 
-    if (s->color_filter == "None") {
-        settings.true_gray = 1;
-    } else {
-        settings.true_gray = 0;
-    }
-
     // brightness and contrast only for for 8 bit scans
     if (s->bit_depth == 8) {
         settings.contrast = (s->contrast * 127) / 100;

backend/genesys/gl646.cpp

@@ -606,7 +606,9 @@ void CommandSetGl646::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     }
 
   /* true CIS gray if needed */
-    if (dev->model->is_cis && session.params.channels == 1 && dev->settings.true_gray) {
+    if (dev->model->is_cis && session.params.channels == 1 &&
+        session.params.color_filter == ColorFilter::NONE)
+    {
         regs->find_reg(0x05).value |= REG_0x05_LEDADD;
     } else {
         regs->find_reg(0x05).value &= ~REG_0x05_LEDADD;

backend/genesys/gl841.cpp

@@ -1093,7 +1093,8 @@ ScanSession CommandSetGl841::calculate_scan_session(const Genesys_Device* dev,
     ScanFlag flags = ScanFlag::NONE;
 
     // true gray (led add for cis scanners)
-    if (dev->model->is_cis && dev->settings.true_gray &&
+    if (dev->model->is_cis &&
+        settings.color_filter == ColorFilter::NONE &&
         dev->settings.scan_mode != ScanColorMode::COLOR_SINGLE_PASS &&
         dev->model->sensor_id != SensorId::CIS_CANON_LIDE_80)
     {

backend/genesys/low.cpp

@@ -1119,7 +1119,8 @@ void compute_session(const Genesys_Device* dev, ScanSession& s, const Genesys_Se
         dev->model->asic_type == AsicType::GL845 ||
         dev->model->asic_type == AsicType::GL846)
     {
-        s.enable_ledadd = (s.params.channels == 1 && dev->model->is_cis && dev->settings.true_gray);
+        s.enable_ledadd = (s.params.channels == 1 && dev->model->is_cis &&
+                           s.params.color_filter == ColorFilter::NONE);
     }
 
     s.use_host_side_calib = sensor.use_host_side_calib;

backend/genesys/settings.h

@@ -76,9 +76,6 @@ struct Genesys_Settings
 
     ColorFilter color_filter = ColorFilter::NONE;
 
-    // true if scan is true gray, false if monochrome scan
-    int true_gray = 0;
-
     // value for contrast enhancement in the [-100..100] range
     int contrast = 0;