[simple-scan] Improve quality of the Text scans.

[Bartosz <bkosiorek src gnome org>]

commit 647d3deaeb890e652c48cc7bb25db318b275c314
Author: Bartosz Kosiorek <gang65 poczta onet pl>
Date:   Sun Apr 12 23:28:17 2020 +0200

    Improve quality of the Text scans.
    
    Text scan (Gray) have less information to process, that't why is about 3 times
    faster than color mode. Unfortunately the quality of text scans are not good,
    as it is converted to 2 bit (black and white) images.
    To improve that conversion to black and white images was disabled.
    
    As a result the images have good quality, and the scanning process is fast.
    
    To scan images to black and white, the Lineart mode should be used.
    Unfortunately it is not supported by UX design.

 src/app-window.vala |  3 +--
 src/scanner.vala    | 54 -----------------------------------------------------
 2 files changed, 1 insertion(+), 56 deletions(-)
---
diff --git a/src/app-window.vala b/src/app-window.vala
index afb6ba7..e6c7470 100644
--- a/src/app-window.vala
+++ b/src/app-window.vala
@@ -967,14 +967,13 @@ public class AppWindow : Gtk.ApplicationWindow
         {
             options.scan_mode = ScanMode.GRAY;
             options.dpi = preferences_dialog.get_text_dpi ();
-            options.depth = 2;
         }
         else
         {
             options.scan_mode = ScanMode.COLOR;
             options.dpi = preferences_dialog.get_photo_dpi ();
-            options.depth = 8;
         }
+        options.depth = 8;
         preferences_dialog.get_paper_size (out options.paper_width, out options.paper_height);
         options.brightness = brightness;
         options.contrast = contrast;
diff --git a/src/scanner.vala b/src/scanner.vala
index c28e784..461fb5b 100644
--- a/src/scanner.vala
+++ b/src/scanner.vala
@@ -1326,10 +1326,6 @@ public class Scanner : Object
         info.width = parameters.pixels_per_line;
         info.height = parameters.lines;
         info.depth = parameters.depth;
-        /* Reduce bit depth if requested lower than received */
-        // FIXME: This a hack and only works on 8 bit gray to 2 bit gray
-        if (parameters.depth == 8 && parameters.format == Sane.Frame.GRAY && job.depth == 2 && job.scan_mode 
== ScanMode.GRAY)
-            info.depth = job.depth;
         info.n_channels = parameters.format == Sane.Frame.GRAY ? 1 : 3;
         info.dpi = job.dpi; // FIXME: This is the requested DPI, not the actual DPI
         info.device = current_device;
@@ -1469,56 +1465,6 @@ public class Scanner : Object
                 n_used++;
             }
 
-            /* Reduce bit depth if requested lower than received */
-            // FIXME: This a hack and only works on 8 bit gray to 2 bit gray
-            if (parameters.depth == 8 && parameters.format == Sane.Frame.GRAY &&
-                job.depth == 2 && job.scan_mode == ScanMode.GRAY)
-            {
-                uchar block = 0;
-                var write_offset = 0;
-                var block_shift = 6;
-                for (var i = 0; i < line.n_lines; i++)
-                {
-                    var offset = i * line.data_length;
-                    for (var x = 0; x < line.width; x++)
-                    {
-                         var p = line.data[offset + x];
-
-                         uchar sample;
-                         if (p >= 192)
-                             sample = 3;
-                         else if (p >= 128)
-                             sample = 2;
-                         else if (p >= 64)
-                             sample = 1;
-                         else
-                             sample = 0;
-
-                         block |= sample << block_shift;
-                         if (block_shift == 0)
-                         {
-                             line.data[write_offset] = block;
-                             write_offset++;
-                             block = 0;
-                             block_shift = 6;
-                         }
-                         else
-                             block_shift -= 2;
-                    }
-
-                    /* Finish each line on a byte boundary */
-                    if (block_shift != 6)
-                    {
-                        line.data[write_offset] = block;
-                        write_offset++;
-                        block = 0;
-                        block_shift = 6;
-                    }
-                }
-
-                line.data_length = (line.width * 2 + 7) / 8;
-            }
-
             notify_event (new NotifyGotLine (job.id, line));
         }
     }