Add gray scale conversion

SShot/Program.cs

@@ -5,6 +5,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using System.Windows.Forms;
+using System.Runtime.InteropServices;
 
 namespace SShot {
     static class Program {
@@ -25,16 +26,26 @@ namespace SShot {
                 Bitmap captureBitmap = new Bitmap(captureRectangle.Width, captureRectangle.Height, PixelFormat.Format32bppArgb);
                 Graphics captureGraphics = Graphics.FromImage(captureBitmap);
                 captureGraphics.CopyFromScreen(captureRectangle.Left, captureRectangle.Top, 0, 0, captureRectangle.Size);
+                toGrayscale(captureBitmap);
                 captureBitmap.Save(filename, ImageFormat.Png);
-            }
-            catch (Exception ex) {
+            } catch (Exception ex) {
                 if (args.Length > 0) {
-                    if (args[0] != "-QuietErrors")  {
+                    if (args[0] != "-QuietErrors") {
                         MessageBox.Show(ex.Message);
                     }
                 }
             }
         }
 
+        private static void toGrayscale(Bitmap bmp) {
+            for (int y = 0; y < bmp.Height; y++) {
+                for (int x = 0; x < bmp.Width; x++) {
+                    var c = bmp.GetPixel(x, y);
+                    int rgb = (c.R + c.G + c.B) / 3;
+
+                    bmp.SetPixel (x,y,Color.FromArgb(c.A, rgb,rgb,rgb));
+                }
+            }
+        }
     }
 }