From 30d3edc9fd3b54a48e6d53dde81b31c3642cc216 Mon Sep 17 00:00:00 2001
From: Jorg Tretter <joe.tretter@kcc.com>
Date: Wed, 14 Jul 2021 10:35:08 -0500
Subject: [PATCH] Convert to 8-Bit Gray scale instead to save space.

---
 SShot/Program.cs | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/SShot/Program.cs b/SShot/Program.cs
index 6d8e9dc..1e2e13e 100644
--- a/SShot/Program.cs
+++ b/SShot/Program.cs
@@ -26,7 +26,7 @@ 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 = to8BitGS(captureBitmap);
                 captureBitmap.Save(filename, ImageFormat.Png);
             } catch (Exception ex) {
                 if (args.Length > 0) {
@@ -37,15 +37,36 @@ namespace SShot {
             }
         }
 
-        private static void toGrayscale(Bitmap bmp) {
+        private static Bitmap to8BitGS(Bitmap bmp) {
+            var result = new Bitmap(bmp.Width, bmp.Height, PixelFormat.Format8bppIndexed);
+
+            BitmapData data = result.LockBits(new Rectangle(0, 0, result.Width, result.Height), ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed);
+
+            // Copy the bytes from the image into a byte array
+            byte[] bytes = new byte[data.Width * data.Height ];
+            Marshal.Copy(data.Scan0, bytes, 0, bytes.Length);
+
             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;
+                    var rgb = (byte)((c.R + c.G + c.B) / 3);
 
-                    bmp.SetPixel (x,y,Color.FromArgb(c.A, rgb,rgb,rgb));
+                    bytes[y * data.Stride + x] = rgb;
                 }
             }
+
+            // Copy the bytes from the byte array into the image
+            Marshal.Copy(bytes, 0, data.Scan0, bytes.Length);
+
+            result.UnlockBits(data);
+
+            ColorPalette pal = result.Palette;
+            for (int i = 0; i < 256; i++) {
+                pal.Entries[i] = Color.FromArgb(255, i, i, i);
+            }
+            result.Palette = pal;
+
+            return result;
         }
     }
 }