From 442df1882498263f800b1a1b01573b752147cb4e Mon Sep 17 00:00:00 2001
From: ghosttie <mrwizard@wizardstower.co.uk>
Date: Mon, 28 Mar 2022 17:22:56 -0400
Subject: [PATCH] fix negated 1bpp TIFs with Photometric.MINISBLACK

---
 Pdf/PdfDictionaryExtensions.cs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Pdf/PdfDictionaryExtensions.cs b/Pdf/PdfDictionaryExtensions.cs
index 23b203f..a8a40ec 100644
--- a/Pdf/PdfDictionaryExtensions.cs
+++ b/Pdf/PdfDictionaryExtensions.cs
@@ -175,6 +175,12 @@ private static Image ImageFromCCITTFaxDecode(PdfDictionary dictionary)
           for (int i = 0; i < imageData.Height; i++) {
             tiff.ReadScanline(buffer, i);
 
+            if (!ccittFaxDecodeParameters.BlackIs1) {
+              for (var j = 0; j < buffer.Length; j++) {
+                buffer[j] = (byte) (255 - buffer[j]);
+              }
+            }
+            
             Rectangle imgRect = new Rectangle(0, i, imageData.Width, 1);
             BitmapData imgData = bitmap.LockBits(imgRect, ImageLockMode.WriteOnly, PixelFormat.Format1bppIndexed);
             Marshal.Copy(buffer, 0, imgData.Scan0, buffer.Length);