Merge pull request #627 from telerik/new-kb-convert-pdf-grayscale-aspnet-core-fd3e385adb22424586ed21d0f1a23422

Added new kb article convert-pdf-grayscale-aspnet-core

Author: YoanKar

knowledge-base/convert-color-pdf-to-black-and-white-telerik-document-processing.md

@@ -202,3 +202,4 @@ Ensure to adjust the `MakeGrayscale` methods for `ColorBase`, `Path`, and `Image
 - [RadPdfProcessing Overview]({%slug radpdfprocessing-overview%})
 - [How to Generate a PDF Document from Images with FixedContentEditor]({%slug pdf-from-images-with-fixedcontenteditor%}) 
 - [How to Generate a PDF Document from Images with RadFixedDocumentEditor]({%slug pdf-from-images-with-radfixeddocumenteditor%})
+- [Converting Colored PDF Document Images to GrayScale in .NET Standard]({%slug convert-pdf-grayscale-aspnet-core%})

knowledge-base/convert-pdf-grayscale-aspnet-core.md

@@ -0,0 +1,135 @@
+---
+title: Converting Colored PDF Document Images to GrayScale in .NET Standard
+description: Learn how to convert colored images in PDF documents to grayscale using Telerik PdfProcessing in an ASP.NET Core (.NET 9) environment.
+type: how-to
+page_title: How to Convert Colored PDF Document Images to GrayScale in .NET Standard
+meta_title: How to Convert Colored PDF Document Images to GrayScale in .NET Standard
+slug: convert-pdf-grayscale-aspnet-core
+tags: pdf, processing, telerik, document, asp, core, convert, grayscale, image, gray, black, white, color
+res_type: kb
+ticketid: 1697916
+---
+
+## Environment
+
+| Version | Product | Author | 
+| ---- | ---- | ---- | 
+| 2025.3.806| RadPdfProcessing |[Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova)| 
+
+## Description
+
+Convert colored images in PDF documents using Telerik [PdfProcessing]({%slug radpdfprocessing-overview%}) in an ASP.NET Core (.NET 9) environment. 
+
+![Converting Colored PDF Documents to GrayScale](images/colored-to-grayscale.gif)   
+
+
+## Solution
+
+To convert colored PDFs to grayscale in ASP.NET Core (.NET 9), follow these steps:
+
+1. Use the Telerik [PdfProcessing]({%slug radpdfprocessing-overview%}) library to load and manipulate PDF content.
+2. Replace the image processing logic with a custom implementation using `System.Drawing`.
+
+Here is the complete code example:
+
+```csharp
+using System;
+using System.Diagnostics;
+using System.Drawing;
+using System.IO;
+using Telerik.Windows.Documents.Fixed.FormatProviders.Pdf;
+using Telerik.Windows.Documents.Fixed.Model;
+using Telerik.Windows.Documents.Fixed.Model.Objects;
+using Telerik.Windows.Documents.ImageUtils;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        // Initialize ImagePropertiesResolver
+        ImagePropertiesResolver defaultImagePropertiesResolver = new ImagePropertiesResolver();
+        Telerik.Windows.Documents.Extensibility.FixedExtensibilityManager.ImagePropertiesResolver = defaultImagePropertiesResolver;
+
+        string inputPath = "colored.pdf"; // Path to the input PDF
+        string outputPath = "grayscale.pdf"; // Path for the grayscale output
+
+        ConvertPdfToGrayscale(inputPath, outputPath); 
+
+        Process.Start(new ProcessStartInfo() { FileName = outputPath, UseShellExecute = true });
+    }
+
+    /// <summary>
+    /// Converts all content in a PDF document to grayscale.
+    /// </summary>
+    public static void ConvertPdfToGrayscale(string inputPath, string outputPath)
+    {
+        PdfFormatProvider provider = new PdfFormatProvider();
+        RadFixedDocument document = provider.Import(File.ReadAllBytes(inputPath), TimeSpan.FromSeconds(10));
+
+        foreach (RadFixedPage page in document.Pages)
+        {
+            foreach (ContentElementBase element in page.Content)
+            {
+                Image img = element as Image;
+                if (img != null)
+                {
+                    ImageSource source = img.ImageSource;
+                    EncodedImageData encodedImageData = source.GetEncodedImageData();
+                    byte[] original = encodedImageData.Data;
+
+                    Bitmap grayBitmap = ConvertToGrayscale(original);
+
+                    // Save the grayscale bitmap to a temporary file
+                    string tempImagePath = "temp_grayscale_image.jpeg";
+                    grayBitmap.Save(tempImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);
+                    
+                    // Update the image source in the PDF
+                    using (FileStream fs = File.Open(tempImagePath, FileMode.Open))
+                    {
+                        ImageSource grayscaleImageSource = new ImageSource(fs);
+                        img.ImageSource = grayscaleImageSource;
+                    }
+                }
+            }
+        }
+
+        // Save the modified PDF to the output path
+        if (File.Exists(outputPath))
+        {
+            File.Delete(outputPath);
+        }
+
+        File.WriteAllBytes(outputPath, provider.Export(document, TimeSpan.FromSeconds(10)));
+    }
+
+    /// <summary>
+    /// Converts a byte array of image data to grayscale.
+    /// </summary>
+    public static Bitmap ConvertToGrayscale(byte[] imageBytes)
+    {
+        using (var ms = new MemoryStream(imageBytes))
+        {
+            using (var originalImage = new Bitmap(ms))
+            {
+                Bitmap grayBitmap = new Bitmap(originalImage.Width, originalImage.Height);
+
+                for (int y = 0; y < originalImage.Height; y++)
+                {
+                    for (int x = 0; x < originalImage.Width; x++)
+                    {
+                        Color originalColor = originalImage.GetPixel(x, y);
+                        int grayValue = (int)(originalColor.R * 0.3 + originalColor.G * 0.59 + originalColor.B * 0.11);
+                        Color grayColor = Color.FromArgb(grayValue, grayValue, grayValue);
+                        grayBitmap.SetPixel(x, y, grayColor);
+                    }
+                }
+                return grayBitmap;
+            }
+        }
+    }
+}
+```
+
+## See Also
+
+- [Converting Colored PDF Documents to GrayScale in .NET Framework]({%slug convert-color-pdf-to-black-and-white-telerik-document-processing%})