How to: Convert an Image to Greyscale

This example shows how to convert an image to grayscale using FormatConvertedBitmap.

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

  <Page.Resources>

    <!-- This resource defines a BitmapImage with a source and a
         DecodePixelWidth of 200. This property is set to the same value 
         as the desired width of the image to save on memory use. This 
         BitmapImage is used as the base for the other BitmapSource resources. -->
    <BitmapImage x:Key="masterImage" DecodePixelWidth="200" 
     UriSource="C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Forest.jpg"/>

    <!-- This FormatConvertedBitmap uses the BitmapImage defined above and
         changes the format to Gray32Float (grayscale). -->
        <FormatConvertedBitmap x:Key="convertFormatImage" 
                               Source="{StaticResource masterImage}" 
                               DestinationFormat="Gray32Float" />

  </Page.Resources>

  <StackPanel>

    <!-- Apply the "convertFormatImage" resource defined above to this image.  -->
    <Image Width="200" Source="{StaticResource convertFormatImage}" />
  </StackPanel>
</Page>
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace SDKSample
{
    public partial class FormatConvertedBitmapExample : Page
    {
        public FormatConvertedBitmapExample()
        {

            ///// Create a BitmapImage and set it's DecodePixelWidth to 200. Use  ///// 
            ///// this BitmapImage as a source for other BitmapSource objects.    /////

            BitmapImage myBitmapImage = new BitmapImage();

            // BitmapSource objects like BitmapImage can only have their properties 
            // changed within a BeginInit/EndInit block.
            myBitmapImage.BeginInit();
            myBitmapImage.UriSource = new Uri(@"sampleImages/WaterLilies.jpg",UriKind.Relative);

            // To save significant application memory, set the DecodePixelWidth or   
            // DecodePixelHeight of the BitmapImage value of the image source to the desired  
            // height or width of the rendered image. If you don't do this, the application will  
            // cache the image as though it were rendered as its normal size rather then just  
            // the size that is displayed. 
            // Note: In order to preserve aspect ratio, set DecodePixelWidth 
            // or DecodePixelHeight but not both.
            myBitmapImage.DecodePixelWidth = 200;
            myBitmapImage.EndInit();

            ////////// Convert the BitmapSource to a new format //////////// 
            // Use the BitmapImage created above as the source for a new BitmapSource object 
            // which is set to a gray scale format using the FormatConvertedBitmap BitmapSource.                                                
            // Note: New BitmapSource does not cache. It is always pulled when required.

            FormatConvertedBitmap newFormatedBitmapSource = new FormatConvertedBitmap();

            // BitmapSource objects like FormatConvertedBitmap can only have their properties 
            // changed within a BeginInit/EndInit block.
            newFormatedBitmapSource.BeginInit();

            // Use the BitmapSource object defined above as the source for this new  
            // BitmapSource (chain the BitmapSource objects together).
            newFormatedBitmapSource.Source = myBitmapImage;

            // Set the new format to Gray32Float (grayscale).
            newFormatedBitmapSource.DestinationFormat = PixelFormats.Gray32Float;
            newFormatedBitmapSource.EndInit();

            // Create Image Element
            Image myImage = new Image();
            myImage.Width = 200;
            //set image source
            myImage.Source = newFormatedBitmapSource;

            // Add Image to the UI
            StackPanel myStackPanel = new StackPanel();
            myStackPanel.Children.Add(myImage);
            this.Content = myStackPanel;
        }
    }
}
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