wpf-images

Image is a base abstract class representing images in GDI+. Bitmap is a concrete implementation of this base class.

BitmapImage is a way to represent an image in a vector based GUI engine like WPF and Silverlight. Contrary to a Bitmap, it is not based on GDI+. It is based on the Windows Imaging Component.

msdn

<!-- Simple image rendering. However, rendering an image this way may not
     result in the best use of application memory. See markup below which
     creates the same end result but using less memory. -->
<Image Width="200" 
Source="C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water Lilies.jpg"/>

<Image Width="200">
  <Image.Source>
    <!-- To save significant application memory, set the DecodePixelWidth or  
     DecodePixelHeight of the BitmapImage value of the image source to the desired 
     height and 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, only set either DecodePixelWidth
         or DecodePixelHeight but not both. -->
    <BitmapImage DecodePixelWidth="200"  
     UriSource="C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water Lilies.jpg" />
  </Image.Source>
</Image>

使用图片资源

<Window x:Class="fwPlcCheckAssist.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
       ...
        Title="fwPlcCheckAssist-2021.03.16 1023" Height="800" Width="1000">
    <Window.Resources>
        <BitmapImage x:Key="img_black"  UriSource="img/black-48.png" DecodePixelWidth="48" />
        <BitmapImage x:Key="img_green" UriSource="img/green-48.png" DecodePixelWidth="48" />
        <BitmapImage x:Key="img_red" UriSource="img/red-48.png" DecodePixelWidth="24" />
        <BitmapImage x:Key="img_black24"  UriSource="img/black-48.png" DecodePixelWidth="24" />
    </Window.Resources>
    <Grid>
    ...
    </Grid>

img_next.Source = FindResource("img_red") as BitmapImage;