How to load in a Bitmap from a canvas

Question

My problem is to load a Bitmap (for retrieving his pixels) from a canvas used to draw a image. So I need to have a Bitmap from a image drawn on a screen in a canvas.

This because Bitmap has the command GetPixel().

the canvas has no similar statement .

Thnx for any reply

Answer 1

Hi,@Paolo Mossa. Welcome to Microsoft Q&A.

To retrieve the pixels of an image drawn on a Canvas in WPF, you could follow following sample:

Use the Bitmap's GetPixel() method to retrieve the pixels.

 <StackPanel>

     <Canvas Background="LightGreen" Height="380">

         <Canvas x:Name="canvas" Background="AliceBlue" Width="300" Height="200">

         </Canvas>

     </Canvas>

     <Button Content="click" Click="Button_Click"/>

 </StackPanel>

Codebehind:

using System.Drawing;
using System.IO;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using Color = System.Drawing.Color;
using Size = System.Windows.Size;

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }
    int x = 100;
    int y = 50;

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        Size canvasSize = new Size(canvas.ActualWidth, canvas.ActualHeight);

       
        RenderTargetBitmap renderBitmap = new RenderTargetBitmap((int)canvasSize.Width, (int)canvasSize.Height, 96, 96, PixelFormats.Default);

        // Render the Canvas content onto the render target bitmap
        renderBitmap.Render(canvas);

        // Convert the render target bitmap to a Bitmap
        BitmapEncoder encoder = new PngBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
        using (MemoryStream ms = new MemoryStream())
        {
            encoder.Save(ms);
            Bitmap bitmap = new Bitmap(ms);
           
            if (x >= 0 && x < bitmap.Width && y >= 0 && y < bitmap.Height)
            {
            
                Color pixelColor = bitmap.GetPixel(x, y);

              
                MessageBox.Show($"Color at ({x}, {y}): R={pixelColor.R}, G={pixelColor.G}, B={pixelColor.B}");
               
            }
            else
            {
                MessageBox.Show("Coordinates are out of bounds.");
            }
            
        }
    }
}

The result:

Colot at(100,50):R=240,G=248,B=255

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