How to crop an image and save to ImageSource in WPF?

Question

I am a new student of WPF. here i have a question. I have an image, width: 360, height: 360. Here I want to crop this image, as shown below:

(0,0) - (120,120) save to the first ImageSource object,

(120,0) - (240,120) save to the second ImageSource object,

(240,0) - (360,120) save to the third ImageSource object;

......

Pls see more details in the picture below:

My sample code is below:

private void CutImage(string img) { int iLeft = 0; int iTop = 0; int count = 0; Image thisImg = new Image(); BitmapImage src = new BitmapImage(); src.BeginInit(); src.UriSource = new Uri(img, UriKind.Relative); src.CacheOption = BitmapCacheOption.OnLoad; src.EndInit(); thisImg.Source = src; for (int i = 0; i < 3; i++) { iTop = i * 120; for (int j = 0; j < 3; j++) { iLeft = j * 120; Canvas canvas = new Canvas(); Rectangle destRect = new Rectangle(); destRect.SetValue(Canvas.LeftProperty, (double)0); destRect.SetValue(Canvas.TopProperty,(double)0); destRect.Width = destRect.Height = 120; Rect srcRect = new Rect(); srcRect.X = iLeft; srcRect.Y = iTop; srcRect.Width = srcRect.Height = 120; thisImg.Clip = new RectangleGeometry(srcRect); thisImg.Clip.SetValue(Canvas.TopProperty, (double)iTop); thisImg.Clip.SetValue(Canvas.LeftProperty, (double)iLeft); thisImg.Clip.SetValue(Canvas.WidthProperty, (double)120); thisImg.Clip.SetValue(Canvas.HeightProperty,(double)120); objImg[count++] = (ImageSource)thisImg.GetValue(Image.SourceProperty); } } } 

but it doesn’t work as I expected, it seems that all ImageSource objects keep the same image, and not part of the body. Can anybody help me? THX

Answer 1

Use CroppedBitmap to do this:

 private void CutImage(string img) { int count = 0; BitmapImage src = new BitmapImage(); src.BeginInit(); src.UriSource = new Uri(img, UriKind.Relative); src.CacheOption = BitmapCacheOption.OnLoad; src.EndInit(); for (int i = 0; i < 3; i++) for (int j = 0; j < 3; j++) objImg[count++] = new CroppedBitmap(src, new Int32Rect(j * 120, i * 120, 120, 120)); } 

Answer 2

Just do:

 private static BitmapSource CaptureScreen(Visual target, double dpiX, double dpiY) { if (target == null) { return null; } Rect bounds = VisualTreeHelper.GetDescendantBounds(target); RenderTargetBitmap rtb = new RenderTargetBitmap((int)(bounds.Width * dpiX / 96.0), (int)(bounds.Height * dpiY / 96.0), dpiX, dpiY, PixelFormats.Pbgra32); DrawingVisual dv = new DrawingVisual(); using (DrawingContext ctx = dv.RenderOpen()) { VisualBrush vb = new VisualBrush(target); ctx.DrawRectangle(vb, null, new Rect(new Point(), bounds.Size)); } rtb.Render(dv); return rtb; } VisualBrush part1 = new VisualBrush(yourVISUAL); part1.ViewBoxUnits = ..Absolute; part1.ViewBox = new Rect(x, y, width, height); BitmapSource bitmapSource = CaptureScreen(part1, 96, 96); using (var fileStream = new FileStream(filePath, FileMode.Create)) { BitmapEncoder encoder = new PngBitmapEncoder(); encoder.Frames.Add(BitmapFrame.Create(bitmapSource)); encoder.Save(fileStream); }