How to crop image and save into ImageSource in WPF? - wpf

Question

I am new learner to WPF. here I got a question.
I have a image, width:360, height:360. Here I want to crop this image like below:
( 0,0 ) to (120,120) save to the first ImageSource object,
(120,0 ) to (240,120) save to the second ImageSource object,
(240,0 ) to (360,120) save to the third ImageSource object;,
……
pls see more details in below picture:
My code sample 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, seems that all the ImageSource objects store the same image, not the corping part. Any one can 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);
}