前端
<Canvas x:Name="imageCanvas" Background="Transparent"MouseLeftButtonDown="ImageCanvas_MouseLeftButtonDown"MouseMove="ImageCanvas_MouseMove"MouseLeftButtonUp="ImageCanvas_MouseLeftButtonUp"MouseWheel="ImageCanvas_MouseWheel"ClipToBounds="True"><Image x:Name="imgAnswer" Stretch="Uniform" Source="{Binding Answer.ImgContent}" Visibility="{Binding Answer.ImgContentVisibility}"><Image.RenderTransform><MatrixTransform x:Name="imageTransform"/></Image.RenderTransform></Image>
</Canvas>
后台逻辑
// 状态变量private Point _lastMousePosition;private bool _isDragging = false;private Matrix _matrix = Matrix.Identity;// 触摸状态private Point? _lastTouchPoint1 = null;private Point? _lastTouchPoint2 = null;// 缩放限制private const double MIN_SCALE = 0.1;private const double MAX_SCALE = 10.0;private void ImageCanvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e){if (imgAnswer.Visibility != Visibility.Visible || imgAnswer.Source == null)return;_isDragging = true;_lastMousePosition = e.GetPosition(imageCanvas);imageCanvas.CaptureMouse();imgAnswer.Cursor = Cursors.Hand;e.Handled = true;}private void ImageCanvas_MouseMove(object sender, MouseEventArgs e){if (!_isDragging || e.LeftButton != MouseButtonState.Pressed)return;if (imgAnswer.Visibility != Visibility.Visible || imgAnswer.Source == null)return;try{Point currentPosition = e.GetPosition(imageCanvas);double deltaX = currentPosition.X - _lastMousePosition.X;double deltaY = currentPosition.Y - _lastMousePosition.Y;_matrix.OffsetX += deltaX;_matrix.OffsetY += deltaY;imageTransform.Matrix = _matrix;_lastMousePosition = currentPosition;e.Handled = true;}catch{// 忽略错误}}private double _currentScale = 1.0; // 当前缩放比例private void ImageCanvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e){_isDragging = false;imageCanvas.ReleaseMouseCapture();imgAnswer.Cursor = Cursors.Arrow;e.Handled = true;}private void ImageCanvas_MouseWheel(object sender, MouseWheelEventArgs e){// 计算缩放因子（滚轮向上放大，向下缩小）double scaleFactor = e.Delta > 0 ? 1.1 : 0.9;_currentScale *= scaleFactor;// 获取鼠标当前位置（作为缩放中心）Point center = e.GetPosition(imageCanvas);// 应用缩放变换到所有笔迹ApplyScaleToAllStrokes(scaleFactor, center);e.Handled = true;}// 应用缩放private void ApplyScaleToAllStrokes(double scaleFactor, Point center){// 创建缩放矩阵（以 center 为中心）_matrix.Translate(-center.X, -center.Y); // 平移到原点_matrix.Scale(scaleFactor, scaleFactor); // 缩放_matrix.Translate(center.X, center.Y); // 平移回原中心// 应用变换到笔迹imageTransform.Matrix = _matrix;}
