05、WindowsStoreapp的图片裁切

PhotoChooserTask photoChooserTask = new PhotoChooserTask();
photoChooserTask.Completed += new EventHandler(photoChooserTask_Completed);
// 设置 宽、高
photoChooserTask.PixelHeight = 130;
photoChooserTask.PixelWidth = 130;
photoChooserTask.ShowCamera = true;
photoChooserTask.Show();

<Image x:Name="img" Stretch="UniformToFill" ManipulationMode="All" ManipulationDelta="Image_ManipulationDelta" RenderTransformOrigin="0.5,0.5">
<Image.RenderTransform>
<CompositeTransform x:Name="img_transform" CenterX="0" CenterY="0"/>
Image.RenderTransform>
Image>
<Image x:Name="imgResult" Width="100" Height="100"/>

<Border IsHitTestVisible="False" x:Name="borderMask" BorderThickness="135,268.3" Background="Transparent" BorderBrush="#55000000" >
<Border BorderThickness="1" BorderBrush="White"/>
Border>

// 当页面布局发生改变时，动态调整遮罩的位置
this.SizeChanged += PhotoChooserPage_SizeChanged;

void PhotoChooserPage_SizeChanged(object sender, SizeChangedEventArgs e)
{
InitMask();
}
// 取景框的 宽、高，img 图片控件初始的最小宽、高要大于它
public double Img_w = 200;
// 取景框大小 - 作为标准
Rect measureRect;
void InitMask()
{
double w = Window.Current.Bounds.Width;
double h = Window.Current.Bounds.Height;

if (w > Img_w && h > Img_w)
{
// 左边距
double left = (w - Img_w) / 2;
// 上边距
double top = (h - Img_w) / 2;
// 取景框作为截图的标准
measureRect = new Rect(left, top, Img_w, Img_w);
// 把 Border 的边框设置为黑色半透明，背景为 null，则实现取景框效果
borderMask.BorderThickness = new Thickness(left, top, left, top);

borderMask.Width = w;
borderMask.Height = h;

Canvas.SetLeft(img, left);
Canvas.SetTop(img, top);
Canvas.SetLeft(imgResult, (w - imgResult.ActualWidth) / 2);
}
}

// 缩放累加
double scale = 1.0;
// 平移累加
double translate_x = 0;
double translate_y = 0;
object o = 1;
private void Image_ManipulationDelta(object sender, ManipulationDeltaRoutedEventArgs e)
{
e.Handled = true;
lock (o)
{
// 非惯性下
if (!e.IsInertial)
{
// x-y 屏幕坐标的更改
translate_x += e.Delta.Translation.X;
translate_y += e.Delta.Translation.Y;
// 两指缩放更改
scale *= e.Delta.Scale;
// 更改图片 CompositeTransform 对象
img_transform.TranslateX = translate_x;
img_transform.TranslateY = translate_y;
img_transform.ScaleX = img_transform.ScaleY = scale;
// 如果超出取景框，则撤销上面的修改
if (!IsValide())
{
translate_x -= e.Delta.Translation.X;
translate_y -= e.Delta.Translation.Y;
scale /= e.Delta.Scale;
img_transform.TranslateX = translate_x;
img_transform.TranslateY = translate_y;
img_transform.ScaleX = img_transform.ScaleY = scale;
}
}
}
}

// 判断图片在遮罩的中间位置
bool IsValide()
{
Rect Temp = GetBounds(img, LayoutRoot);
// 查找当前 Windows.Foundation.Rect 所表示的矩形和指定 Windows.Foundation.Rect 所表示的矩形的交集，并将结果存储为当前
// Windows.Foundation.Rect
Temp.Intersect(measureRect);
if (Temp == measureRect)
{
return true;
}
return false;
}
// 获取 UIElement 在页面中的坐标和尺寸
public Rect GetBounds(FrameworkElement childElement, FrameworkElement parentElement)
{
// https://msdn.microsoft.com/en-us/library/system.windows.media.visual.transformtovisual%28v=vs.110%29.aspx
// https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.uielement.transformtovisual.aspx
GeneralTransform transform = childElement.TransformToVisual(parentElement);
return transform.TransformBounds(new Rect(0, 0, childElement.ActualWidth, childElement.ActualHeight));
}

private async void AppBarButton_Crop_Click(object sender, RoutedEventArgs e)
{
appBar.IsEnabled = false;
try
{
StorageFile sourceFile = PickedFile;// await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFileAsync("Images\\test\\test.jpg");
if (PickedFile == null) return;
using (var readStream = await sourceFile.OpenReadAsync())
{
var decoder = await BitmapDecoder.CreateAsync(readStream);
//using (InMemoryRandomAccessStream writeStream = new InMemoryRandomAccessStream())
//{
if (WriteStream != null)
{
WriteStream.Dispose();
}
WriteStream = new InMemoryRandomAccessStream();
BitmapEncoder encoder = await BitmapEncoder.CreateForTranscodingAsync(WriteStream, decoder);
Rect temp = GetBounds(img, LayoutRoot);
double scale_x = decoder.PixelWidth / temp.Width;
encoder.BitmapTransform.Bounds = new BitmapBounds
{
X = (uint)Math.Round((measureRect.X - temp.X) * scale_x, 0),
Y = (uint)Math.Round((measureRect.Y - temp.Y) * scale_x, 0),
Width = (uint)Math.Round(measureRect.Width * scale_x, 0),
Height = (uint)Math.Round(measureRect.Height * scale_x, 0)
};
await encoder.FlushAsync();
BitmapImage bi = new BitmapImage();
bi.SetSource(WriteStream);
imgResult.Source = bi;
// 如果需要设置图片的固定宽、高，可以使用 WriteableBitmap 对象
//WriteableBitmap wb = new WriteableBitmap(120, 120);
//wb.SetSource(writeStream);
//imgResult.Source = wb;
double size = WriteStream.Size / (1024 * 1024.0);
if (size > 5)
await (new MessageDialog(string.Format("图片大于 5MB（当前{0:0.0}MB),请重新选择"))).ShowAsync();
//}
}
}
catch (Exception ex)
{
(new MessageDialog("截图区域超出边界了:" + ex.Message)).ShowAsync();
}
appBar.IsEnabled = true;
}