我實現了一個行爲，這是最佳的，性能明智..我用它來從流媒體家庭安全攝像機活飼料，就像有相當大的圖像的魅力..
嘗試了這一點，讓我知道你怎麼看。用法非常簡單，分配依賴項屬性，將行爲附加到圖像並完成它。乾杯。
注意：像素可能是IList，但是您也可以分配一個數組，因爲C＃數組實現了IList。
注2：不要分配圖像源，因爲這會覆蓋行爲的分配，只能綁定到像素行爲的依賴屬性。
public class VideoBehavior : Behavior<Image>
{
public static readonly DependencyProperty PixelsProperty = DependencyProperty.Register(
"Pixels", typeof (IList<byte>), typeof (VideoBehavior), new PropertyMetadata(default(IList<byte>),OnPixelsChanged));
private static void OnPixelsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var b = (VideoBehavior) d;
var pixels = (IList<byte>) e.NewValue;
b.RenderPixels(pixels);
}
public IList<byte> Pixels
{
get { return (IList<byte>) GetValue(PixelsProperty); }
set { SetValue(PixelsProperty, value); }
}
public static readonly DependencyProperty PixelFormatProperty = DependencyProperty.Register(
"PixelFormat", typeof (PixelFormat), typeof (VideoBehavior), new PropertyMetadata(PixelFormats.Default,OnPixelFormatChanged));
private static void OnPixelFormatChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var b = (VideoBehavior) d;
var pixelFormat = (PixelFormat) e.NewValue;
if(pixelFormat==PixelFormats.Default)
return;
b._pixelFormat = pixelFormat;
b.InitializeBufferIfAttached();
}
public PixelFormat PixelFormat
{
get { return (PixelFormat) GetValue(PixelFormatProperty); }
set { SetValue(PixelFormatProperty, value); }
}
public static readonly DependencyProperty PixelWidthProperty = DependencyProperty.Register(
"PixelWidth", typeof (int), typeof (VideoBehavior), new PropertyMetadata(default(int),OnPixelWidthChanged));
private static void OnPixelWidthChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var b = (VideoBehavior)d;
var value = (int)e.NewValue;
if(value<=0)
return;
b._pixelWidth = value;
b.InitializeBufferIfAttached();
}
public int PixelWidth
{
get { return (int) GetValue(PixelWidthProperty); }
set { SetValue(PixelWidthProperty, value); }
}
public static readonly DependencyProperty PixelHeightProperty = DependencyProperty.Register(
"PixelHeight", typeof (int), typeof (VideoBehavior), new PropertyMetadata(default(int),OnPixelHeightChanged));
private static void OnPixelHeightChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var b = (VideoBehavior)d;
var value = (int)e.NewValue;
if (value <= 0)
return;
b._pixelHeight = value;
b.InitializeBufferIfAttached();
}
public int PixelHeight
{
get { return (int) GetValue(PixelHeightProperty); }
set { SetValue(PixelHeightProperty, value); }
}
public static readonly DependencyProperty DpiXProperty = DependencyProperty.Register(
"DpiX", typeof (int), typeof (VideoBehavior), new PropertyMetadata(96,OnDpiXChanged));
private static void OnDpiXChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var b = (VideoBehavior)d;
var value = (int)e.NewValue;
if (value <= 0)
return;
b._dpiX = value;
b.InitializeBufferIfAttached();
}
public int DpiX
{
get { return (int) GetValue(DpiXProperty); }
set { SetValue(DpiXProperty, value); }
}
public static readonly DependencyProperty DpiYProperty = DependencyProperty.Register(
"DpiY", typeof (int), typeof (VideoBehavior), new PropertyMetadata(96,OnDpiYChanged));
private static void OnDpiYChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var b = (VideoBehavior)d;
var value = (int)e.NewValue;
if (value <= 0)
return;
b._dpiY = value;
b.InitializeBufferIfAttached();
}
public int DpiY
{
get { return (int) GetValue(DpiYProperty); }
set { SetValue(DpiYProperty, value); }
}
[DllImport("kernel32.dll", EntryPoint = "RtlMoveMemory")]
public static extern void CopyMemory(IntPtr destination, IntPtr source, uint length);
private IntPtr _backBuffer = IntPtr.Zero;
private int _bytesPerPixel;
private const int BitsPerByte = 8;
private int _pixelWidth;
private int _pixelHeight;
private int _dpiX;
private int _dpiY;
private PixelFormat _pixelFormat;
private Int32Rect _rect;
private uint _byteArraySize;
private WriteableBitmap _bitMap;
private bool _attached;
protected override void OnAttached()
{
_attached = true;
InitializeBufferIfAttached();
}
private void InitializeBufferIfAttached()
{
if(_attached==false)
return;
ReevaluateBitsPerPixel();
RecomputeByteArraySize();
ReinitializeImageSource();
}
private void ReevaluateBitsPerPixel()
{
if(_pixelFormat==PixelFormats.Default)
return;
_bytesPerPixel = _pixelFormat.BitsPerPixel/BitsPerByte;
}
private void ReinitializeImageSource()
{
if(_pixelHeight<=0|| _pixelHeight<=0)
return;
_bitMap = new WriteableBitmap(_pixelWidth, _pixelHeight, _dpiX, _dpiY, _pixelFormat, null);
_backBuffer = _bitMap.BackBuffer;
_rect = new Int32Rect(0, 0, _pixelWidth, _pixelHeight);
AssociatedObject.Source = _bitMap;
}
private async void RenderPixels(IList<byte> pixels)
{
if (_backBuffer == IntPtr.Zero)
return;
if (pixels == null)
{
return;
}
await Task.Factory.StartNew(() =>
{
var h = new GCHandle();
var allocated = false;
try
{
h = GCHandle.Alloc(pixels, GCHandleType.Pinned);
allocated = true;
var ptr = h.AddrOfPinnedObject();
CopyMemory(_backBuffer, ptr, _byteArraySize);
}
finally
{
if (allocated)
h.Free();
}
});
_bitMap.Lock();
_bitMap.AddDirtyRect(_rect);
_bitMap.Unlock();
}
private void RecomputeByteArraySize()
{
_byteArraySize = (uint)(_pixelWidth * _pixelHeight * _bytesPerPixel);
}
}
好的問題 - 有沒有人有任何線索爲什麼BitmapImage的行爲是這樣的？ –
RenderOptions.BitmapScalingMode屬性（應用於實際顯示圖像的任何控件，通常是XAML元素）可以提供幫助嗎？我認爲默認情況下，它被設置爲.NET 3.5中的HighQuality和.NET 4中的LowQuality，但兩者在渲染速度上都會受到不同程度的損失... –
Marko
我正在研究一個大量（數千個）的圖像 - 無論是JPG或BMP，我試圖優化速度更快的播放速度。一方面，位圖更大，需要更長時間從磁盤或內存緩存中加載，但它們不需要解碼。使用jpgs，情況正好相反 - 解碼速度很慢，但從磁盤加載很快。最後，我最終選擇了圖像的原始格式（jpg），因爲這需要較少的初始處理。重點是緩存和磁盤加載可能會影響時間。 – Dean