我该如何在WPF中进行像素级渲染(比如用于光线追踪)?我的初步想法是创建一个BitmapImage,修改缓冲区并在Image控件中显示它,但我不知道如何创建它(create方法需要一块非托管内存)。
我强烈反对前两个建议。WriteableBitmap类提供了您需要的功能,假设您正在使用3.5 SP1。在SP1之前,在WPF中没有真正好的答案,除非您采用一些严重的诡计。
如果您正在考虑进行类似光线追踪器的工作,需要绘制大量点,则可能希望直接在位图的内存空间中绘制,而不是通过抽象层绘制。这段代码将为您提供显着更好的渲染时间,但代价是需要使用“不安全”的代码,这可能或可能不是您的选择。
unsafe
{
System.Drawing.Point point = new System.Drawing.Point(320, 240);
IntPtr hBmp;
Bitmap bmp = new Bitmap(640, 480);
Rectangle lockRegion = new Rectangle(0, 0, 640, 480);
BitmapData data = bmp.LockBits(lockRegion, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
byte* p;
p = (byte*)data.Scan0 + (point.Y * data.Stride) + (point.X * 3);
p[0] = 0; //B pixel
p[1] = 255; //G pixel
p[2] = 255; //R pixel
bmp.UnlockBits(data);
//Convert the bitmap to BitmapSource for use with WPF controls
hBmp = bmp.GetHbitmap();
Canvas.Source = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(hbmpCanvas, IntPtr.Zero, Int32Rect.Empty, System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
Canvas.Source.Freeze();
DeleteObject(hBmp); //Clean up original bitmap
}
如果您要清理 hBitmap,您需要在类文件的顶部声明以下内容:
[System.Runtime.InteropServices.DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);
还要注意,您需要设置项目属性以允许不安全的代码。您可以通过在解决方案资源管理器中右键单击项目并选择属性来执行此操作。 转到生成选项卡。 选中“允许不安全的代码”框。 我也认为您需要添加对System.Drawing的引用。
如果需要,您可以添加小矩形,但每个小矩形都是 FrameworkElement ,所以这可能会有点重。另一个选项是创建一个 DrawingVisual,绘制它,渲染它,然后将其放入图像中:
private void DrawRubbish()
{
DrawingVisual dv = new DrawingVisual();
using (DrawingContext dc = dv.RenderOpen())
{
Random rand = new Random();
for (int i = 0; i < 200; i++)
dc.DrawRectangle(Brushes.Red, null, new Rect(rand.NextDouble() * 200, rand.NextDouble() * 200, 1, 1));
dc.Close();
}
RenderTargetBitmap rtb = new RenderTargetBitmap(200, 200, 96, 96, PixelFormats.Pbgra32);
rtb.Render(dv);
Image img = new Image();
img.Source = rtb;
MainGrid.Children.Add(img);
}
private void AddPixel(double x, double y)
{
Rectangle rec = new Rectangle();
Canvas.SetTop(rec, y);
Canvas.SetLeft(rec, x);
rec.Width = 1;
rec.Height = 1;
rec.Fill = new SolidColorBrush(Colors.Red);
myCanvas.Children.Add(rec);
}
public void DrawRectangle(WriteableBitmap writeableBitmap, int left, int top, int width, int height, Color color)
{
// Compute the pixel's color
int colorData = color.R << 16; // R
colorData |= color.G << 8; // G
colorData |= color.B << 0; // B
int bpp = writeableBitmap.Format.BitsPerPixel / 8;
unsafe
{
for (int y = 0; y < height; y++)
{
// Get a pointer to the back buffer
int pBackBuffer = (int)writeableBitmap.BackBuffer;
// Find the address of the pixel to draw
pBackBuffer += (top + y) * writeableBitmap.BackBufferStride;
pBackBuffer += left * bpp;
for (int x = 0; x < width; x++)
{
// Assign the color data to the pixel
*((int*)pBackBuffer) = colorData;
// Increment the address of the pixel to draw
pBackBuffer += bpp;
}
}
}
writeableBitmap.AddDirtyRect(new Int32Rect(left, top, width, height));
}
使用这个功能:
private WriteableBitmap bitmap = new WriteableBitmap(1100, 1100, 96d, 96d, PixelFormats.Bgr24, null);
private void Button_Click(object sender, RoutedEventArgs e)
{
int size = 10;
Random rnd = new Random(DateTime.Now.Millisecond);
bitmap.Lock(); // Lock() and Unlock() could be moved to the DrawRectangle() method. Just do some performance tests.
for (int y = 0; y < 99; y++)
{
for (int x = 0; x < 99; x++)
{
byte colR = (byte)rnd.Next(256);
byte colG = (byte)rnd.Next(256);
byte colB = (byte)rnd.Next(256);
DrawRectangle(bitmap, (size + 1) * x, (size + 1) * y, size, size, Color.FromRgb(colR, colG, colB));
}
}
bitmap.Unlock(); // Lock() and Unlock() could be moved to the DrawRectangle() method. Just do some performance tests.
image.Source = bitmap; // This should be done only once
}
int pBackBuffer = (int)writeableBitmap.BackBuffer;
替换为 var pBackBuffer = writeableBitmap.BackBuffer
。此外,您可以通过将 *((int*)pBackBuffer) = colorData;
替换为 Marshal.WriteInt32(pBackBuffer, colorData)
来删除对 unsafe
的要求。 - Simon Mourier