10.WPF WriteableBitmap的簡單應用

摘要： 新建一個WPF專案 reference：https://docs.microsoft.com/zh-cn/dotnet/api/system.windows.media.imaging.writeablebitmap?view=netframework-...

新建一個WPF專案

reference：https://docs.microsoft.com/zh-cn/dotnet/api/system.windows.media.imaging.writeablebitmap?view=netframework-4.7.2

刪除MainWindow

刪除App.xaml

新增指令碼 Program.cs

專案屬性-》Application -》Startup object改為xxx.Program

Program指令碼如下：

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Input;

namespace WpfApp4
{
class Program
{
static WriteableBitmap writeableBitmap;
static Window w;
static Image i;

[STAThread]
static void Main(string[] args)
{
i = new Image();
RenderOptions.SetBitmapScalingMode(i, BitmapScalingMode.NearestNeighbor);
RenderOptions.SetEdgeMode(i, EdgeMode.Aliased);

w = new Window();
w.Content = i;
w.Show();

writeableBitmap = new WriteableBitmap(
(int)w.ActualWidth,
(int)w.ActualHeight,
96,
96,
PixelFormats.Bgr32,
null);

i.Source = writeableBitmap;

i.Stretch = Stretch.None;
i.HorizontalAlignment = HorizontalAlignment.Left;
i.VerticalAlignment = VerticalAlignment.Top;

i.MouseMove += new MouseEventHandler(i_MouseMove);
i.MouseLeftButtonDown +=
new MouseButtonEventHandler(i_MouseLeftButtonDown);
i.MouseRightButtonDown +=
new MouseButtonEventHandler(i_MouseRightButtonDown);

w.MouseWheel += new MouseWheelEventHandler(w_MouseWheel);

Application app = new Application();
app.Run();
}

// The DrawPixel method updates the WriteableBitmap by using
// unsafe code to write a pixel into the back buffer.
static void DrawPixel(MouseEventArgs e)
{
int column = (int)e.GetPosition(i).X;
int row = (int)e.GetPosition(i).Y;

try
{
// Reserve the back buffer for updates.
writeableBitmap.Lock();

unsafe
{
// Get a pointer to the back buffer.
int pBackBuffer = (int)writeableBitmap.BackBuffer;

// Find the address of the pixel to draw.
pBackBuffer += row * writeableBitmap.BackBufferStride;
pBackBuffer += column * 4;

// Compute the pixel's color.
int color_data = 255 << 16; // R
color_data |= 128 << 8;// G
color_data |= 255 << 0;// B

// Assign the color data to the pixel.
*((int*)pBackBuffer) = color_data;
}

// Specify the area of the bitmap that changed.
writeableBitmap.AddDirtyRect(new Int32Rect(column, row, 1, 1));
}
finally
{
// Release the back buffer and make it available for display.
writeableBitmap.Unlock();
}
}

static void ErasePixel(MouseEventArgs e)
{
byte[] ColorData = { 0, 0, 0, 0 }; // B G R

Int32Rect rect = new Int32Rect(
(int)(e.GetPosition(i).X),
(int)(e.GetPosition(i).Y),
1,
1);

writeableBitmap.WritePixels(rect, ColorData, 4, 0);
}

static void i_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
ErasePixel(e);
}

static void i_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
DrawPixel(e);
}

static void i_MouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
DrawPixel(e);
}
else if (e.RightButton == MouseButtonState.Pressed)
{
ErasePixel(e);
}
}

static void w_MouseWheel(object sender, MouseWheelEventArgs e)
{
System.Windows.Media.Matrix m = i.RenderTransform.Value;

if (e.Delta > 0)
{
m.ScaleAt(
1.5,
1.5,
e.GetPosition(w).X,
e.GetPosition(w).Y);
}
else
{
m.ScaleAt(
1.0 / 1.5,
1.0 / 1.5,
e.GetPosition(w).X,
e.GetPosition(w).Y);
}

i.RenderTransform = new MatrixTransform(m);
}
}
}