HOW TO：使用 LockBits
更新：2007 年 11 月
.NET Compact Framework 提供 LockBits 方法的支援，這個方法可讓您在未受管理的記憶體緩衝區中操作點陣圖的像素陣列，然後將點陣圖中的像素換成來自緩衝區的像素。
.NET Compact Framework 不支援採取 BitmapData 做為參數的 LockBits 多載。您可以對 ImageLockMode 使用 ReadWrite、ReadOnly 和 WriteOnly 值。.NET Compact Framework 僅支援下列 PixelFormat 值。
請注意，.NET Compact Framework 不支援 Image 的 PixelFormat 屬性，您必須使用 LockBits 中的 format 參數明確指定其像素格式值。
範例
下列範例會建立點陣圖，並使用 LockBits 來變更一系列藍色像素的濃度。
'Call method from OnPaint.
Protected Overrides Sub OnPaint(e As PaintEventArgs)
LockUnlockBits(e)
End Sub
Private Sub LockUnlockBits(e As PaintEventArgs)
Dim bmp As New Bitmap(".\test.bmp")
' Specify a pixel format.
Dim pxf As PixelFormat = Pixelformat.Format24bppRgb
' Lock the bitmap's bits.
Dim rect As Rectangle = New Rectangle(0,0,bmp.Width,Bmp.Height)
Dim bmpData As BitmapData = bmp.LockBits(rect, _
ImageLockMOde.ReadWrite, pxf)
'Get the address of the first line of the bitmap.
Dim ptr As IntPtr = bmpData.Scan0
' Declare an array to hold the bytes of the bitmap.
' Dim numBytes as Integer = bmp.Width * bmp.Height * 3
Dim numBytes as Integer = bmpData.Stride * bmp.Height
Dim rgbValues(numBytes) As Byte
' Copy the RGB values into the array.
Marshal.Copy(ptr, rgbValues, 0, numBytes)
' Manipulate the bitmap, such as changing the
' blue value for every other pixel in the the bitmap.
For counter As Integer = 0 To rgbValues.Length Step 6
rgbValues(counter) = 255
Next counter
' Copy the RGB values back to the bitmap
Marshal.Copy(rgbValues, 0, ptr, numBytes)
' Unlock the bits.
bmp.UnlockBits(bmpData)
' Draw the modified image.
e.Graphics.DrawImage(bmp, 0, 0)
e.Graphics.Dispose()
End Sub
private Bitmap CreateBitmap(int width, int height, string s)
{
Bitmap bmp = new Bitmap(width, height);
Graphics g = Graphics.FromImage(bmp);
g.FillRectangle(new SolidBrush(Color.LightCoral), 0, 0, bmp.Width, bmp.Height);
g.DrawRectangle(new Pen(Color.Green, 10), 5, 5, bmp.Width - 10, bmp.Height - 10);
g.DrawLine(new Pen(Color.Yellow, 15), 0, 0, bmp.Width, bmp.Height);
g.DrawLine(new Pen(Color.Yellow, 15), bmp.Width, 0, 0, bmp.Height);
SizeF size = g.MeasureString(s, this.Font);
g.DrawString(s, this.Font, new SolidBrush(Color.Black),
(bmp.Width - size.Width) / 2,
(bmp.Height - size.Height) / 2);
g.Dispose();
return bmp;
}
protected override void OnPaint(PaintEventArgs e)
{
Bitmap bmp = CreateBitmap(100, 100, "Hi Mom!");
e.Graphics.DrawImage(bmp, 0, 0);
MakeMoreBlue(bmp);
// Draw the modified image to the right of the original one
e.Graphics.DrawImage(bmp, 120, 0);
bmp.Dispose();
}
private void MakeMoreBlue(Bitmap bmp)
{
// Specify a pixel format.
PixelFormat pxf = PixelFormat.Format24bppRgb;
// Lock the bitmap's bits.
Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
BitmapData bmpData =
bmp.LockBits(rect, ImageLockMode.ReadWrite,
pxf);
// Get the address of the first line.
IntPtr ptr = bmpData.Scan0;
// Declare an array to hold the bytes of the bitmap.
// int numBytes = bmp.Width * bmp.Height * 3;
int numBytes = bmpData.Stride * bmp.Height;
byte[] rgbValues = new byte[numBytes];
// Copy the RGB values into the array.
Marshal.Copy(ptr, rgbValues, 0, numBytes);
// Manipulate the bitmap, such as changing the
// blue value for every other pixel in the the bitmap.
for(int counter = 0; counter < rgbValues.Length; counter+=6)
rgbValues[counter] = 255;
// Copy the RGB values back to the bitmap
Marshal.Copy(rgbValues, 0, ptr, numBytes);
// Unlock the bits.
bmp.UnlockBits(bmpData);
}
編譯程式碼
這個範例需要下列命名空間的參考：