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Bitmap.LockBits Method (Rectangle, ImageLockMode, PixelFormat)

Locks a Bitmap into system memory.

Namespace: System.Drawing
Assembly: System.Drawing (in system.drawing.dll)

public BitmapData LockBits (
	Rectangle rect,
	ImageLockMode flags,
	PixelFormat format
)
public BitmapData LockBits (
	Rectangle rect, 
	ImageLockMode flags, 
	PixelFormat format
)
public function LockBits (
	rect : Rectangle, 
	flags : ImageLockMode, 
	format : PixelFormat
) : BitmapData
Not applicable.

Parameters

rect

A Rectangle structure specifying the portion of the Bitmap to lock.

flags

An ImageLockMode enumeration specifying the access level (read/write) for the Bitmap.

format

A PixelFormat enumeration specifying the data format of this Bitmap.

Return Value

A BitmapData containing information about this lock operation.

Exception typeCondition

ArgumentException

The PixelFormat is not a specific bits-per-pixel value.

-or-

The incorrect PixelFormat is passed in for a bitmap.

Exception

The operation failed.

The BitmapData specifies the attributes of the Bitmap, such as size, pixel format, the starting address of the pixel data in memory, and length of each scan line (stride).

When calling this method, you should use a member of the System.Drawing.Imaging.PixelFormat enumeration that contains a specific bits-per-pixel (BPP) value. Using System.Drawing.Imaging.PixelFormat values such as Indexed and Gdi will throw an.System.ArgumentException. Also, passing the incorrect pixel format for a bitmap will throw an System.ArgumentException.

The following code example demonstrates how to use the PixelFormat, Height, Width, and Scan0 properties; the LockBits and UnlockBits methods; and the ImageLockMode enumeration. This example is designed to be used with Windows Forms. To run this example, paste it into a form and handle the form's Paint event by calling the LockUnlockBitsExample method, passing e as PaintEventArgs.

private void LockUnlockBitsExample(PaintEventArgs e)
{

    // Create a new bitmap.
    Bitmap bmp = new Bitmap("c:\\fakePhoto.jpg");

    // Lock the bitmap's bits.  
    Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
    System.Drawing.Imaging.BitmapData bmpData = 
        bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,
        bmp.PixelFormat);
          
    // Get the address of the first line.
   IntPtr ptr = bmpData.Scan0;

    // Declare an array to hold the bytes of the bitmap.
    // This code is specific to a bitmap with 24 bits per pixels.
    int bytes = bmp.Width * bmp.Height * 3;
    byte[] rgbValues = new byte[bytes];

    // Copy the RGB values into the array.
    System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);

    // Set every red value to 255.  
    for (int counter = 2; counter < rgbValues.Length; counter+=3)
        rgbValues[counter] = 255;
  
    // Copy the RGB values back to the bitmap
    System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);

    // Unlock the bits.
    bmp.UnlockBits(bmpData);

    // Draw the modified image.
    e.Graphics.DrawImage(bmp, 0, 150);

}

private void LockUnlockBitsExample(PaintEventArgs e)
{
    // Create a new bitmap.
    Bitmap bmp = new Bitmap("c:\\fakePhoto.jpg");

    // Lock the bitmap's bits.  
    Rectangle rect = new Rectangle(0, 0, bmp.get_Width(), bmp.get_Height());
    System.Drawing.Imaging.BitmapData bmpData = bmp.LockBits(rect, 
        System.Drawing.Imaging.ImageLockMode.ReadWrite, 
        bmp.get_PixelFormat());

    // Get the address of the first line.
    IntPtr ptr = bmpData.get_Scan0();

    // Declare an array to hold the bytes of the bitmap.
    // This code is specific to a bitmap with 24 bits per pixels.
    int bytes = bmp.get_Width() * bmp.get_Height() * 3;
    ubyte rgbValues[] = new ubyte[bytes];

    // Copy the RGB values into the array.
    System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);

    // Set every red value to 255.  
    for (int counter = 2; counter < rgbValues.get_Length(); counter+=3) {
        rgbValues[counter] = 255;
    }

    // Copy the RGB values back to the bitmap
    System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);

    // Unlock the bits.
    bmp.UnlockBits(bmpData);

    // Draw the modified image.
    e.get_Graphics().DrawImage(bmp, 0, 150);
} //LockUnlockBitsExample

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0

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