C#【图像处理】关于LockBitmap的使用，（内存法）

转自https://www.cnblogs.com/bomo/archive/2013/02/26/2934055.html

在处理较多的数据时，Bitmap中的Set/Get等函数在处理数据时比较慢，如果用内存法或者指针法会加快处理速度，这里只学习了内存法，做一个记录。
首先我们在对Bitmap中的数据进行处理时，应当锁定当前bitmap，把图像数据复制到一个内存中，对内存中的数据进行处理，一系列算法完成后，再把算出来的RGB数据放入开始复制的内存数据中，而后复制到图像数据。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

namespace WindowsFormsApplication1
{
public class LockBitmap
{
Bitmap source = null;
IntPtr Iptr = IntPtr.Zero;
BitmapData bitmapData = null;

public byte[] Pixels { get; set; }
public int Depth { get; private set; }
public int Width { get; private set; }
public int Height { get; private set; }

public LockBitmap(Bitmap source)
{
this.source = source;
}

/// <summary>
/// Lock bitmap data
/// </summary>
public void LockBits()//传入bmp，
{
try
{
// Get width and height of bitmap
Width = source.Width;
Height = source.Height;

// get total locked pixels count
int PixelCount = Width * Height;//像素

// Create rectangle to lock
Rectangle rect = new Rectangle(0, 0, Width, Height);//指定要锁定的部分

// get source bitmap pixel format size检验是否是8.24.32位图像
Depth = System.Drawing.Bitmap.GetPixelFormatSize(source.PixelFormat);

// Check if bpp (Bits Per Pixel) is 8, 24, or 32
if (Depth != 8 && Depth != 24 && Depth != 32)
{
throw new ArgumentException("Only 8, 24 and 32 bpp images are supported.");
}

// Lock bitmap and return bitmap data
bitmapData = source.LockBits(rect, ImageLockMode.ReadWrite,
source.PixelFormat);

// create byte array to copy pixel values
int step = Depth / 8;
Pixels = new byte[PixelCount * step];//如果是24位，像素*3=所有RGB数组组。
Iptr = bitmapData.Scan0;//指针放到第一个数据。也就是第一个像素的B

// Copy data from pointer to array
Marshal.Copy(Iptr, Pixels, 0, Pixels.Length);//复制到Pixel，传入bmp的数据复制到Pixel数组
}
catch (Exception ex)
{
throw ex;
}
}

/// <summary>
/// Unlock bitmap data
/// </summary>
public void UnlockBits()
{
try
{
// Copy data from byte array to pointer
Marshal.Copy(Pixels, 0, Iptr, Pixels.Length);

// Unlock bitmap data
source.UnlockBits(bitmapData);
}
catch (Exception ex)
{
throw ex;
}
}

/// <summary>
/// Get the color of the specified pixel
/// </summary>
/// <param name="x"></param>
/// <param name="y"></param>
/// <returns></returns>
public Color LockGetPixel(int x, int y)
{
Color clr = Color.Empty;

// Get color components count
int cCount = Depth / 8;//Depth表示多少位数据

// Get start index of the specified pixel//获得指定像素的起始索引
int i = ((y * Width) + x) * cCount;

if (i > Pixels.Length - cCount)
throw new IndexOutOfRangeException();//抛出新异常

if (Depth == 32) // For 32 bpp get Red, Green, Blue and Alpha
{
byte b = Pixels[i];
byte g = Pixels[i + 1];
byte r = Pixels[i + 2];
byte a = Pixels[i + 3]; // a
clr = Color.FromArgb(a, r, g, b);
}
if (Depth == 24) // For 24 bpp get Red, Green and Blue
{
byte b = Pixels[i];
byte g = Pixels[i + 1];
byte r = Pixels[i + 2];
clr = Color.FromArgb(r, g, b);
}
if (Depth == 8)
// For 8 bpp get color value (Red, Green and Blue values are the same)
{
byte c = Pixels[i];
clr = Color.FromArgb(c, c, c);
}
return clr;
}

/// <summary>
/// Set the color of the specified pixel
/// </summary>
/// <param name="x"></param>
/// <param name="y"></param>
/// <param name="color"></param>
public void LockSetPixel(int x, int y, Color color)
{
// Get color components count
int cCount = Depth / 8;

// Get start index of the specified pixel
int i = ((y * Width) + x) * cCount;

if (Depth == 32) // For 32 bpp set Red, Green, Blue and Alpha
{
Pixels[i] = color.B;
Pixels[i + 1] = color.G;
Pixels[i + 2] = color.R;
Pixels[i + 3] = color.A;
}
if (Depth == 24) // For 24 bpp set Red, Green and Blue
{
Pixels[i] = color.B;
Pixels[i + 1] = color.G;
Pixels[i + 2] = color.R;
}
if (Depth == 8)
// For 8 bpp set color value (Red, Green and Blue values are the same)
{
Pixels[i] = color.B;
}
}
}
}