C#【圖像處理】關於LockBitmap的使用，（記憶體法）

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

在處理較多的數據時，Bitmap中的Set/Get等函數在處理數據時比較慢，如果用記憶體法或者指針法會加快處理速度，這裡只學習了記憶體法，做一個記錄。
首先我們在對Bitmap中的數據進行處理時，應當鎖定當前bitmap，把圖像數據複製到一個記憶體中，對記憶體中的數據進行處理，一系列演算法完成後，再把算出來的RGB數據放入開始複製的記憶體數據中，而後複製到圖像數據。
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()//傳入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);//指定要鎖定的部分

// get source bitmap pixel format size檢驗是否是8.24.32點陣圖像
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數組組。
Iptr = bitmapData.Scan0;//指針放到第一個數據。也就是第一個像素的B

// Copy data from pointer to array
Marshal.Copy(Iptr, Pixels, 0, Pixels.Length);//複製到Pixel，傳入bmp的數據複製到Pixel數組
}
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表示多少位數據

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

if (i > Pixels.Length - cCount)
throw new IndexOutOfRangeException();//拋出新異常

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;
}
}
}
}