如何在 C# 中以像素级别操作图像？
我需要能够分别读取/修改每个位图像素 RGB 值。
代码示例将不胜感激。
示例代码例程（我将其用于简单的合并和比较功能。它需要两张图像并生成第三张灰度图像，显示两张图像之间的差异作为灰度色调级别。它越暗，差异越大。） :
public static Bitmap Diff(Bitmap src1, Bitmap src2, int x1, int y1, int x2, int y2, int width, int height)
{
Bitmap diffBM = new Bitmap(width, height, PixelFormat.Format24bppRgb);
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
//Get Both Colours at the pixel point
Color col1 = src1.GetPixel(x1 + x, y1 + y);
Color col2 = src2.GetPixel(x2 + x, y2 + y);
// Get the difference RGB
int r = 0, g = 0, b = 0;
r = Math.Abs(col1.R - col2.R);
g = Math.Abs(col1.G - col2.G);
b = Math.Abs(col1.B - col2.B);
// Invert the difference average
int dif = 255 - ((r+g+b) / 3);
// Create new grayscale RGB colour
Color newcol = Color.FromArgb(dif, dif, dif);
diffBM.SetPixel(x, y, newcol);
}
}
return diffBM;
}
Marc 的帖子 注释 LockBits 并使用它直接修改内存中的图像。如果性能是一个问题，我建议查看它而不是我发布的内容。谢谢马克！
System.Drawing.Bitmap 有一个 GetPixel(int x, int y) 公共方法，它返回一个 System.Drawing.Color 结构。该结构具有字节成员 R、G、B 和 A，您可以直接修改它们，然后再次在您的位图上调用 SetPixel(Color)。
不幸的是，这将相对较慢，但这是在 C# 中执行此操作的最简单方法。如果您经常处理单个像素并且发现性能不足，并且您需要更快的东西，您可以使用 LockBits ......但是它要复杂得多，因为您需要了解该颜色深度和类型的位结构，并使用位图的步幅等等......所以如果你觉得有必要，一定要找到一个好的教程！网上有几个，谷歌搜索“C# LockBits”会给你半打值得一读的东西。
如果性能至关重要，LockBits 的另一种替代方法是托管 DirectX。
有关更多信息，请参阅之前的 Stack Overflow 问题 Rendering graphics in C#
与 Lockbits 一样，您需要使用不安全关键字/编译器开关，但您可以获得高性能像素级访问权限。与使用普通的 Bitmap 类和 PictureBox 控件相比，您还可以通过 DirectX 后备缓冲获得更高性能的屏幕渲染。
namespace GreekPicturePixelEditor
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private int X1 = 0; // picture box 1 mouse click X position
private int Y1 = 0; // picture box 1 mouse click y position
private bool mousePress = false; // is left mouse pressed in picture box 2
private Bitmap statueBitmap;
private SolidBrush brush;
private Pen pen;
private Rectangle rec;
private Color color;
private const int pSize = 20; // pixel size
// Step 1. Create first picture box 1 at least 512x512 pixel
// Create second picture box 2 at least 32x32 pixel
// Create a 512x512 bitmap image using MS Paint
// Load and display statue bitmap on picture box 1
private void Form1_Load(object sender, EventArgs e)
{
statueBitmap = new Bitmap(@"C:\VS2022\Pic\Greek512x512.bmp");
pictureBox1.Image = statueBitmap;
}
// Step 2. Save X1,Y1 mouse coordinate when user click on picture box 1
private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
{
X1 = e.X; // Save X1, Y1 mouse coordinate when user click on picture box 1
Y1 = e.Y;
pictureBox2.Refresh(); // force re-draw picture box 2
}
// Step 3. Create a 32x32 pixel grid on picture box 2. When user click on
// picture box 1, a pixel grid is created based on the X1,
// Y1 coordinate of picture box 2. In other words, 32x32 bitmap image
// is cloned starting at X1,Y1 position in picture box 1 to picture box 2.
private void pictureBox2_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
for( int px = 0; px < 31; px++ )
{
for( int py = 0; py < 31; py++ )
{
color = ((Bitmap)pictureBox1.Image).GetPixel( X1 + px, Y1 + py );
brush = new SolidBrush( color );
pen = new Pen( Form1.DefaultBackColor );
rec = new Rectangle( px * pSize, py * pSize, pSize, pSize );
g.FillRectangle( brush, rec );
g.DrawRectangle( pen, rec );
}
}
}
// Step 4. Handle mouse events when drawing picture box 2 with a mouse
private void pictureBox2_MouseUp(object sender, MouseEventArgs e)
{
mousePress = false;
}
// Step 4. Handle mouse events when drawing picture box 2 with a mouse
private void pictureBox2_MouseDown(object sender, MouseEventArgs e)
{
if( e.Button == MouseButtons.Left )
{
mousePress = true;
int X2 = e.X / 20; // Normalized the mouse position X and Y of picture box 2
int Y2 = e.Y / 20;
((Bitmap)pictureBox1.Image).SetPixel( X1 + X2, Y1 + Y2, System.Drawing.Color.Red );
pictureBox1.Refresh();
pictureBox2.Refresh();
}
}
// Step 4. Handle mouse events when drawing picture box 2 with a mouse
private void pictureBox2_MouseMove(object sender, MouseEventArgs e)
{
if( mousePress )
{
int X2 = e.X / 20; // Normalized the mouse position X and Y of picture box 2
int Y2 = e.Y / 20;
((Bitmap)pictureBox1.Image).SetPixel( X1 + X2, Y1 + Y2, System.Drawing.Color.Red );
pictureBox1.Refresh();
pictureBox2.Refresh();
}
}
// Step 5. Deallocate memory to the system
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
statueBitmap.Dispose();
brush.Dispose();
pen.Dispose() ;
}
}
}