1、c#图像处理入门的一个好方法 c#图像处理入门的一个好方法-bitmap类和图像像素值获取方法 一Bitmap类Bitmap对象封装了+中的一个位图，此位图由图形图像及其属性的像素数据组成.因此Bitmap是用于处理由像素数据定义的图像的对象.该类的主要方法和属性如下：1. GetPixel方法和 SetPixel方法：获取和设置一个图像的指定像素的颜色.2. PixelFormat属性：返回图像的像素格式.3. Palette属性：获取和设置图像所使用的颜色调色板.4. Height Width属性：返回图像的高度和宽度.5. LockBits 方法和UnlockBits方法：分别锁定和解锁
2、系统内存中的位图像素.在基于像素点的图像处理方法中使用LockBits 和UnlockBits是一个很好的方式，这两种方法可以使我们指定像素的范围来控制位图的任意一部分，从而消除了通过循环对位图的像素逐个进行处理，每调用LockBits 之后都应该调用一次UnlockBits. 二BitmapData类BitmapData对象指定了位图的属性1. Height属性：被锁定位图的高度.2. Width属性：被锁定位图的高度.3. PixelFormat属性：数据的实际像素格式.4. Scan0属性：被锁定数组的首字节地址，如果整个图像被锁定，则是图像的第一个字节地址.5. Stride属性：步幅
3、，也称为扫描宽度.如上图所示,数组的长度并不一定等于图像像素数组的长度,还有一部分未用区域,这涉及到位图的数据结构,系统要保证每行的字节数必须为4的倍数. 三Graphics类Graphics对象是+的关键所在，许多对象都是由Graphics类表示的，该类定义了绘制和填充图形对象的方法和属性，一个应用程序只要需要进行绘制或着色，它就必须使用Graphics对象. 四Image类这个类提供了位图和元文件操作的函数.Image类被声明为abstract,也就是说Image类不能实例化对象,而只能做为一个基类.1.FromFile方法：它根据输入的文件名产生一个Image对象,它有两种函数形式:pu
4、blic static Image FromFile(string filename);public static Image FromFile(string filename, bool useEmbeddedColorManagement);2.FromHBitmap方法：它从一个windows句柄处创建一个bitmap对象, 它也包括两种函数形式:public static bitmap fromhbitmap(intptr hbitmap);public static bitmap fromhbitmap(intptr hbitmap, intptr hpalette);3. From
5、Stream方法：从一个数据流中创建一个image对象,它包含三种函数形式 :public static image fromstream(stream stream);public static image fromstream(stream stream, bool useembeddedcolormanagement);fromstream(stream stream, bool useembeddedcolormanagement, bool validateimagedata); 有了上面的了解，我们便可以开始利用#做图像处理，下面介绍几种方法：一. 打开、保存、显示图像 priva
6、te Bitmap srcBitmap = null; private Bitmap showBitmap = null; /打开文件 private void menuFileOpen_Click(object sender, EventArgs e) OpenFileDialog openFileDialog = new OpenFileDialog(); openFileDialog.Filter = Bitmap文件(*.bmp)|*.bmp|Jpeg文件(*.jpg)|*.jpg|所有合适文件(*.bmp,*.jpg)|*.bmp;*.jpg; openFileDialog.Filt
7、erIndex = 3; openFileDialog.RestoreDirectory = true; if (DialogResult.OK = openFileDialog.ShowDialog() srcBitmap = (Bitmap)Bitmap.FromFile(openFileDialog.FileName, false); showBitmap = srcBitmap; this.AutoScroll = true; this.AutoScrollMinSize = new Size(int)(showBitmap.Width), (int)(showBitmap.Heigh
8、t); this.Invalidate(); /保存图像文件 private void menuFileSave_Click(object sender, EventArgs e) if (showBitmap != null) SaveFileDialog saveFileDialog = new SaveFileDialog(); saveFileDialog.Filter = Bitmap文件(*.bmp)|*.bmp|Jpeg文件(*.jpg)|*.jpg|所有合适文件(*.bmp,*.jpg)|*.bmp;*.jpg; saveFileDialog.FilterIndex = 3;
9、saveFileDialog.RestoreDirectory = true; if (DialogResult.OK = saveFileDialog.ShowDialog() ImageFormat format = ImageFormat.Jpeg; switch (Path.GetExtension(saveFileDialog.FileName).ToLower() case .jpg: format = ImageFormat.Jpeg; break; case .bmp: format = ImageFormat.Bmp; break; default: MessageBox.S
10、how(this, Unsupported image format was specified, Error, MessageBoxButtons.OK, MessageBoxIcon.Error); return; try showBitmap.Save(saveFileDialog.FileName,format ); catch (Exception) MessageBox.Show(this, Failed writing image file, Error, MessageBoxButtons.OK, MessageBoxIcon.Error); /窗口重绘,在窗体上显示图像,重载
11、Paint private void frmMain_Paint(object sender, System.Windows.Forms.PaintEventArgs e) if (showBitmap != null) Graphics g = e.Graphics; g.DrawImage(showBitmap, new Rectangle(this.AutoScrollPosition.X, this.AutoScrollPosition.Y , (int)(showBitmap.Width), (int)(showBitmap.Height); /灰度化 private void me
12、nu2Gray_Click(object sender, EventArgs e) if (showBitmap = null) return; showBitmap = RGB2Gray(showBitmap);/下面都以RGB2Gray为例 this.Invalidate(); 二. 提取像素法 这种方法简单易懂,但相当耗时,完全不可取.public static Bitmap RGB2Gray(Bitmap srcBitmap) Color srcColor; int wide = srcBitmap.Width; int height = srcBitmap.Height; for (
13、int y = 0; y < height; y+) for (int x = 0; x < wide; x+) /获取像素的颜色值 srcColor = srcBitmap.GetPixel(x, y); byte temp = (byte)(srcColor.R * .299 + srcColor.G * .587 + srcColor.B * .114); /设置像素的颜色值 srcBitmap.SetPixel(x, y, Color.FromArgb(temp, temp, temp); return srcBitmap ; /# 三. 内存法这是比较常用的方法publi
14、c static Bitmap RGB2Gray(Bitmap srcBitmap) int wide = srcBitmap.Width; int height = srcBitmap.Height; Rectangle rect = new Rectangle(0, 0, wide, height); / 将Bitmap锁定到系统内存中, 获得BitmapData BitmapData srcBmData = srcBitmap.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); /创建Bitmap Bi
15、tmap dstBitmap = CreateGrayscaleImage(wide, height);/这个函数在后面有定义 BitmapData dstBmData = dstBitmap.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed); / 位图中第一个像素数据的地址。它也可以看成是位图中的第一个扫描行 System.IntPtr srcPtr = srcBmData.Scan0; System.IntPtr dstPtr = dstBmData.Scan0; / 将Bitmap对象的信息存放到
16、byte数组中 int src_bytes = srcBmData.Stride * height; byte srcValues = new bytesrc_bytes; int dst_bytes = dstBmData.Stride * height; byte dstValues = new bytedst_bytes; /复制GRB信息到byte数组 System.Runtime.InteropServices.Marshal.Copy(srcPtr, srcValues, 0, src_bytes); System.Runtime.InteropServices.Marshal.C
17、opy(dstPtr, dstValues, 0, dst_bytes); / 根据Y=0.299*R+0.114*G+0.587B,Y为亮度 for (int i = 0; i < height; i+) for (int j = 0; j < wide; j+) /只处理每行中图像像素数据,舍弃未用空间 /注意位图结构中RGB按BGR的顺序存储 int k = 3 * j; byte temp = (byte)(srcValuesi * srcBmData.Stride + k + 2 * .299 + srcValuesi * srcBmData.Stride + k + 1
18、 * .587 + srcValuesi * srcBmData.Stride + k * .114); dstValuesi * dstBmData.Stride + j = temp; /将更改过的byte拷贝到原位图 System.Runtime.InteropServices.Marshal.Copy(dstValues, 0, dstPtr, dst_bytes); / 解锁位图 srcBitmap.UnlockBits(srcBmData); dstBitmap.UnlockBits(dstBmData); return dstBitmap; /# 四 指针法C/C+的习惯,不是C
19、#的特点public static Bitmap RGB2Gray(Bitmap srcBitmap) int wide = srcBitmap.Width; int height = srcBitmap.Height ; Rectangle rect = new Rectangle(0, 0, wide, height); BitmapData srcBmData = srcBitmap.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); Bitmap dstBitmap = CreateGrayscale
20、Image(wide, height); BitmapData dstBmData = dstBitmap.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed); System.IntPtr srcScan = srcBmData.Scan0; System.IntPtr dstScan = dstBmData.Scan0; Unsafe /启动不安全代码 byte* srcP = (byte*)(void*) srcScan; byte* dstP = (byte*)(void*) dstScan; in
21、t srcOffset = srcBmData.Stride - wide * 3; int dstOffset = dstBmData.Stride - wide ; byte red, green, blue; for (int y = 0; y < height; y+) for (int x = 0; x <wide ; x+, srcP += 3, dstP+) blue = srcP 0; green = srcP 1; red = srcP 2; * dstP = (byte)(.299 * red + .587 * green + .114 * blue); src
22、P += srcOffset; dstP += dstOffset; srcBitmap.UnlockBits(srcBmData); dstBitmap.UnlockBits(dstBmData ); return dstBitmap; /#五. 矩阵法并不是什么新方法,只是将图像数据分做R,G,B三个矩阵(二维数组)存储,类似MATLAB的习惯. public static bool GetRGB(Bitmap Source, out int, R, out int, G, out int, B) try int iWidth = Source.Width; int iHeight = S
23、ource.Height; Rectangle rect = new Rectangle(0, 0, iWidth, iHeight); System.Drawing.Imaging.BitmapData bmpData = Source.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, Source.PixelFormat); IntPtr iPtr = bmpData.Scan0; int iBytes = iWidth * iHeight * 3; byte PixelValues = new byteiByte
24、s; System.Runtime.InteropServices.Marshal.Copy(iPtr, PixelValues, 0, iBytes); Source.UnlockBits(bmpData); / 注意这个地方图像的两维方向与数组两维的方向是转置的关系 R = new intiHeight, iWidth; G = new intiHeight, iWidth; B = new intiHeight, iWidth; int iPoint = 0; for (int i = 0; i < iHeight; i+) for (int j = 0; j < iWidt
25、h; j+) / 注意，Windows 中三基色的排列顺序是 BGR 而不是 RGB！ Bi, j = Convert.ToInt32(PixelValuesiPoint+); Gi, j = Convert.ToInt32(PixelValuesiPoint+); Ri, j = Convert.ToInt32(PixelValuesiPoint+); return true; catch (Exception) R = null; G = null; B = null; return false; /# public static Bitmap FromRGB(int, R, int, G
26、, int, B) int iWidth = G.GetLength(1); int iHeight = G.GetLength(0); Bitmap Result = new Bitmap(iWidth, iHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb); Rectangle rect = new Rectangle(0, 0, iWidth, iHeight); System.Drawing.Imaging.BitmapData bmpData = Result.LockBits(rect, System.Drawing
27、.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format24bppRgb); IntPtr iPtr = bmpData.Scan0; int iStride = bmpData.Stride; int iBytes = iWidth * iHeight * 3; byte PixelValues = new byteiBytes; int iPoint = 0; for (int i = 0; i < iHeight; i+) for (int j = 0; j < iWidth; j+
28、) int iG = Gi, j; int iB = Bi, j; int iR = Ri, j; PixelValuesiPoint = Convert.ToByte(iB); PixelValuesiPoint + 1 = Convert.ToByte(iG); PixelValuesiPoint + 2 = Convert.ToByte(iR); iPoint += 3; System.Runtime.InteropServices.Marshal.Copy(PixelValues, 0, iPtr, iBytes); Result.UnlockBits(bmpData); return
29、 Result; /# public static bool GetGray(Bitmap srcBitmap, out byte , gray) Bitmap tempBitmap; if (srcBitmap.PixelFormat != PixelFormat.Format8bppIndexed) tempBitmap = ImageProcess.Image.Gray(srcBitmap); else tempBitmap = srcBitmap; int wide = tempBitmap.Width; int height = tempBitmap.Height; gray = n
30、ew byte height, wide; BitmapData gbmData = tempBitmap.LockBits(new Rectangle(0, 0, wide, height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed); System.IntPtr ScanG = gbmData.Scan0; int gOffset = gbmData.Stride - wide; unsafe byte* g = (byte*)(void*)ScanG; / for each pixel for (int y = 0;
31、y < height; y+) / for each pixel for (int x = 0; x < wide; x+, g+) grayy ,x =*g; g += gOffset; tempBitmap.UnlockBits(gbmData); return true ; /# public static Bitmap FromGray(byte , Gray) int iWidth = Gray.GetLength(1); int iHeight = Gray.GetLength(0); Bitmap dstBitmap = ImageProcess.Image.CreateGrayscaleImage(iWidth, iHeight); BitmapData gbmData = dstBitmap.LockBits(new Rectangle(0, 0, iWidth, iHeight), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed); System.I
