/// <summary> /// 将源图像灰度化，但是没有转化为8位灰度图像。 /// http://www.bobpowell.net/grayscale.htm /// </summary> /// <param name="original"> 源图像。 </param> /// <returns> 灰度RGB图像。 </returns> public static Bitmap MakeGrayScale(Bitmap original) { //create a blank bitmap the same size as original Bitmap newBitmap = new Bitmap(original.Width, original.Height, PixelFormat.Format24bppRgb); //get a graphics object from the new image Graphics g = Graphics.FromImage(newBitmap); //create the grayscale ColorMatrix ColorMatrix colorMatrix = new ColorMatrix( new float[][] { new float[] { .3f, .3f, .3f, 0, 0 }, new float[] { .59f, .59f, .59f, 0, 0 }, new float[] { .11f, .11f, .11f, 0, 0 }, new float[] { 0, 0, 0, 1, 0 }, new float[] { 0, 0, 0, 0, 1 } }); /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * ┌ ┐ │ 0.3 0.3 0.3 0 0 │ │ 0.59 0.59 0.59 0 0 │ │ 0.11 0.11 0.11 0 0 │ │ 0 0 0 1 0 │ │ 0 0 0 0 1 │ └ ┘ * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ //create some image attributes ImageAttributes attributes = new ImageAttributes(); //set the color matrix attribute attributes.SetColorMatrix(colorMatrix); //draw the original image on the new image //using the grayscale color matrix g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height), 0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes); //dispose the Graphics object g.Dispose(); return newBitmap; } /// <summary> /// 将源图像灰度化，并转化为8位灰度图像。 /// </summary> /// <param name="original"> 源图像。 </param> /// <returns> 8位灰度图像。 </returns> public static Bitmap RgbToGrayScale(Bitmap original) { if (original != null) { // 将源图像内存区域锁定 Rectangle rect = new Rectangle(0, 0, original.Width, original.Height); BitmapData bmpData = original.LockBits(rect, ImageLockMode.ReadOnly, original.PixelFormat); // 获取图像参数 int width = bmpData.Width; int height = bmpData.Height; int stride = bmpData.Stride; // 扫描线的宽度 int offset = stride - width * 3; // 显示宽度与扫描线宽度的间隙 IntPtr ptr = bmpData.Scan0; // 获取bmpData的内存起始位置 int scanBytes = stride * height; // 用stride宽度，表示这是内存区域的大小 // 分别设置两个位置指针，指向源数组和目标数组 int posScan = 0, posDst = 0; byte[] rgbValues = new byte[scanBytes]; // 为目标数组分配内存 Marshal.Copy(ptr, rgbValues, 0, scanBytes); // 将图像数据拷贝到rgbValues中 // 分配灰度数组 byte[] grayValues = new byte[width * height]; // 不含未用空间。 // 计算灰度数组 for (int i = 0; i < height; i++) { for (int j = 0; j < width; j++) { double temp = rgbValues[posScan++] * 0.11 + rgbValues[posScan++] * 0.59 + rgbValues[posScan++] * 0.3; grayValues[posDst++] = (byte)temp; } // 跳过图像数据每行未用空间的字节，length = stride - width * bytePerPixel posScan += offset; } // 内存解锁 Marshal.Copy(rgbValues, 0, ptr, scanBytes); original.UnlockBits(bmpData); // 解锁内存区域 // 构建8位灰度位图 Bitmap retBitmap = BuiltGrayBitmap(grayValues, width, height); return retBitmap; } else { return null; } } /// <summary> /// 用灰度数组新建一个8位灰度图像。 /// http://www.cnblogs.com/spadeq/archive/2009/03/17/1414428.html /// </summary> /// <param name="rawValues"> 灰度数组(length = width * height)。 </param> /// <param name="width"> 图像宽度。 </param> /// <param name="height"> 图像高度。 </param> /// <returns> 新建的8位灰度位图。 </returns> private static Bitmap BuiltGrayBitmap(byte[] rawValues, int width, int height) { // 新建一个8位灰度位图，并锁定内存区域操作 Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format8bppIndexed); BitmapData bmpData = bitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed); // 计算图像参数 int offset = bmpData.Stride - bmpData.Width; // 计算每行未用空间字节数 IntPtr ptr = bmpData.Scan0; // 获取首地址 int scanBytes = bmpData.Stride * bmpData.Height; // 图像字节数 = 扫描字节数 * 高度 byte[] grayValues = new byte[scanBytes]; // 为图像数据分配内存 // 为图像数据赋值 int posSrc = 0, posScan = 0; // rawValues和grayValues的索引 for (int i = 0; i < height; i++) { for (int j = 0; j < width; j++) { grayValues[posScan++] = rawValues[posSrc++]; } // 跳过图像数据每行未用空间的字节，length = stride - width * bytePerPixel posScan += offset; } // 内存解锁 Marshal.Copy(grayValues, 0, ptr, scanBytes); bitmap.UnlockBits(bmpData); // 解锁内存区域 // 修改生成位图的索引表，从伪彩修改为灰度 ColorPalette palette; // 获取一个Format8bppIndexed格式图像的Palette对象 using (Bitmap bmp = new Bitmap(1, 1, PixelFormat.Format8bppIndexed)) { palette = bmp.Palette; } for (int i = 0; i < 256; i++) { palette.Entries[i] = Color.FromArgb(i, i, i); } // 修改生成位图的索引表 bitmap.Palette = palette; return bitmap; }
速度最快 public static unsafe void ConvertTo8BitBitmap(Bitmap img, string destFile) { var bit = new Bitmap(img.Width, img.Height, PixelFormat.Format8bppIndexed); BitmapData data = img.LockBits(new Rectangle(0, 0, img.Width, img.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb); var bp = (byte*)data.Scan0.ToPointer(); BitmapData data2 = bit.LockBits(new Rectangle(0, 0, bit.Width, bit.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed); var bp2 = (byte*)data2.Scan0.ToPointer(); for (int i = 0; i != data.Height; i++) { for (int j = 0; j != data.Width; j++) { //0.3R+0.59G+0.11B float value = 0.11F * bp[i * data.Stride + j * 3] + 0.59F * bp[i * data.Stride + j * 3 + 1] + 0.3F * bp[i * data.Stride + j * 3 + 2]; bp2[i * data2.Stride + j] = (byte)value; } } img.UnlockBits(data); bit.UnlockBits(data2); ColorPalette palette = bit.Palette; for (int i = 0; i != palette.Entries.Length; i++) { palette.Entries[i] = Color.FromArgb(i, i, i); } bit.Palette = palette; bit.Save(destFile, ImageFormat.Bmp); img.Dispose(); bit.Dispose(); } bp[i * data.Stride + j * 3]