最近用到这个FreeImage.DLL,之前只是在C++里面调用，现在需要在C#里调用，于是学习了一点点，总结一下：
在FreeImage中，要用到几个参数，在C#中定义如下：
private enum FREE_IMAGE_FORMAT{FIF_UNKNOWN = -1,FIF_BMP = 0,FIF_ICO = 1,FIF_JPEG = 2,FIF_JNG = 3,FIF_KOALA = 4,FIF_LBM = 5,FIF_IFF = FIF_LBM,FIF_MNG = 6,FIF_PBM = 7,FIF_PBMRAW = 8,FIF_PCD = 9,FIF_PCX = 10,FIF_PGM = 11,FIF_PGMRAW = 12,FIF_PNG = 13,FIF_PPM = 14,FIF_PPMRAW = 15,FIF_RAS = 16,FIF_TARGA = 17,FIF_TIFF = 18,FIF_WBMP = 19,FIF_PSD = 20,FIF_CUT = 21,FIF_XBM = 22,FIF_XPM = 23,FIF_DDS = 24,FIF_GIF = 25,FIF_HDR = 26}[StructLayout(LayoutKind.Sequential)]private struct RGBQUAD{internal byte Blue;internal byte Green;internal byte Red;internal byte Reserved;}
接下来，对DLL中的函数进行申明如下：
[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_Load@12", SetLastError = true)]private static extern IntPtr FreeImage_Load(FREE_IMAGE_FORMAT fif, string FileName, int Flag);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetFileType@8", SetLastError = true)]private static extern FREE_IMAGE_FORMAT FreeImage_GetFileType(string FileName, int Size);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetFIFFromFilename@4", SetLastError = true)]private static extern FREE_IMAGE_FORMAT FreeImage_GetFIFFromFilename(string FileName);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_FIFSupportsReading@4", SetLastError = true)]private static extern FREE_IMAGE_FORMAT FreeImage_FIFSupportsReading(FREE_IMAGE_FORMAT fif);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetWidth@4", SetLastError = true)]private static extern int FreeImage_GetWidth(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetHeight@4", SetLastError = true)]private static extern int FreeImage_GetHeight(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetPalette@4", SetLastError = true)]private static extern RGBQUAD* FreeImage_GetPalette(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetBPP@4", SetLastError = true)]private static extern int FreeImage_GetBPP(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetDIBSize@4", SetLastError = true)]private static extern int FreeImage_GetDIBSize(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetColorsUsed@4", SetLastError = true)]private static extern int FreeImage_GetColorsUsed(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetPitch@4", SetLastError = true)]private static extern int FreeImage_GetPitch(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_GetBits@4", SetLastError = true)]private static extern IntPtr FreeImage_GetBits(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_Unload@4", SetLastError = true)]private static extern int FreeImage_Free(IntPtr Dib);[DllImport("FreeImage.dll", EntryPoint = "_FreeImage_FlipVertical@4", SetLastError = true)]private static extern int FreeImage_FlipVertical(IntPtr Dib);
接下来就可以调用FreeImage.dll中的函数了，用FreeImage.dll来加载一张图片，代码如下：
Bitmap Bmp = null;FREE_IMAGE_FORMAT fif = FREE_IMAGE_FORMAT.FIF_UNKNOWN; ;fif = FreeImage_GetFileType(FileName, 0);//获取加载图像的格式if (fif == FREE_IMAGE_FORMAT.FIF_UNKNOWN){fif = FreeImage_GetFIFFromFilename(FileName);}if ((fif != FREE_IMAGE_FORMAT.FIF_UNKNOWN) && (FreeImage_FIFSupportsReading(fif) != 0)){IntPtr Dib = FreeImage_Load(fif, FileName, 0); //获取图像数据指针int Bpp = FreeImage_GetBPP(Dib);//获取图像深度PixelFormat PF;int Width, Height, Stride;switch (Bpp){case 1:PF = PixelFormat.Format1bppIndexed; break;case 4:PF = PixelFormat.Format4bppIndexed; break;case 8:PF = PixelFormat.Format8bppIndexed; break;case 16:PF = PixelFormat.Format16bppRgb555; break;case 24:PF = PixelFormat.Format24bppRgb; break;case 32:PF = PixelFormat.Format32bppArgb; break;default:FreeImage_Free(Dib);return null;}Width = FreeImage_GetWidth(Dib); // 图像宽度Height = FreeImage_GetHeight(Dib); // 图像高度Stride = FreeImage_GetPitch(Dib); // 图像扫描行的大小,必然是4的整数倍
如果我们想要将图像数据转为BYTE[]格式，有两种方式：
1.直接用copy函数
int copycount = Width * Height * 4;IntPtr Bits = FreeImage_GetBits(Dib);byte[] line1 = new byte[Width * Height * 4];System.Runtime.InteropServices.Marshal.Copy(Bits, line1, 0, copycount);//copy 图像数据
2.用BitMap中内存操作函数
byte[] line = new byte[Width * Height * 4];byte temp;//32位 RGBA格式图像信息BitmapData bdata = Bmp.LockBits(new Rectangle(0, 0, Bmp.Width, Bmp.Height), ImageLockMode.ReadWrite, PF);{unsafe {byte* ptr = (byte*)(bdata.Scan0);IntPtr ptr1 = bdata.Scan0;System.Runtime.InteropServices.Marshal.Copy(ptr1,line,0,copycount);}}
Bmp.UnlockBits(bdata);
以上就可以实现图像数据的操作了。
