C#编程->FreeImage.dll使用方法

       

         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。