我想知道这两者之间的区别：
Bitmap bitmap1 = new Bitmap("C:\\test.bmp");
Bitmap bitmap2 = (Bitmap) Bitmap.FromFile("C:\\test.bmp");
一种选择比另一种更好吗？ Bitmap.FromFile(path)是否会向位图图像填充任何其他数据,或者它只是新Bitmap(路径)的委托？
解决方法
两种方法都通过path参数获取图像句柄. Image.FromFile将返回超类Image,而前者只返回Bitmap,因此您可以避免强制转换.
在内部,他们几乎都这样做：
public static Image FromFile(String filename,bool useEmbeddedColorManagement)
{
if (!File.Exists(filename))
{
IntSecurity.DemandReadFileIO(filename);
throw new FileNotFoundException(filename);
}
filename = Path.GetFullPath(filename);
IntPtr image = IntPtr.Zero;
int status;
if (useEmbeddedColorManagement)
{
status = SafeNativeMethods.Gdip.GdipLoadImageFromFileICM(filename,out image);
}
else
{
status = SafeNativeMethods.Gdip.GdipLoadImageFromFile(filename,out image);
}
if (status != SafeNativeMethods.Gdip.Ok)
throw SafeNativeMethods.Gdip.StatusException(status);
status = SafeNativeMethods.Gdip.GdipImageForceValidation(new HandleRef(null,image));
if (status != SafeNativeMethods.Gdip.Ok)
{
SafeNativeMethods.Gdip.GdipDisposeImage(new HandleRef(null,image));
throw SafeNativeMethods.Gdip.StatusException(status);
}
Image img = CreateImageObject(image);
EnsureSave(img,filename,null);
return img;
}
和：
public Bitmap(String filename)
{
IntSecurity.DemandReadFileIO(filename);
filename = Path.GetFullPath(filename);
IntPtr bitmap = IntPtr.Zero;
int status = SafeNativeMethods.Gdip.GdipCreateBitmapFromFile(filename,out bitmap);
if (status != SafeNativeMethods.Gdip.Ok)
throw SafeNativeMethods.Gdip.StatusException(status);
status = SafeNativeMethods.Gdip.GdipImageForceValidation(new HandleRef(null,bitmap));
if (status != SafeNativeMethods.Gdip.Ok)
{
SafeNativeMethods.Gdip.GdipDisposeImage(new HandleRef(null,bitmap));
throw SafeNativeMethods.Gdip.StatusException(status);
}
SetNativeImage(bitmap);
EnsureSave(this,null);
}
