DirectX与VB.NET编程（十五）*色深理论与图片智能加载

Dim vSecondarySurface As Surface
Dim vSecondarySurfaceCaps As New SurfaceCaps
Dim vSecondarySurfaceDesc As SurfaceDescriptionDirectX与VB.NET编程（十五）*色深理论与图片智能加载

'取得图片大小
Dim vBitmap As New Bitmap(OpenFileDialog1.FileName)
Dim vSize As Integer = vBitmap.Width * vBitmap.Height * Convert(vBitmap.PixelFormat)

'取得剩余显存空间
Dim vVideoFree As Integer = vDevice.HardwareCaps.VideoMemoryFree

'比较显存是否足够
If vVideoFree > vSize Then
    '显存足够，使用显存进行存放
    MsgBox("显存空间足够，剩余显存：" + vVideoFree.ToString + " 图片大小：" + vSize.ToString)
    vSecondarySurfaceCaps.VideoMemory = True
Else
    '显存不足，使用内存进行存放
    MsgBox("显存空间不足，剩余显存：" + vVideoFree.ToString + " 图片大小：" + vSize.ToString)
    vSecondarySurfaceCaps.SystemMemory = True
End If

'初始化表面、加载图片并显示剩余显存
vSecondarySurfaceCaps.OffScreenPlain = True
vSecondarySurfaceDesc = New SurfaceDescription(vSecondarySurfaceCaps)
vSecondarySurface = New Surface(OpenFileDialog1.FileName, vSecondarySurfaceDesc, vDevice)
vVideoFree = vDevice.HardwareCaps.VideoMemoryFree
MsgBox("图片已加载，剩余显存：" + vVideoFree.ToString)

此外需要注意的是，Bitmap的PixelFormat属性取到的只是一些枚举，因此我们自己写一个函数需要将其转化为Integer类型：
Private Function Convert(ByVal EnumType As Drawing.Imaging.PixelFormat) As Integer
    Select Case EnumType
        Case Imaging.PixelFormat.Format16bppArgb1555
            Return 16DirectX与VB.NET编程（十五）*色深理论与图片智能加载
        Case Imaging.PixelFormat.Format16bppGrayScale
            Return 16
        Case Imaging.PixelFormat.Format16bppRgb555
            Return 16
        Case Imaging.PixelFormat.Format1bppIndexed
            Return 1
        Case Imaging.PixelFormat.Format24bppRgb
            Return 24
        Case Imaging.PixelFormat.Format32bppArgb
            Return 32
        Case Imaging.PixelFormat.Format32bppPArgb
            Return 32
        Case Imaging.PixelFormat.Format32bppRgb
            Return 32
        Case Imaging.PixelFormat.Format48bppRgb
            Return 48
        Case Imaging.PixelFormat.Format4bppIndexed
            Return 4
        Case Imaging.PixelFormat.Format64bppArgb
            Return 64
        Case Imaging.PixelFormat.Format64bppPArgb
            Return 64
        Case Imaging.PixelFormat.Format8bppIndexed
            Return 8
        Case Else
            Return 1DirectX与VB.NET编程（十五）*色深理论与图片智能加载
    End Select
End Function