How to preview the part like openfile dialog box with same quality?

I want to preview the part like openfile dialog box befort open the part file.

I used the three methods but the image is not good at pixel or precision,

the image in openfile dialog box is better than that.Look the pictute.

I don't know how to get the image with the same precision .

My code is(in SW2007)

        Me.Image1.Picture = swCfg.GetPreviewBitmap(nRetVal)
        Me.Image2.Picture = swCfg.GetPreviewPNGBitmap(nRetVal)
        Me.Image3.Picture = swApp.GetPreviewBitmap(openFile, vCfgName)

SolidworksApi macros