Smily not look transparent in CEikRichTextEditor

Hi All,
I have add picture in CEikRichTextEditor using code:

CWindowGc& gc = SystemGc();

CRTxPicture* picture;
picture = new(ELeave) CRTxPicture(gc, aControl, aBitmap, aBitmapMask);
CleanupStack::PushL(picture);

TPictureHeader header;

header.iPicture = TSwizzle(picture);
header.iPictureType.iUid=aSmiUid;

iRtEd->RichText()->InsertL(aPos, header);

picture(smily) shows properly but it does not look transparent(background of smily looks black ) .