how to used VG_BW_1 ?

i used TI OMAP3530.
//PATTERN image
VGubyte cimagedata[4*32]={0xff…};

VGImage image = vgCreateImage( VG_BW_1, 32, 32, VG_IMAGE_QUALITY_BETTER );
vgImageSubData( image, cimagedata, 4, VG_BW_1, 0, 0, 32, 32 );

vgFillPaint = vgCreatePaint();
vgPaintPattern ( vgFillPaint, image );
vgSetParameteri( vgFillPaint, VG_PAINT_TYPE, VG_PAINT_TYPE_PATTERN );
vgSetParameteri( vgFillPaint, VG_PAINT_PATTERN_TILING_MODE, VG_TILE_REPEAT );

“VG_BW_1” Display images appear migration.

//GRAY image
VGubyte cimagedata[32*32]={0xff…};

VGImage image = vgCreateImage( VG_A_8, 32, 32, VG_IMAGE_QUALITY_BETTER );
vgImageSubData( image, cimagedata, 32, VG_A_8, 0, 0, 32, 32 );

“VG_A_8” or “VG_sL_8” or “VG_sL_8” Display images normal

how to used VG_BW_1 ?
thanks.