func hPackedDIBFromHBITMAP(hBmp win.HBITMAP) (win.HGLOBAL, error) {
var dib win.DIBSECTION
if win.GetObject(win.HGDIOBJ(hBmp), unsafe.Sizeof(dib), unsafe.Pointer(&dib)) == 0 {
return 0, newError("GetObject failed")
}
bmihSize := uintptr(unsafe.Sizeof(dib.DsBmih))
pixelsSize := uintptr(
int32(dib.DsBmih.BiBitCount) * dib.DsBmih.BiWidth * dib.DsBmih.BiHeight)
totalSize := bmihSize + pixelsSize
hPackedDIB := win.GlobalAlloc(win.GHND, totalSize)
dest := win.GlobalLock(hPackedDIB)
defer win.GlobalUnlock(hPackedDIB)
src := unsafe.Pointer(&dib.DsBmih)
win.MoveMemory(dest, src, bmihSize)
dest = unsafe.Pointer(uintptr(dest) + bmihSize)
src = unsafe.Pointer(uintptr(src) + bmihSize)
win.MoveMemory(dest, src, pixelsSize)
return hPackedDIB, nil
}
func newBitmapFromHBITMAP(hBmp win.HBITMAP) (bmp *Bitmap, err error) {
var dib win.DIBSECTION
if win.GetObject(win.HGDIOBJ(hBmp), unsafe.Sizeof(dib), unsafe.Pointer(&dib)) == 0 {
return nil, newError("GetObject failed")
}
bmih := &dib.DsBmih
bmihSize := uintptr(unsafe.Sizeof(*bmih))
pixelsSize := uintptr(int32(bmih.BiBitCount)*bmih.BiWidth*bmih.BiHeight) / 8
totalSize := uintptr(bmihSize + pixelsSize)
hPackedDIB := win.GlobalAlloc(win.GHND, totalSize)
dest := win.GlobalLock(hPackedDIB)
defer win.GlobalUnlock(hPackedDIB)
src := unsafe.Pointer(&dib.DsBmih)
win.MoveMemory(dest, src, bmihSize)
dest = unsafe.Pointer(uintptr(dest) + bmihSize)
src = dib.DsBm.BmBits
win.MoveMemory(dest, src, pixelsSize)
return &Bitmap{
hBmp: hBmp,
hPackedDIB: hPackedDIB,
size: Size{
int(bmih.BiWidth),
int(bmih.BiHeight),
},
}, nil
}