var ex C.ExceptionInfo

C.GetExceptionInfo(&ex)

defer C.DestroyExceptionInfo(&ex)

var colors C.ulong

hist := C.GetColorHistogram(im.image, &colors, &ex)

if hist == nil {

return nil, exError(&ex, "getting histogram")

}

defer C.free(unsafe.Pointer(hist))

count := int(colors)

items := make([]*HistogramItem, count)

var hitems []C.HistogramColorPacket

sliceHeader := (*reflect.SliceHeader)((unsafe.Pointer(&hitems)))

sliceHeader.Cap = count

sliceHeader.Len = count

sliceHeader.Data = uintptr(unsafe.Pointer(hist))

for ii, v := range hitems {

px := newPixel(&v.pixel)

items[ii] = &HistogramItem{px, int(v.count)}

}

return &Histogram{items}, nil