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fits.go
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fits.go
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package camera
import (
"image"
"io"
"reflect"
"unsafe"
"github.com/astrogo/fitsio"
)
// WriteFits streams a fits file to w
func WriteFits(w io.Writer, metadata []fitsio.Card, imgs []image.Image) error {
metadata = append(metadata, fitsio.Card{Name: "BZERO", Value: 32768}, fitsio.Card{Name: "BSCALE", Value: 1.0})
nframes := len(imgs)
b := imgs[0].Bounds()
width, height := b.Dx(), b.Dy()
fits, err := fitsio.Create(w)
if err != nil {
return err
}
defer fits.Close()
dims := []int{width, height}
if nframes > 1 {
dims = append(dims, nframes)
}
im := fitsio.NewImage(16, dims)
defer im.Close()
err = im.Header().Append(metadata...)
if err != nil {
return err
}
bufSize := 1
for _, s := range dims {
bufSize *= s
}
ints := make([]int16, bufSize)
offset := 0
for _, img := range imgs {
imgConcrete := (img).(*image.Gray16)
uints := bytesToUint(imgConcrete.Pix)
l := len(uints)
for idx := 0; idx < l; idx++ {
ints[offset+idx] = int16(uints[idx] - 32768)
}
offset += l
}
err = im.Write(ints)
if err != nil {
return err
}
return fits.Write(im)
}
func bytesToUint(b []byte) []uint16 {
var ary []uint16
hdr := (*reflect.SliceHeader)(unsafe.Pointer(&ary))
hdr.Data = uintptr(unsafe.Pointer(&b[0]))
hdr.Len = len(b) / 2
hdr.Cap = cap(b) / 2
return ary
}