// Encode writes an arbitrary image in any of the Netpbm formats. If opts is
// nil, Encode will default to matching the image format if the image is a
// Netpbm image or producing a raw PPM file with no header comment and a
// maximum color-channel value of 255 for any other image type.
func Encode(w io.Writer, img image.Image, opts *EncodeOptions) error {
var o EncodeOptions
if opts == nil {
// Select some reasonable default options.
switch img := img.(type) {
case Image:
o = EncodeOptions{
Format: img.Format(),
MaxValue: img.MaxValue(),
}
default:
o = EncodeOptions{
Format: PPM,
MaxValue: 255,
}
}
} else {
// Ensure the provided options are sensible.
o = *opts
if o.MaxValue < 0 {
return errors.New("MaxValue must be greater than 0")
}
}
switch o.Format {
case PPM:
return encodePPM(w, img, &o)
case PGM:
return encodePGM(w, img, &o)
case PBM:
return encodePBM(w, img, &o)
default:
return fmt.Errorf("Invalid Netpbm format specified (%s)", o.Format)
}
}