encode.go

package goopenjpeg

import (
	"fmt"

	"github.com/godicom-dev/goopenjpeg/native"
)

// Colour spaces matching OpenJPEG OPJ_COLOR_SPACE.
const (
	ColourUnspecified = 0
	ColourSRGB        = 1
	ColourGray        = 2
	ColourSYCC        = 3
	ColourEYCC        = 4
	ColourCMYK        = 5
)

// EncodeOptions configures Encode / EncodePixelData.
type EncodeOptions struct {
	Columns         int
	Rows            int
	SamplesPerPixel int
	BitsStored      int
	IsSigned        bool
	ColourSpace     int
	UseMCT          bool
	Codec           Codec
	// ProgressionOrder applies to HTJ2K encode (.201 LRCP, .202 RPCL).
	ProgressionOrder ProgressionOrder
	// CompressionRatios empty => lossless (DWT 5-3).
	CompressionRatios []float64
}

// Encode encodes little-endian colour-by-pixel samples to JPEG 2000.
func Encode(src []byte, opts EncodeOptions) ([]byte, error) {
	if opts.Codec == 0 {
		opts.Codec = CodecJ2K
	}
	if opts.ColourSpace == 0 && opts.SamplesPerPixel == 1 {
		opts.ColourSpace = ColourGray
	}
	if opts.ColourSpace == 0 && opts.SamplesPerPixel == 3 {
		opts.ColourSpace = ColourSRGB
	}
	return native.Encode(src, native.EncodeOptions{
		Columns:           opts.Columns,
		Rows:              opts.Rows,
		SamplesPerPixel:   opts.SamplesPerPixel,
		BitsStored:        opts.BitsStored,
		IsSigned:          opts.IsSigned,
		ColourSpace:       opts.ColourSpace,
		UseMCT:            opts.UseMCT,
		Codec:             int(opts.Codec),
		ProgressionOrder:  int(opts.ProgressionOrder),
		CompressionRatios: opts.CompressionRatios,
	})
}

// EncodePixelData encodes a single DICOM frame for JPEG 2000 transfer syntaxes.
func EncodePixelData(src []byte, opts PixelDataOptions, frame EncodeOptions) ([]byte, error) {
	if opts.Codec != 0 {
		frame.Codec = opts.Codec
	}
	if frame.Codec == 0 {
		frame.Codec = CodecJ2K
	}
	if frame.ColourSpace == 0 {
		switch opts.PhotometricInterpretation {
		case "MONOCHROME1", "MONOCHROME2":
			frame.ColourSpace = ColourGray
		case "RGB":
			frame.ColourSpace = ColourSRGB
			frame.UseMCT = true
		case "YBR_FULL", "YBR_ICT", "YBR_RCT":
			frame.ColourSpace = ColourSYCC
		}
	}
	out, err := Encode(src, frame)
	if err != nil {
		return nil, fmt.Errorf("goopenjpeg: encode pixel data: %w", err)
	}
	return out, nil
}