decode_logluv.go

package tiff

import (
	"image"

	"github.com/mdouchement/hdr"
	"github.com/mdouchement/hdr/format"
	"github.com/mdouchement/hdr/hdrcolor"
)

func (d *decoder) decodeLogLuv(dst image.Image, xmin, ymin, xmax, ymax int) error {
	// Apply horizontal predictor if necessary.
	// In this case, p contains the color difference to the preceding pixel.
	// See page 64-65 of the spec.
	if d.firstVal(tPredictor) > prNone {
		return UnsupportedError("predictor")
	}

	rMaxX := minInt(xmax, dst.Bounds().Max.X)
	rMaxY := minInt(ymax, dst.Bounds().Max.Y)
	var offset uint

	stonits := d.features[tStonits].double(0)
	if stonits == 0 {
		stonits = 1
	}

	m := dst.(*hdr.XYZ)
	for y := ymin; y < rMaxY; y++ {
		for x := xmin; x < rMaxX; x++ {
			X, Y, Z := format.LogLuvToXYZ(d.buf[offset], d.buf[offset+1], d.buf[offset+2], d.buf[offset+3])
			m.SetXYZ(x, y, hdrcolor.XYZ{X: X * stonits, Y: Y * stonits, Z: Z * stonits})
			offset += 4 // LogLuv is hold on 4 bytes
		}
	}

	return nil
}