fix jpeg

Overlord-Client/cmd/agent/capture/jpeg_turbo.go

@@ -5,18 +5,19 @@ package capture
 import (
 	"bytes"
 	"image"
+	"image/color"
 
 	ljpeg "github.com/pixiv/go-libjpeg/jpeg"
 )
 
 func encodeJPEG(img image.Image, quality int) ([]byte, error) {
 	opts := &ljpeg.EncoderOptions{
-		Quality:        quality,
+		Quality:        jpegEncoderQuality(quality),
 		OptimizeCoding: true,
 		DCTMethod:      ljpeg.DCTISlow,
 	}
 	buf := bytes.Buffer{}
-	if err := ljpeg.Encode(&buf, img, opts); err != nil {
+	if err := ljpeg.Encode(&buf, jpeg444Image(img), opts); err != nil {
 		return nil, err
 	}
 	return buf.Bytes(), nil
@@ -24,9 +25,49 @@ func encodeJPEG(img image.Image, quality int) ([]byte, error) {
 
 func encodeJPEGToBuf(dst *bytes.Buffer, img image.Image, quality int) error {
 	opts := &ljpeg.EncoderOptions{
-		Quality:        quality,
+		Quality:        jpegEncoderQuality(quality),
 		OptimizeCoding: true,
 		DCTMethod:      ljpeg.DCTISlow,
 	}
-	return ljpeg.Encode(dst, img, opts)
+	return ljpeg.Encode(dst, jpeg444Image(img), opts)
+}
+
+// libjpeg preserves the source YCbCr sampling factors, unlike Go's standard
+// JPEG encoder, so TurboJPEG builds can retain full chroma resolution.
+func jpeg444Image(src image.Image) image.Image {
+	if src == nil {
+		return src
+	}
+	if ycbcr, ok := src.(*image.YCbCr); ok && ycbcr.SubsampleRatio == image.YCbCrSubsampleRatio444 {
+		return src
+	}
+
+	bounds := src.Bounds()
+	dst := image.NewYCbCr(bounds, image.YCbCrSubsampleRatio444)
+	if rgba, ok := src.(*image.RGBA); ok {
+		for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+			srcOffset := rgba.PixOffset(bounds.Min.X, y)
+			dstOffset := dst.YOffset(bounds.Min.X, y)
+			for x := 0; x < bounds.Dx(); x++ {
+				i := srcOffset + x*4
+				yy, cb, cr := color.RGBToYCbCr(rgba.Pix[i], rgba.Pix[i+1], rgba.Pix[i+2])
+				dst.Y[dstOffset+x] = yy
+				dst.Cb[dstOffset+x] = cb
+				dst.Cr[dstOffset+x] = cr
+			}
+		}
+		return dst
+	}
+
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			pixel := color.NRGBAModel.Convert(src.At(x, y)).(color.NRGBA)
+			yy, cb, cr := color.RGBToYCbCr(pixel.R, pixel.G, pixel.B)
+			offset := dst.YOffset(x, y)
+			dst.Y[offset] = yy
+			dst.Cb[offset] = cb
+			dst.Cr[offset] = cr
+		}
+	}
+	return dst
 }