使用gamma校正提升jpg亮度

pkg/producer/jpg.go

@@ -0,0 +1,150 @@
+package imageproc
+
+import (
+	"fmt"
+	"image"
+	"math"
+
+	"github.com/airbusgeo/godal"
+	log "github.com/sirupsen/logrus"
+	"gocv.io/x/gocv"
+)
+
+func GTiffToJPG(ftiff, fjpg string, reversed bool) error {
+	// 打开 TIFF 文件
+	ds, err := godal.Open(ftiff)
+	if err != nil {
+		log.Printf("Error opening TIFF file %s: %v", ftiff, err)
+		return err
+	}
+	defer ds.Close()
+
+	bands := ds.Bands()
+	log.Infof("creating JPG for TIFF file %s.", ftiff)
+
+	// 获取图像大小
+	width := bands[0].Structure().SizeX
+	height := bands[0].Structure().SizeY
+	bandsCnt := len(bands)
+
+	// 创建 16 位图像矩阵
+	var img gocv.Mat
+	defer img.Close()
+	if bandsCnt == 1 {
+		img = gocv.NewMatWithSize(height, width, gocv.MatTypeCV16UC1)
+	} else {
+		bandsCnt = 3 // 只取前三个波段
+		img = gocv.NewMatWithSize(height, width, gocv.MatTypeCV16UC3)
+	}
+
+	// 读取每个波段并存储到图像矩阵中
+	for i := 0; i < bandsCnt; i++ {
+		band := bands[i]
+		data := make([]uint16, width*height)
+		err = band.Read(0, 0, data, width, height)
+		if err != nil {
+			fmt.Printf("Error reading band %d: %v\n", i, err)
+			return err
+		}
+
+		// 将 16 位数据存储到图像的相应通道
+		for y := 0; y < height; y++ {
+			for x := 0; x < width; x++ {
+				value := data[y*width+x]
+				img.SetShortAt(y, x*bandsCnt+i, int16(value))
+			}
+		}
+	}
+
+	channels := gocv.Split(img)
+	for i, ch := range channels {
+		// 2. 计算图像的最小值和最大值
+		minVal, maxVal, minLoc, maxLoc := gocv.MinMaxLoc(ch)
+		log.Printf("Min value: %f, Max value: %f, min location: %v, max location: %v", minVal, maxVal, minLoc, maxLoc)
+
+		// 3. 将16位图像线性拉伸到8位图像
+		scale := 255.0 / (maxVal - minVal)
+		shift := -minVal * scale
+		ch.ConvertToWithParams(&channels[i], gocv.MatTypeCV8U, scale, shift)
+	}
+
+	img8bit := gocv.NewMat()
+	defer img8bit.Close()
+	if reversed {
+		gocv.Merge([]gocv.Mat{channels[2], channels[1], channels[0]}, &img8bit)
+	} else {
+		gocv.Merge(channels, &img8bit)
+	}
+
+	for i := range channels {
+		channels[i].Close()
+	}
+
+	gocv.Resize(img8bit, &img8bit,
+		image.Point{X: img8bit.Cols() / 2, Y: img8bit.Rows() / 2},
+		0, 0, gocv.InterpolationCubic)
+
+	// 7. 应用伽玛校正提升亮度
+	// avgBrightness := calculateAverageBrightness(img8bit)
+	// gamma := determineGammaValue(avgBrightness)
+	// log.Printf("Average Brightness: %f, Determined Gamma: %f", avgBrightness, gamma)
+
+	gammaCorrected := applyGammaCorrection(img8bit, 1.6) // 伽玛值
+	defer gammaCorrected.Close()
+	ok := gocv.IMWriteWithParams(fjpg, gammaCorrected, []int{gocv.IMWriteJpegOptimize, 1})
+	if !ok {
+		err = fmt.Errorf("error saving %s", fjpg)
+		return err
+	}
+
+	// gocv.IMWrite(strings.Replace(fjpg, ".jpg", "_8.jpg", 1), img8bit)
+
+	return nil
+}
+
+// applyGammaCorrection applies gamma correction to the image
+func applyGammaCorrection(src gocv.Mat, gamma float64) gocv.Mat {
+	lookupTable := make([]uint8, 256)
+	invGamma := 1.0 / gamma
+	for i := 0; i < 256; i++ {
+		lookupTable[i] = uint8(math.Pow(float64(i)/255.0, invGamma) * 255.0)
+	}
+
+	dst := gocv.NewMat()
+	gammaMat, err := gocv.NewMatFromBytes(1, 256, gocv.MatTypeCV8UC1, lookupTable)
+	if err != nil {
+		log.Printf("Error creating gamma correction matrix: %v", err)
+		return src
+	}
+	defer gammaMat.Close()
+
+	gocv.LUT(src, gammaMat, &dst)
+	return dst
+}
+
+// calculateAverageBrightness calculates the average brightness of the image
+func calculateAverageBrightness(img gocv.Mat) float64 {
+	if img.Channels() == 1 {
+		return img.Mean().Val1
+	}
+	gray := gocv.NewMat()
+	defer gray.Close()
+	gocv.CvtColor(img, &gray, gocv.ColorBGRToGray)
+	return gray.Mean().Val1
+	// mean := gocv.NewMat()
+	// dstStdDev := gocv.NewMat()
+	// defer mean.Close()
+	// defer dstStdDev.Close()
+	// gocv.MeanStdDev(gray, &mean, &dstStdDev)
+	// return float64(mean.GetFloatAt(0, 0))
+}
+
+// determineGammaValue determines an appropriate gamma value based on the average brightness
+func determineGammaValue(avgBrightness float64) float64 {
+	targetBrightness := 180.0
+	if avgBrightness < 0.1 {
+		return 1.0
+	}
+	gamma := math.Log(targetBrightness/255.0) / math.Log(avgBrightness/255.0)
+	return gamma
+}