2023-03-10：YUV420P像素数据编码为JPEG图片，请用go语言实现。

2023-03-10：YUV420P像素数据编码为JPEG图片，请用go语言实现。

答案2023-03-10：

方法一、使用 github.com/moonfdd/ffmpeg-go 库,基于雷霄骅的代码修改。

方法二、使用golang官方库image/jpeg，yuv420p先转换成rgb，再转换成jpeg。代码是用山寨版的chatgpt生成。

go run ./examples/leixiaohua1020/simplest_ffmpeg_picture_encoder/main.go

方法一，参考了雷霄骅的图像编码器，代码用golang编写。代码如下：

// https://github.com/leixiaohua1020/simplest_ffmpeg_picture_encoder/blob/master/simplest_ffmpeg_picture_encoder/simplest_ffmpeg_picture_encoder.cpp
package main

import (
	"fmt"
	"os"
	"os/exec"
	"unsafe"

	"github.com/moonfdd/ffmpeg-go/ffcommon"
	"github.com/moonfdd/ffmpeg-go/libavcodec"
	"github.com/moonfdd/ffmpeg-go/libavformat"
	"github.com/moonfdd/ffmpeg-go/libavutil"
)

func main0() (ret ffcommon.FInt) {
	var pFormatCtx *libavformat.AVFormatContext
	var fmt0 *libavformat.AVOutputFormat
	var video_st *libavformat.AVStream
	var pCodecCtx *libavcodec.AVCodecContext
	var pCodec *libavcodec.AVCodec

	var picture_buf *ffcommon.FUint8T
	var picture *libavutil.AVFrame
	var pkt libavcodec.AVPacket
	var y_size ffcommon.FInt
	var got_picture ffcommon.FInt = 0
	var size ffcommon.FInt

	var in_file *os.File                    //YUV source
	var in_w, in_h ffcommon.FInt = 640, 360 //YUV's width and height
	var out_file = "./out/pic.jpg"          //Output file
	in := "./out/pic.yuv"

	//是否存在yuv文件
	_, err := os.Stat(in)
	if err != nil {
		if os.IsNotExist(err) {
			fmt.Println("create yuv file")
			exec.Command("./lib/ffmpeg", "-i", "./resources/big_buck_bunny.mp4", "-pix_fmt", "yuv420p", in, "-y").CombinedOutput()
		}
	}

	in_file, _ = os.Open(in)
	if in_file == nil {
		return -1
	}

	libavformat.AvRegisterAll()

	//Method 1
	pFormatCtx = libavformat.AvformatAllocContext()
	//Guess format
	fmt0 = libavformat.AvGuessFormat("mjpeg", "", "")
	pFormatCtx.Oformat = fmt0
	//Output URL
	if libavformat.AvioOpen(&pFormatCtx.Pb, out_file, libavformat.AVIO_FLAG_READ_WRITE) < 0 {
		fmt.Printf("Couldn't open output file.")
		return -1
	}

	//Method 2. More simple
	//avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);
	//fmt = pFormatCtx->oformat;

	video_st = pFormatCtx.AvformatNewStream(nil)
	if video_st == nil {
		return -1
	}
	pCodecCtx = video_st.Codec
	pCodecCtx.CodecId = fmt0.VideoCodec
	pCodecCtx.CodecType = libavutil.AVMEDIA_TYPE_VIDEO
	pCodecCtx.PixFmt = libavutil.AV_PIX_FMT_YUVJ420P

	pCodecCtx.Width = in_w
	pCodecCtx.Height = in_h

	pCodecCtx.TimeBase.Num = 1
	pCodecCtx.TimeBase.Den = 25
	//Output some information
	pFormatCtx.AvDumpFormat(0, out_file, 1)

	pCodec = libavcodec.AvcodecFindEncoder(pCodecCtx.CodecId)
	if pCodec == nil {
		fmt.Printf("Codec not found.")
		return -1
	}
	if pCodecCtx.AvcodecOpen2(pCodec, nil) < 0 {
		fmt.Printf("Could not open codec.")
		return -1
	}
	picture = libavutil.AvFrameAlloc()
	picture.Width = pCodecCtx.Width
	picture.Height = pCodecCtx.Height
	picture.Format = pCodecCtx.PixFmt
	size = libavcodec.AvpictureGetSize(pCodecCtx.PixFmt, pCodecCtx.Width, pCodecCtx.Height)
	picture_buf = (*byte)(unsafe.Pointer(libavutil.AvMalloc(uint64(size))))
	if picture_buf == nil {
		return -1
	}
	((*libavcodec.AVPicture)(unsafe.Pointer(picture))).AvpictureFill(picture_buf, pCodecCtx.PixFmt, pCodecCtx.Width, pCodecCtx.Height)

	//Write Header
	pFormatCtx.AvformatWriteHeader(nil)

	y_size = pCodecCtx.Width * pCodecCtx.Height
	pkt.AvNewPacket(y_size * 3)
	//Read YUV
	_, err = in_file.Read(ffcommon.ByteSliceFromByteP(picture_buf, int(y_size*3/2)))
	if err != nil {
		fmt.Printf("Could not read input file.%s", err)
		return -1
	}
	picture.Data[0] = picture_buf                                                                         // Y
	picture.Data[1] = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(picture_buf)) + uintptr(y_size)))     // U
	picture.Data[2] = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(picture_buf)) + uintptr(y_size*5/4))) // V

	//Encode
	ret = pCodecCtx.AvcodecEncodeVideo2(&pkt, picture, &got_picture)
	if ret < 0 {
		fmt.Printf("Encode Error.\n")
		return -1
	}
	if got_picture == 1 {
		pkt.StreamIndex = uint32(video_st.Index)
		ret = pFormatCtx.AvWriteFrame(&pkt)
	}

	pkt.AvFreePacket()
	//Write Trailer
	pFormatCtx.AvWriteTrailer()

	fmt.Printf("Encode Successful.\n")

	if video_st != nil {
		video_st.Codec.AvcodecClose()
		libavutil.AvFree(uintptr(unsafe.Pointer(picture)))
		libavutil.AvFree(uintptr(unsafe.Pointer(picture_buf)))
	}
	pFormatCtx.Pb.AvioClose()
	pFormatCtx.AvformatFreeContext()

	in_file.Close()

	exec.Command("./lib/ffplay.exe", out_file).Output()
	if err != nil {
		fmt.Println("play err = ", err)
	}

	return 0
}

func main() {

	os.Setenv("Path", os.Getenv("Path")+";./lib")
	ffcommon.SetAvutilPath("./lib/avutil-56.dll")
	ffcommon.SetAvcodecPath("./lib/avcodec-58.dll")
	ffcommon.SetAvdevicePath("./lib/avdevice-58.dll")
	ffcommon.SetAvfilterPath("./lib/avfilter-56.dll")
	ffcommon.SetAvformatPath("./lib/avformat-58.dll")
	ffcommon.SetAvpostprocPath("./lib/postproc-55.dll")
	ffcommon.SetAvswresamplePath("./lib/swresample-3.dll")
	ffcommon.SetAvswscalePath("./lib/swscale-5.dll")

	genDir := "./out"
	_, err := os.Stat(genDir)
	if err != nil {
		if os.IsNotExist(err) {
			os.Mkdir(genDir, 0777) //  Everyone can read write and execute
		}
	}

	// go func() {
	// 	time.Sleep(1000)
	// 	exec.Command("./lib/ffplay.exe", "rtmp://localhost/publishlive/livestream").Output()
	// 	if err != nil {
	// 		fmt.Println("play err = ", err)
	// 	}
	// }()

	main0()
}

方法二，用第1个chatgpt生成golang代码：

// https://chat.forchange.cn/
// YUV420P像素数据编码为JPEG图片，请用go语言实现。

package main

import (
	"bufio"
	"fmt"
	"image"
	"image/color"
	"image/jpeg"
	"os"
)

func main() {
	// 将YUV420P像素数据读入内存
	yuvFile, err := os.Open("./out/pic.yuv")
	if err != nil {
		fmt.Println(err)
		return
	}
	defer yuvFile.Close()
	width := 640
	height := 360
	yuvData := make([]byte, width*height*3/2)
	yuvReader := bufio.NewReader(yuvFile)
	_, err = yuvReader.Read(yuvData)
	if err != nil {
		fmt.Println(err)
		return
	}
	// 将YUV420P像素数据转换为RGB格式的图像
	img := image.NewRGBA(image.Rect(0, 0, width, height))
	for y2 := 0; y2 < height; y2++ {
		for x := 0; x < width; x++ {
			// 从YUV420P像素数据中获取Y、U、V值
			yIndex := y2*width + x
			uIndex := width*height + (y2/2)*(width/2) + x/2
			vIndex := width*height*5/4 + (y2/2)*(width/2) + x/2
			y3 := float64(yuvData[yIndex])
			u := float64(yuvData[uIndex]) - 128.0
			v := float64(yuvData[vIndex]) - 128.0
			// 将YUV值转换为RGB值
			r := y3 + 1.402*v
			g := y3 - 0.344*u - 0.714*v
			b := y3 + 1.772*u
			// 将RGB值限制在0-255范围内
			r = limit(r, 0, 255)
			g = limit(g, 0, 255)
			b = limit(b, 0, 255)
			// 将RGB值保存到图像中
			img.Set(x, y2, color.RGBA{uint8(r), uint8(g), uint8(b), 255})
		}
	}
	// 将图像编码为JPEG图片并保存到文件中
	jpegFile, err := os.Create("./out/pic2.jpg")
	if err != nil {
		fmt.Println(err)
		return
	}
	defer jpegFile.Close()
	err = jpeg.Encode(jpegFile, img, nil)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("JPEG image saved to ./out/pic2.jpg")
}

// 将value限制在min和max之间
func limit(value, min, max float64) float64 {
	if value < min {
		return min
	}
	if value > max {
		return max
	}
	return value
}

方法二，用第2个chatgpt生成golang代码：

// https://chatgpt.zcorky.com/ 第一次失败，第二次成功
// YUV420P像素数据编码为JPEG图片，请用go语言实现。不要用第三方库
package main

import (
	"bufio"
	"bytes"
	"fmt"
	"image"
	"image/color"
	"image/jpeg"
	"os"
)

func main() {
	// 将YUV420P像素数据读入内存
	yuvFile, err := os.Open("./out/pic.yuv")
	if err != nil {
		fmt.Println(err)
		return
	}
	defer yuvFile.Close()
	width := 640
	height := 360
	yuvData := make([]byte, width*height*3/2)
	yuvReader := bufio.NewReader(yuvFile)
	_, err = yuvReader.Read(yuvData)
	if err != nil {
		fmt.Println(err)
		return
	}

	// 假设您已经读取了 YUV420P 格式的像素数据，并将其存储在 data 变量中
	var yuv []byte = yuvData // YUV420P 数据

	// 创建一个新的 RGBA 图像
	rgbaImg := image.NewRGBA(image.Rect(0, 0, width, height))

	// 将 YUV420P 数据转换为 RGBA 数据
	for i := 0; i < width*height; i++ {
		yi := int(yuv[i])
		ui := int(yuv[width*height+(i/4)])
		vi := int(yuv[width*height+(width*height/4)+(i/4)])

		r := float64(yi) + 1.4065*(float64(vi)-128)
		g := float64(yi) - 0.3455*(float64(ui)-128) - 0.7169*(float64(vi)-128)
		b := float64(yi) + 1.7790*(float64(ui)-128)

		if r < 0 {
			r = 0
		} else if r > 255 {
			r = 255
		}

		if g < 0 {
			g = 0
		} else if g > 255 {
			g = 255
		}

		if b < 0 {
			b = 0
		} else if b > 255 {
			b = 255
		}

		rgbaImg.SetRGBA(i%width, i/width, color.RGBA{
			R: uint8(r),
			G: uint8(g),
			B: uint8(b),
			A: 255,
		})
	}

	// 创建 JPEG 图像文件
	jpgFile, err := os.Create("./out/pic3.jpg")
	if err != nil {
		panic(err)
	}
	defer jpgFile.Close()

	// 使用 image/jpeg 包来编码 JPEG 图像
	buf := new(bytes.Buffer)
	if err := jpeg.Encode(buf, rgbaImg, &jpeg.Options{Quality: 80}); err != nil {
		panic(err)
	}

	_, err = jpgFile.Write(buf.Bytes())
	if err != nil {
		panic(err)
	}
}