.net|.net 通过 WebAPI 调用nsfwjs 进行视频鉴别功能 .net通过WebAPI调用nsfwjs进行视频

1. npm 安装 nsfwjs

npm install express --savenpm install multer --savenpm install jpeg-js --savenpm install @tensorflow/tfjs-node --savenpm install nsfwjs --save

注意:安装 @tensorflow/tfjs-node 需要用到 python, 建议添加到用户环境变量 Path 中
2. 运行 WebAPI 服务 nsfwjs 作者提供了一个简单的 server.js 来提供 WebAPI 服务，为方便复制到这里

const express = require('express')const multer = require('multer')const jpeg = require('jpeg-js')const tf = require('@tensorflow/tfjs-node')const nsfw = require('nsfwjs')const app = express()const upload = multer()let _modelconst convert = async (img) => {// Decoded image in UInt8 Byte arrayconst image = await jpeg.decode(img, true)const numChannels = 3const numPixels = image.width * image.heightconst values = new Int32Array(numPixels * numChannels)for (let i = 0; i < numPixels; i++)for (let c = 0; c < numChannels; ++c)values[i * numChannels + c] = image.data[i * 4 + c]return tf.tensor3d(values, [image.height, image.width, numChannels], 'int32')}app.post('/nsfw', upload.single('image'), async (req, res) => {if (!req.file) res.status(400).send('Missing image multipart/form-data')else {const image = await convert(req.file.buffer)const predictions = await _model.classify(image)image.dispose()res.json(predictions)}})const load_model = async () => {_model = await nsfw.load() //you can specify module here}// Keep the model in memory, make sure it's loaded only onceload_model().then(() => app.listen(8080))

【.net|.net 通过 WebAPI 调用nsfwjs 进行视频鉴别功能】尝试运行这个服务 ( 注意这个app仅支持jpeg格式的图片 )

node server.js

用 curl 测试

curl --request POST localhost:8080/nsfw --header 'Content-Type: multipart/form-data' --data-binary 'image=@myimg.jpg'

想简单些，可以写成这样

curl -F "image=@myimg.jpg" "http://localhost:8080/nsfw"

Windows 下可以通过 Postman 来测试。
3. .net 封装调用 nsfwjs 的 WebAPI 服务能跑起来了，用 .net 封装调用就很简单了
3.1 首先通过 process 启动 node server.js，可以通过输出重定向隐藏控制台
3.2 通过 HttpClient 或者RestSharp 等客户端组件提交需要鉴别的图片，返回结果
3.3 想要分析视频，还可以参考下这篇文章：FFMPEG获取视频关键帧并保存成jpg图像(ps：文末介绍)。
通过调用 ffmpeg 或者使用 FFMpeg.AutoGen 编程实现截图
运行效果上来看还是不错的，200K 以内的图片一般都能在 200ms 内返回鉴别结果。
ps：下面看下FFMPEG获取视频关键帧并保存成jpg图像
1、命令行方式
1秒取1帧 r:rate

ffmpeg -i input.mp4 -f image2 -r 1dstPath/image-%03d.jpg

提取I帧

ffmpeg -i input.mp4 -an -vf select='eq(pict_type\,I)' -vsync 2 -s 720*480 -f image2dstPath/image-%03d.jpg

2、代码方式
提取I帧

//source: keyframe.cpp#include #include #include #define __STDC_CONSTANT_MACROSextern "C"{#include #include #include #include #include #include #include #include #include #include #include #include #include #include }using namespace std; char errbuf[256]; char timebuf[256]; static AVFormatContext *fmt_ctx = NULL; static AVCodecContext *video_dec_ctx = NULL; static int width, height; static enum AVPixelFormat pix_fmt; static AVStream *video_stream = NULL; static const char *src_filename = NULL; static const char *output_dir = NULL; static int video_stream_idx = -1; static AVFrame *frame = NULL; static AVFrame *pFrameRGB = NULL; static AVPacket pkt; static struct SwsContext *pSWSCtx = NULL; static int video_frame_count = 0; /* Enable or disable frame reference counting. You are not supposed to support * both paths in your application but pick the one most appropriate to your * needs. Look for the use of refcount in this example to see what are the * differences of API usage between them. */static int refcount = 0; static void jpg_save(uint8_t *pRGBBuffer, int iFrame, int width, int height); static int decode_packet(int *got_frame, int cached){int ret = 0; int decoded = pkt.size; *got_frame = 0; if (pkt.stream_index == video_stream_idx){/* decode video frame */ret = avcodec_decode_video2(video_dec_ctx, frame, got_frame, &pkt); if (ret < 0){fprintf(stderr, "Error decoding video frame (%s)\n", av_make_error_string(errbuf, sizeof(errbuf), ret)); return ret; }if (*got_frame){if (frame->width != width || frame->height != height ||frame->format != pix_fmt){/* To handle this change, one could call av_image_alloc again and* decode the following frames into another rawvideo file. */fprintf(stderr, "Error: Width, height and pixel format have to be ""constant in a rawvideo file, but the width, height or ""pixel format of the input video changed:\n""old: width = %d, height = %d, format = %s\n""new: width = %d, height = %d, format = %s\n",width, height, av_get_pix_fmt_name(pix_fmt),frame->width, frame->height,av_get_pix_fmt_name(frame->format)); return -1; }video_frame_count++; static int iFrame = 0; if (frame->key_frame == 1) //如果是关键帧{sws_scale(pSWSCtx, frame->data, frame->linesize, 0,video_dec_ctx->height,pFrameRGB->data, pFrameRGB->linesize); // 保存到磁盘iFrame++; jpg_save(pFrameRGB->data[0], iFrame, width, height); }}}/* If we use frame reference counting, we own the data and need* to de-reference it when we don't use it anymore */if (*got_frame && refcount)av_frame_unref(frame); return decoded; }static int open_codec_context(int *stream_idx,AVCodecContext **dec_ctx, AVFormatContext *fmt_ctx, enum AVMediaType type){int ret, stream_index; AVStream *st; AVCodec *dec = NULL; AVDictionary *opts = NULL; ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0); if (ret < 0){fprintf(stderr, "Could not find %s stream in input file '%s'\n",av_get_media_type_string(type), src_filename); return ret; }else{stream_index = ret; st = fmt_ctx->streams[stream_index]; /* find decoder for the stream */dec = avcodec_find_decoder(st->codecpar->codec_id); if (!dec){fprintf(stderr, "Failed to find %s codec\n",av_get_media_type_string(type)); return AVERROR(EINVAL); }/* Allocate a codec context for the decoder */*dec_ctx = avcodec_alloc_context3(dec); if (!*dec_ctx){fprintf(stderr, "Failed to allocate the %s codec context\n",av_get_media_type_string(type)); return AVERROR(ENOMEM); }/* Copy codec parameters from input stream to output codec context */if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) < 0){fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n",av_get_media_type_string(type)); return ret; }/* Init the decoders, with or without reference counting */av_dict_set(&opts, "refcounted_frames", refcount ? "1" : "0", 0); if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0){fprintf(stderr, "Failed to open %s codec\n",av_get_media_type_string(type)); return ret; }*stream_idx = stream_index; }return 0; }static int get_format_from_sample_fmt(const char **fmt, enum AVSampleFormat sample_fmt){int i; struct sample_fmt_entry{enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le; } sample_fmt_entries[] = {{AV_SAMPLE_FMT_U8, "u8", "u8"},{AV_SAMPLE_FMT_S16, "s16be", "s16le"},{AV_SAMPLE_FMT_S32, "s32be", "s32le"},{AV_SAMPLE_FMT_FLT, "f32be", "f32le"},{AV_SAMPLE_FMT_DBL, "f64be", "f64le"},}; *fmt = NULL; for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++){struct sample_fmt_entry *entry = &sample_fmt_entries[i]; if (sample_fmt == entry->sample_fmt){*fmt = AV_NE(entry->fmt_be, entry->fmt_le); return 0; }}fprintf(stderr,"sample format %s is not supported as output format\n",av_get_sample_fmt_name(sample_fmt)); return -1; }int main(int argc, char **argv){int ret = 0, got_frame; int numBytes = 0; uint8_t *buffer; if (argc != 3 && argc != 4){fprintf(stderr, "usage: %s [-refcount] input_file ouput_dir\n""API example program to show how to read frames from an input file.\n""This program reads frames from a file, decodes them, and writes bmp keyframes\n""If the -refcount option is specified, the program use the\n""reference counting frame system which allows keeping a copy of\n""the data for longer than one decode call.\n""\n",argv[0]); exit(1); }if (argc == 4 && !strcmp(argv[1], "-refcount")){refcount = 1; argv++; }src_filename = argv[1]; output_dir = argv[2]; /* open input file, and allocate format context */if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0){fprintf(stderr, "Could not open source file %s\n", src_filename); exit(1); }/* retrieve stream information */if (avformat_find_stream_info(fmt_ctx, NULL) < 0){fprintf(stderr, "Could not find stream information\n"); exit(1); }if (open_codec_context(&video_stream_idx, &video_dec_ctx, fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0){video_stream = fmt_ctx->streams[video_stream_idx]; /* allocate image where the decoded image will be put */width = video_dec_ctx->width; height = video_dec_ctx->height; pix_fmt = video_dec_ctx->pix_fmt; }else{goto end; }/* dump input information to stderr */av_dump_format(fmt_ctx, 0, src_filename, 0); if (!video_stream){fprintf(stderr, "Could not find video stream in the input, aborting\n"); ret = 1; goto end; }pFrameRGB = av_frame_alloc(); numBytes = avpicture_get_size(AV_PIX_FMT_BGR24, width, height); buffer = av_malloc(numBytes); avpicture_fill((AVPicture *)pFrameRGB, buffer, AV_PIX_FMT_BGR24, width, height); pSWSCtx = sws_getContext(width, height, pix_fmt, width, height, AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL); frame = av_frame_alloc(); if (!frame){fprintf(stderr, "Could not allocate frame\n"); ret = AVERROR(ENOMEM); goto end; }/* initialize packet, set data to NULL, let the demuxer fill it */av_init_packet(&pkt); pkt.data = https://www.it610.com/article/NULL; pkt.size = 0; if (video_stream)printf("Demuxing video from file '%s' to dir: %s\n", src_filename, output_dir); /* read frames from the file */while (av_read_frame(fmt_ctx, &pkt) >= 0){AVPacket orig_pkt = pkt; do{ret = decode_packet(&got_frame, 0); if (ret < 0)break; pkt.data += ret; pkt.size -= ret; } while (pkt.size > 0); av_packet_unref(&orig_pkt); }/* flush cached frames */pkt.data = https://www.it610.com/article/NULL; pkt.size = 0; end:if (video_dec_ctx)avcodec_free_context(&video_dec_ctx); if (fmt_ctx)avformat_close_input(&fmt_ctx); if (buffer)av_free(buffer); if (pFrameRGB)av_frame_free(&pFrameRGB); if (frame)av_frame_free(&frame); return ret < 0; }static void jpg_save(uint8_t *pRGBBuffer, int iFrame, int width, int height){struct jpeg_compress_struct cinfo; struct jpeg_error_mgr jerr; char szFilename[1024]; int row_stride; FILE *fp; JSAMPROW row_pointer[1]; // 一行位图cinfo.err = jpeg_std_error(&jerr); jpeg_create_compress(&cinfo); sprintf(szFilename,"%s/image-%03d.jpg", output_dir, iFrame); //图片名字为视频名+号码fp = fopen(szFilename, "wb"); if (fp == NULL)return; jpeg_stdio_dest(&cinfo, fp); cinfo.image_width = width; // 为图的宽和高，单位为像素cinfo.image_height = height; cinfo.input_components = 3; // 在此为1,表示灰度图，如果是彩色位图，则为3cinfo.in_color_space = JCS_RGB; //JCS_GRAYSCALE表示灰度图，JCS_RGB表示彩色图像jpeg_set_defaults(&cinfo); jpeg_set_quality(&cinfo, 80, 1); jpeg_start_compress(&cinfo, TRUE); row_stride = cinfo.image_width * 3; //每一行的字节数,如果不是索引图,此处需要乘以3// 对每一行进行压缩while (cinfo.next_scanline < cinfo.image_height){row_pointer[0] = &(pRGBBuffer[cinfo.next_scanline * row_stride]); jpeg_write_scanlines(&cinfo, row_pointer, 1); }jpeg_finish_compress(&cinfo); jpeg_destroy_compress(&cinfo); fclose(fp); }cat Makefilekeyframe:keyframe.cpp g++ $< -o $@ `pkg-config --libs libavcodec libavformat libswscale libavutil` -ljpeg -fpermissive