自动红眼移除算法 附c++完整代码

说起红眼算法，这个话题非常古老了。

百度百科上的描述：

“红眼”一般是指在人物摄影时，当闪光灯照射到人眼的时候，瞳孔放大而产生的视网膜泛红现象。

由于红眼现象的程度是根据拍摄对象色素的深浅决定的，如果拍摄对象的眼睛颜色较深，红眼现象便不会特别明显。

“红眼”也指传染性结膜炎。

近些年好像没有看到摄影会出现这样的情况，毕竟科技发展迅速。

记得最早看到红眼移除算法是在ACDSee 这个看图软件的编辑功能区。

当然，当时ACDSee 也没有能力做到自动去红眼，也需要进行手工操作。

红眼移除不难，其实就是把眼睛区域的颜色修正一下。

但是难就难在修复之后，不要显得太过突兀，或者破坏眼睛周围的颜色 。

这就有点难办了。

当然其实最简单的思路，就是转色域空间处理后再转回RGB。

记得在2015年的时候，

曾经一度想要寻找红眼移除过度自然的算法思路，

当时仅仅是好奇，想要学习之。

直到2016年，在一个Delphi 图像控件的源码里看到了一个红颜移除算法函数。

把代码转写成C之后验证了一下，效果不错，过度很自然。

貌似好像有点暴露年龄了，

俺也曾经是Delphi程序员来的，无比怀念Delphi7。

贴上红眼算法的Delphi源码: 

procedure _IERemoveRedEyes(bitmap: TIEBitmap; fSelx1, fSely1, fSelx2, fSely2: integer; fOnProgress: TIEProgressEvent; Sender: TObject);
var
  row, col: integer;
  nrv, bluf, redq, powr, powb, powg: double;
  per1: double;
  px: PRGB;
begin
  fSelX2 := imin(fSelX2, bitmap.Width);  dec(fSelX2);
  fSelY2 := imin(fSelY2, bitmap.Height); dec(fSelY2);
  per1 := 100 / (fSelY2 - fSelY1 + 0.5);
  for row := fSelY1 to fSelY2 do
  begin
    px := bitmap.Scanline[row];
    for col := fSelX1 to fSelX2 do
    begin
      nrv := px^.g + px^.b;
      if nrv < 1 then
        nrv := 1;
      if px^.g > 1 then
        bluf := px^.b / px^.g
      else
        bluf := px^.b;
      bluf := dMax(0.5, dMin(1.5, Sqrt(bluf)));
      redq := (px^.r / nrv) * bluf;
      if redq > 0.7 then
      begin
        powr := 1.775 - (redq * 0.75 + 0.25);
        if powr < 0 then
          powr := 0;
        powr := powr * powr;
        powb := 1 - (1 - powr) / 2;
        powg := 1 - (1 - powr) / 4;
        with px^ do
        begin
          r := Round(powr * r);
          b := Round(powb * b);
          g := Round(powg * g);
        end;
      end;
      inc(px);
    end;
    if assigned(fOnProgress) then
      fOnProgress(Sender, trunc(per1 * (row - fSelY1 + 1)));
      Application.ProcessMessages;
  end;
end;

非常非常简单的代码。

但是思路很巧妙。

不多说，各位看官自己品味一下。

先上个效果图:

说明下本文背景前提:

人脸识别暂时采用MTCNN，示例不考虑判断是否存在红眼。

人脸检测部分，详情见博文《MTCNN人脸检测 附完整C++代码》

算法步骤：

检测人脸，对齐得到人脸五个特征点。

算出两眼球之间的距离，

估算眼球的大概大小，

(示例代码采用 两眼球之间的距离的九分之一)

计算相应的半径，

按圆形修复眼球颜色即可。

完整示例代码献上：

#include "mtcnn.h"
#include "browse.h"
#define USE_SHELL_OPEN
#ifndef  nullptr
#define nullptr 0
#endif
#if defined(_MSC_VER)
#define _CRT_SECURE_NO_WARNINGS
#include <windows.h> 
#else
#include <unistd.h>
#endif
#define STB_IMAGE_STATIC
#define STB_IMAGE_IMPLEMENTATION

#include "stb_image.h"
//ref:https://github.com/nothings/stb/blob/master/stb_image.h
#define TJE_IMPLEMENTATION

#include "tiny_jpeg.h"
//ref:https://github.com/serge-rgb/TinyJPEG/blob/master/tiny_jpeg.h

#include <stdint.h>
#include "timing.h"

char saveFile[1024];

unsigned char *loadImage(const char *filename, int *Width, int *Height, int *Channels) {
    return stbi_load(filename, Width, Height, Channels, 0);
}

void saveImage(const char *filename, int Width, int Height, int Channels, unsigned char *Output) {
    memcpy(saveFile + strlen(saveFile), filename, strlen(filename));
    *(saveFile + strlen(saveFile) + 1) = 0;
    //保存为jpg
    if (!tje_encode_to_file(saveFile, Width, Height, Channels, true, Output)) {
        fprintf(stderr, "save JPEG fail.
");
        return;
    }

#ifdef USE_SHELL_OPEN
    browse(saveFile);
#endif
}

void splitpath(const char *path, char *drv, char *dir, char *name, char *ext) {
    const char *end;
    const char *p;
    const char *s;
    if (path[0] && path[1] == ':') {
        if (drv) {
            *drv++ = *path++;
            *drv++ = *path++;
            *drv = '';
        }
    }
    else if (drv)
        *drv = '';
    for (end = path; *end && *end != ':';)
        end++;
    for (p = end; p > path && *--p != '\' && *p != '/';)
        if (*p == '.') {
            end = p;
            break;
        }
    if (ext)
        for (s = end; (*ext = *s++);)
            ext++;
    for (p = end; p > path;)
        if (*--p == '\' || *p == '/') {
            p++;
            break;
        }
    if (name) {
        for (s = p; s < end;)
            *name++ = *s++;
        *name = '';
    }
    if (dir) {
        for (s = path; s < p;)
            *dir++ = *s++;
        *dir = '';
    }
}

void getCurrentFilePath(const char *filePath, char *saveFile) {
    char drive[_MAX_DRIVE];
    char dir[_MAX_DIR];
    char fname[_MAX_FNAME];
    char ext[_MAX_EXT];
    splitpath(filePath, drive, dir, fname, ext);
    size_t n = strlen(filePath);
    memcpy(saveFile, filePath, n);
    char *cur_saveFile = saveFile + (n - strlen(ext));
    cur_saveFile[0] = '_';
    cur_saveFile[1] = 0;
}

void drawPoint(unsigned char *bits, int width, int depth, int x, int y, const uint8_t *color) {
    for (int i = 0; i < min(depth, 3); ++i) {
        bits[(y * width + x) * depth + i] = color[i];
    }
}

void drawLine(unsigned char *bits, int width, int depth, int startX, int startY, int endX, int endY,
    const uint8_t *col) {
    if (endX == startX) {
        if (startY > endY) {
            int a = startY;
            startY = endY;
            endY = a;
        }
        for (int y = startY; y <= endY; y++) {
            drawPoint(bits, width, depth, startX, y, col);
        }
    }
    else {
        float m = 1.0f * (endY - startY) / (endX - startX);
        int y = 0;
        if (startX > endX) {
            int a = startX;
            startX = endX;
            endX = a;
        }
        for (int x = startX; x <= endX; x++) {
            y = (int)(m * (x - startX) + startY);
            drawPoint(bits, width, depth, x, y, col);
        }
    }
}

void drawRectangle(unsigned char *bits, int width, int depth, int x1, int y1, int x2, int y2, const uint8_t *col) {
    drawLine(bits, width, depth, x1, y1, x2, y1, col);
    drawLine(bits, width, depth, x2, y1, x2, y2, col);
    drawLine(bits, width, depth, x2, y2, x1, y2, col);
    drawLine(bits, width, depth, x1, y2, x1, y1, col);
}

#ifndef MAX
#define MAX(a, b) (((a) > (b)) ? (a): (b))
#endif
#ifndef MIN
#define MIN(a, b) (((a) > (b)) ? (b): (a))
#endif

unsigned char ClampToByte(int Value) {
    return ((Value | ((signed int) (255 - Value) >> 31)) & ~((signed int) Value >> 31));
}

int Clamp(int Value, int Min, int Max) {
    if (Value < Min)
        return Min;
    else if (Value > Max)
        return Max;
    else
        return Value;
}

void RemoveRedEyes(unsigned char *input, unsigned char *output, int width, int height, int depth, int CenterX, int CenterY,
              int Radius) {
    if (depth < 3) return;
    if ((input == nullptr) || (output == nullptr)) return;
    if ((width <= 0) || (height <= 0)) return;

    int Left = Clamp(CenterX - Radius, 0, width);
    int Top = Clamp(CenterY - Radius, 0, height);
    int Right = Clamp(CenterX + Radius, 0, width);
    int Bottom = Clamp(CenterY + Radius, 0, height);
    int PowRadius = Radius * Radius;

    for (int Y = Top; Y < Bottom; Y++) {
        unsigned char *in_scanline = input + Y * width * depth + Left * depth;
        unsigned char *out_scanline = output + Y * width * depth + Left * depth;
        int OffsetY = Y - CenterY;
        for (int X = Left; X < Right; X++) {
            int OffsetX = X - CenterX;
            int dis = OffsetX * OffsetX + OffsetY * OffsetY;
            if (dis <= PowRadius) {
                float bluf = 0;
                int Red = in_scanline[0];
                int Green = in_scanline[1];
                int Blue = in_scanline[2];
                int nrv = Blue + Green;
                if (nrv < 1) nrv = 1;
                if (Green > 1)
                    bluf = (float) Blue / Green;
                else
                    bluf = (float) Blue;
                bluf = MAX(0.5f, MIN(1.5f, sqrt(bluf)));
                float redq = (float) Red / nrv * bluf;
                if (redq > 0.7f) {
                    float powr = 1.775f - (redq * 0.75f +
                                           0.25f);
                    if (powr < 0) powr = 0;
                    powr = powr * powr;
                    float powb = 0.5f + powr * 0.5f;
                    float powg = 0.75f + powr * 0.25f;
                    out_scanline[0] = ClampToByte(powr * Red + 0.5f);
                    out_scanline[1] = ClampToByte(powg * Green + 0.5f);
                    out_scanline[2] = ClampToByte(powb * Blue + 0.5f);
                }
            }
            in_scanline += depth;
            out_scanline += depth;
        }
    }
}

int main(int argc, char **argv) {
    printf("mtcnn face detection
");
    printf("blog:http://cpuimage.cnblogs.com/
");

    if (argc < 2) {
        printf("usage: %s  model_path image_file 
 ", argv[0]);
        printf("eg: %s  ../models ../sample.jpg 
 ", argv[0]);
        printf("press any key to exit. 
");
        getchar();
        return 0;
    }
    const char *model_path = argv[1];
    char *szfile = argv[2];
    getCurrentFilePath(szfile, saveFile);
    int Width = 0;
    int Height = 0;
    int Channels = 0;
    unsigned char *inputImage = loadImage(szfile, &Width, &Height, &Channels);
    if (inputImage == nullptr || Channels != 3) return -1;
    ncnn::Mat ncnn_img = ncnn::Mat::from_pixels(inputImage, ncnn::Mat::PIXEL_RGB, Width, Height);
    std::vector<Bbox> finalBbox;
    MTCNN mtcnn(model_path);
    double startTime = now();
    mtcnn.detect(ncnn_img, finalBbox);
    double nDetectTime = calcElapsed(startTime, now());
    printf("time: %d ms.
 ", (int)(nDetectTime * 1000));
    int num_box = finalBbox.size();
    printf("face num: %u 
", num_box);
    bool draw_face_feat = false;
    for (int i = 0; i < num_box; i++) {
        if (draw_face_feat) {
            const uint8_t red[3] = {255, 0, 0};

            drawRectangle(inputImage, Width, Channels, finalBbox[i].x1, finalBbox[i].y1,
                          finalBbox[i].x2,
                          finalBbox[i].y2, red);
            const uint8_t blue[3] = {0, 0, 255};

            for (int num = 0; num < 5; num++) {
                drawPoint(inputImage, Width, Channels, (int) (finalBbox[i].ppoint[num] + 0.5f),
                          (int) (finalBbox[i].ppoint[num + 5] + 0.5f), blue);
            }
        }
        int left_eye_x = (int) (finalBbox[i].ppoint[0] + 0.5f);
        int left_eye_y = (int) (finalBbox[i].ppoint[5] + 0.5f);
        int right_eye_x = (int) (finalBbox[i].ppoint[1] + 0.5f);
        int right_eye_y = (int) (finalBbox[i].ppoint[6] + 0.5f);
        int dis_eye = (int) sqrtf((right_eye_x - left_eye_x) * (right_eye_x - left_eye_x) +
                                  (right_eye_y - left_eye_y) * (right_eye_y - left_eye_y));
        int radius = MAX(1, dis_eye / 9);
        RemoveRedEyes(inputImage, inputImage, Width, Height, Channels, left_eye_x, left_eye_y, radius);
        RemoveRedEyes(inputImage, inputImage, Width, Height, Channels, right_eye_x, right_eye_y, radius);
    }
    saveImage("_done.jpg", Width, Height, Channels, inputImage);
    free(inputImage);
    printf("press any key to exit. 
");
    getchar();
    return 0;
}

算法见 RemoveRedEyes ，这个技巧可以用于类似的图片颜色处理。

要看人脸检测的结果，把draw_face_feat 改为 true 即可。

项目地址:

https://github.com/cpuimage/MTCNN

参数也很简单，

mtcnn 模型文件路径 图片路径

例如: mtcnn ../models ../sample.jpg

用cmake即可进行编译示例代码，详情见CMakeLists.txt。

若有其他相关问题或者需求也可以邮件联系俺探讨。

邮箱地址是: 
gaozhihan@vip.qq.com