有没有什么功能等同于Matlab在OpenCV中的imadjust with C++？

Question

我习惯使用 imadjust 在 Matlab 中进行对比度增强。 OpenCV 中是否有任何等效函数？

A google 搜索给出了 OpenCV documentation on brightness and contrast enhancement but it uses for loops which might be inefficient. Even if we make it efficient by using Matrix expressions, it is not equivalent to what imadjust。

OpenCV 中是否有任何内置函数或任何有效的方法来完成任务？

我看到了相关的帖子，但是they link to the OpenCV doc I mentioned above or they suggest Histogram Equalization and thresholding。我更喜欢 imadjust 而不是直方图均衡化，并且阈值化似乎不会像这样执行对比度增强。

如有任何帮助，我们将不胜感激。

Answer 1

你可以试着问问这里的人： http://opencv-users.1802565.n2.nabble.com/imadjust-matlab-function-with-stretchlim-OpenCV-implementation-td6253242.html

他的实现基于此： http://www.mathworks.com/matlabcentral/fileexchange/12191-bilateral-filtering

文件应如下所示，但我不确定它是否有效：

void
getOptimalImgAdjustParamsFromHist (IplImage* p_img,unsigned int* p_optminmaxidx, int p_count)
{
  int numBins = 256;
  CvMat* bins = cvCreateMat(1,numBins,CV_8UC1);
  calcHistogram(p_img,bins,numBins);
  int sumlow = 0, sumhigh = 0;
  int low_idx = 0, high_idx = 0;
  for (unsigned int i = 0; i < numBins; i++) {
    float curval = (float) cvGetReal1D (bins, (i));
    sumlow += curval;
    if (sumlow >= p_count) {
      low_idx = i;
      break;
    }
  }
  for (unsigned int i = numBins - 1 ; i >= 0; i--) {
    float curval = (float) cvGetReal1D (bins, (i));
    sumhigh += curval;
    if (sumhigh >= p_count) {
      high_idx = i;
      break;
    }
  }
  cvReleaseMat(&bins);
  p_optminmaxidx[OPTMINIDX] = low_idx;
  p_optminmaxidx[OPTMAXIDX] = high_idx;
}

IplImage *
imageAdjust (IplImage * p_img)
{
  CvSize framesize = cvGetSize (p_img);
  int low_count = round (framesize.width * framesize.height * 0.01);
  unsigned int *optminmaxidx = new unsigned int [2];
  getOptimalImgAdjustParamsFromHist (p_img, optminmaxidx,low_count);
  int range = optminmaxidx[OPTMAXIDX] - optminmaxidx[OPTMINIDX];
  IplImage *adjustedImg = p_img;
  for (int i = 0; i < framesize.height; i++)
    for (int j = 0; j < framesize.width; j++) {
      unsigned int val = (unsigned int) getData (p_img, i, j);
      unsigned int newval = 0;
      if (val <= optminmaxidx[OPTMINIDX]) {
        newval = 0;
        setData (adjustedImg, i, j, (uchar) newval);
      } else if (val >= optminmaxidx[OPTMAXIDX]) {
        newval = 255;
        setData (adjustedImg, i, j, (uchar) newval);
      } else {
        newval =
            (unsigned int) round ((double) (((double) val -
                    (double) optminmaxidx[OPTMINIDX]) * (double) (255.0 /
                    (double) range)));
        setData (adjustedImg, i, j, (uchar) newval);
      }
    }
  delete[]optminmaxidx;
  return adjustedImg;
}

希望对您有所帮助。很棒

Answer 2

OpenCV 中没有内置解决方案来执行直方图拉伸，但您可以在循环中轻松完成。

imadjust 允许 select 上界和下界的公差，或者直接是边界，所以你需要比简单的 for 循环多一点逻辑。

您可以在实施自己的示例时参考以下示例：

#include <opencv2\opencv.hpp>
#include <vector>
#include <algorithm>

using namespace std;
using namespace cv;

void imadjust(const Mat1b& src, Mat1b& dst, int tol = 1, Vec2i in = Vec2i(0, 255), Vec2i out = Vec2i(0, 255))
{
    // src : input CV_8UC1 image
    // dst : output CV_8UC1 imge
    // tol : tolerance, from 0 to 100.
    // in  : src image bounds
    // out : dst image buonds

    dst = src.clone();

    tol = max(0, min(100, tol));

    if (tol > 0)
    {
        // Compute in and out limits

        // Histogram
        vector<int> hist(256, 0);
        for (int r = 0; r < src.rows; ++r) {
            for (int c = 0; c < src.cols; ++c) {
                hist[src(r,c)]++;
            }
        }

        // Cumulative histogram
        vector<int> cum = hist;
        for (int i = 1; i < hist.size(); ++i) {
            cum[i] = cum[i - 1] + hist[i];
        }

        // Compute bounds
        int total = src.rows * src.cols;
        int low_bound = total * tol / 100;
        int upp_bound = total * (100-tol) / 100;
        in[0] = distance(cum.begin(), lower_bound(cum.begin(), cum.end(), low_bound));
        in[1] = distance(cum.begin(), lower_bound(cum.begin(), cum.end(), upp_bound));

    }

    // Stretching
    float scale = float(out[1] - out[0]) / float(in[1] - in[0]);
    for (int r = 0; r < dst.rows; ++r)
    {
        for (int c = 0; c < dst.cols; ++c)
        {
            int vs = max(src(r, c) - in[0], 0);
            int vd = min(int(vs * scale + 0.5f) + out[0], out[1]);
            dst(r, c) = saturate_cast<uchar>(vd);
        }
    }
}

int main()
{
    Mat3b img = imread("path_to_image");

    Mat1b gray;
    cvtColor(img, gray, COLOR_RGB2GRAY);

    Mat1b adjusted;
    imadjust(gray, adjusted);

    // int low_in, high_in, low_out, high_out
    // imadjust(gray, adjusted, 0, Vec2i(low_in, high_in), Vec2i(low_out, high_out));

    return 0;
}

输入图像：

输出调整图像：

Answer 3

这里有 imadjust 和 stretchlim 的实现：

https://github.com/joshdoe/opencv/blob/1d319f683f6b9a8b0c7cbe2abdc9664f0dac919f/modules/imgproc/src/imadjust.cpp

有没有什么功能等同于Matlab在OpenCV中的imadjust with C++？

Is there any function equivalent to Matlab's imadjust in OpenCV with C++?

c++

matlab

opencv

image-processing