OpenCVForUnity绘制直方图

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/mseol/article/details/79282275

这次案例涉及到的新要点有，直方图计算，直方图绘制，画线。为了演示方便，做了一张灰度图的直方图，聪明的小朋友可以尝试实现画一下RGB直方图。其实函数非常简单，关键是理解OpenCVForUnity封装后的数据类型，搞清楚这些，闭着眼睛往函数里填值就可以了。

void Start()
{
    grayMat = Imgcodecs.imread(Application.dataPath + "/Textures/feature.jpg", 0);
    outputHist = new Mat();
    images = new List<Mat>();
    Core.split(grayMat, images);

    //计算直方图
    Mat mask = new Mat(); //不空即可
    MatOfInt channels = new MatOfInt(new int[] { 1 });
    MatOfInt histSize = new MatOfInt(new int[] { 256 }); ;
    MatOfFloat ranges = new MatOfFloat(new float[] { 0, 255 });
    bool accum = false; //是否累积
    Imgproc.calcHist(images, channels, mask, outputHist, histSize, ranges, accum);
    Debug.Log(outputHist);

    //画出直方图
    int scale = 1;
    Mat histPic = new Mat(256, 256 * scale, CvType.CV_8U, new Scalar(255)); //单通道255，白色
    //查找最大值和最小值
    Core.MinMaxLocResult res = Core.minMaxLoc(grayMat); //注意不要搞错Mat，是对grayMat计算
    double minValue = res.minVal;
    double maxValue = res.maxVal;
    Debug.Log("min:" + minValue + ", max:" + maxValue);

    //纵坐标缩放比例
    double rate = (256 / maxValue) * 1d;
    for (int i = 0; i < 256; i++)
    {
        //得到每个i和箱子的值
        //float value = outputHist.at<float>(i);
        byte[] byteArray = new byte[grayMat.width() * grayMat.height()];
        Utils.copyFromMat<byte>(grayMat, byteArray);
        float value = (float)byteArray[i];
        //Debug.Log(value);
        //画直线
        Imgproc.line(histPic, new Point(i * scale, 256), new Point(i * scale, 256 - value * rate), new Scalar(0)); //单通道0，黑色
    }

    Texture2D t2d = new Texture2D(histPic.width(), histPic.height());
    Sprite sp = Sprite.Create(t2d, new UnityEngine.Rect(0, 0, t2d.width, t2d.height), Vector2.zero);
    m_showImage.sprite = sp;
    m_showImage.preserveAspect = true;
    Utils.matToTexture2D(histPic, t2d);
}

最终效果