yolox.cpp

// ncnn
#include "layer.h"
#include "net.h"
// opencv2
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

#include <vector>
#include <iostream>

#define YOLOX_NMS_THRESH 0.45  // nms threshold
#define YOLOX_CONF_THRESH 0.25 // threshold of bounding box prob
#define YOLOX_TARGET_SIZE 640  // target image size after resize, might use 416 for small model

// YOLOX use the same focus in yolov5
class YoloV5Focus : public ncnn::Layer
{
public:
    YoloV5Focus()
    {
        one_blob_only = true;
    }

    virtual int forward(const ncnn::Mat &bottom_blob, ncnn::Mat &top_blob, const ncnn::Option &opt) const
    {
        int w = bottom_blob.w;
        int h = bottom_blob.h;
        int channels = bottom_blob.c;

        int outw = w / 2;
        int outh = h / 2;
        int outc = channels * 4;

        top_blob.create(outw, outh, outc, 4u, 1, opt.blob_allocator);
        if (top_blob.empty())
            return -100;

#pragma omp parallel for num_threads(opt.num_threads)
        for (int p = 0; p < outc; p++)
        {
            const float *ptr = bottom_blob.channel(p % channels).row((p / channels) % 2) + ((p / channels) / 2);
            float *outptr = top_blob.channel(p);

            for (int i = 0; i < outh; i++)
            {
                for (int j = 0; j < outw; j++)
                {
                    *outptr = *ptr;

                    outptr += 1;
                    ptr += 2;
                }

                ptr += w;
            }
        }

        return 0;
    }
};

DEFINE_LAYER_CREATOR(YoloV5Focus)

struct Object
{
    cv::Rect_<float> rect;
    int label;
    float prob;
};

struct GridAndStride
{
    int grid0;
    int grid1;
    int stride;
};

static inline float intersection_area(const Object &a, const Object &b)
{
    cv::Rect_<float> inter = a.rect & b.rect;
    return inter.area();
}

static void qsort_descent_inplace(std::vector<Object> &faceobjects, int left, int right)
{
    int i = left;
    int j = right;
    float p = faceobjects[(left + right) / 2].prob;

    while (i <= j)
    {
        while (faceobjects[i].prob > p)
            i++;

        while (faceobjects[j].prob < p)
            j--;

        if (i <= j)
        {
            // swap
            std::swap(faceobjects[i], faceobjects[j]);

            i++;
            j--;
        }
    }

#pragma omp parallel sections
    {
#pragma omp section
        {
            if (left < j)
                qsort_descent_inplace(faceobjects, left, j);
        }
#pragma omp section
        {
            if (i < right)
                qsort_descent_inplace(faceobjects, i, right);
        }
    }
}

static void qsort_descent_inplace(std::vector<Object> &objects)
{
    if (objects.empty())
        return;

    qsort_descent_inplace(objects, 0, objects.size() - 1);
}

static void nms_sorted_bboxes(const std::vector<Object> &faceobjects, std::vector<int> &picked, float nms_threshold)
{
    picked.clear();

    const int n = faceobjects.size();

    std::vector<float> areas(n);
    for (int i = 0; i < n; i++)
    {
        areas[i] = faceobjects[i].rect.area();
    }

    for (int i = 0; i < n; i++)
    {
        const Object &a = faceobjects[i];

        int keep = 1;
        for (int j = 0; j < (int)picked.size(); j++)
        {
            const Object &b = faceobjects[picked[j]];

            // intersection over union
            float inter_area = intersection_area(a, b);
            float union_area = areas[i] + areas[picked[j]] - inter_area;
            // float IoU = inter_area / union_area
            if (inter_area / union_area > nms_threshold)
                keep = 0;
        }

        if (keep)
            picked.push_back(i);
    }
}

static void generate_grids_and_stride(const int target_w, const int target_h, std::vector<int> &strides, std::vector<GridAndStride> &grid_strides)
{
    for (int i = 0; i < (int)strides.size(); i++)
    {
        int stride = strides[i];
        int num_grid_w = target_w / stride;
        int num_grid_h = target_h / stride;
        for (int g1 = 0; g1 < num_grid_h; g1++)
        {
            for (int g0 = 0; g0 < num_grid_w; g0++)
            {
                GridAndStride gs;
                gs.grid0 = g0;
                gs.grid1 = g1;
                gs.stride = stride;
                grid_strides.push_back(gs);
            }
        }
    }
}

static void generate_yolox_proposals(std::vector<GridAndStride> grid_strides, const ncnn::Mat &feat_blob, float prob_threshold, std::vector<Object> &objects)
{
    const int num_grid = feat_blob.h;
    const int num_class = feat_blob.w - 5;
    const int num_anchors = grid_strides.size();

    const float *feat_ptr = feat_blob.channel(0);
    for (int anchor_idx = 0; anchor_idx < num_anchors; anchor_idx++)
    {
        const int grid0 = grid_strides[anchor_idx].grid0;
        const int grid1 = grid_strides[anchor_idx].grid1;
        const int stride = grid_strides[anchor_idx].stride;

        // yolox/models/yolo_head.py decode logic
        //  outputs[..., :2] = (outputs[..., :2] + grids) * strides
        //  outputs[..., 2:4] = torch.exp(outputs[..., 2:4]) * strides
        float x_center = (feat_ptr[0] + grid0) * stride;
        float y_center = (feat_ptr[1] + grid1) * stride;
        float w = exp(feat_ptr[2]) * stride;
        float h = exp(feat_ptr[3]) * stride;
        float x0 = x_center - w * 0.5f;
        float y0 = y_center - h * 0.5f;

        float box_objectness = feat_ptr[4];
        for (int class_idx = 0; class_idx < num_class; class_idx++)
        {
            float box_cls_score = feat_ptr[5 + class_idx];
            float box_prob = box_objectness * box_cls_score;
            if (box_prob > prob_threshold)
            {
                Object obj;
                obj.rect.x = x0;
                obj.rect.y = y0;
                obj.rect.width = w;
                obj.rect.height = h;
                obj.label = class_idx;
                obj.prob = box_prob;

                objects.push_back(obj);
            }

        } // class loop
        feat_ptr += feat_blob.w;

    } // point anchor loop
}

static int detect_yolox(const cv::Mat &bgr, std::vector<Object> &objects)
{
    ncnn::Net yolox;

    yolox.opt.use_vulkan_compute = true;

    // Focus in yolov5
    yolox.register_custom_layer("YoloV5Focus", YoloV5Focus_layer_creator);

    yolox.load_param("models/yolox_nano.param"); // yolox_s
    yolox.load_model("models/yolox_nano.bin");

    int img_w = bgr.cols;
    int img_h = bgr.rows;

    int w = img_w;
    int h = img_h;
    float scale = 1.f;
    if (w > h)
    {
        scale = (float)YOLOX_TARGET_SIZE / w;
        w = YOLOX_TARGET_SIZE;
        h = h * scale;
    }
    else
    {
        scale = (float)YOLOX_TARGET_SIZE / h;
        h = YOLOX_TARGET_SIZE;
        w = w * scale;
    }
    ncnn::Mat in = ncnn::Mat::from_pixels_resize(bgr.data, ncnn::Mat::PIXEL_BGR, img_w, img_h, w, h);

    // pad to YOLOX_TARGET_SIZE rectangle
    int wpad = (w + 31) / 32 * 32 - w;
    int hpad = (h + 31) / 32 * 32 - h;
    ncnn::Mat in_pad;
    // different from yolov5, yolox only pad on bottom and right side,
    // which means users don't need to extra padding info to decode boxes coordinate.
    ncnn::copy_make_border(in, in_pad, 0, hpad, 0, wpad, ncnn::BORDER_CONSTANT, 114.f);

    ncnn::Extractor ex = yolox.create_extractor();

    ex.input("in0", in_pad);

    std::vector<Object> proposals;

    {
        ncnn::Mat out;
        ex.extract("out0", out); // 原始out0.shape: 8400 85 1 2 原始加上Permute后结果是：85 8400 1 2
        // ex.extract("out0", out);    // out0.shape: 8400 85 1 2
        std::cout << "out0.shape: " << out.w << " " << out.h << " " << out.c << " " << out.dims << std::endl;
        static const int stride_arr[] = {8, 16, 32}; // might have stride=64 in YOLOX
        std::vector<int> strides(stride_arr, stride_arr + sizeof(stride_arr) / sizeof(stride_arr[0]));
        std::vector<GridAndStride> grid_strides;
        generate_grids_and_stride(in_pad.w, in_pad.h, strides, grid_strides);
        generate_yolox_proposals(grid_strides, out, YOLOX_CONF_THRESH, proposals);
    }

    // sort all proposals by score from highest to lowest
    qsort_descent_inplace(proposals);

    // apply nms with nms_threshold
    std::vector<int> picked;
    nms_sorted_bboxes(proposals, picked, YOLOX_NMS_THRESH);

    int count = picked.size();

    objects.resize(count);
    for (int i = 0; i < count; i++)
    {
        objects[i] = proposals[picked[i]];

        // adjust offset to original unpadded
        float x0 = (objects[i].rect.x) / scale;
        float y0 = (objects[i].rect.y) / scale;
        float x1 = (objects[i].rect.x + objects[i].rect.width) / scale;
        float y1 = (objects[i].rect.y + objects[i].rect.height) / scale;

        // clip
        x0 = std::max(std::min(x0, (float)(img_w - 1)), 0.f);
        y0 = std::max(std::min(y0, (float)(img_h - 1)), 0.f);
        x1 = std::max(std::min(x1, (float)(img_w - 1)), 0.f);
        y1 = std::max(std::min(y1, (float)(img_h - 1)), 0.f);

        objects[i].rect.x = x0;
        objects[i].rect.y = y0;
        objects[i].rect.width = x1 - x0;
        objects[i].rect.height = y1 - y0;
    }

    return 0;
}

static void draw_objects(const cv::Mat &bgr, const std::vector<Object> &objects)
{
    static const char *class_names[] = {
        "person", "bicycle", "car", "motorcycle", "airplane", "bus", "train", "truck", "boat", "traffic light",
        "fire hydrant", "stop sign", "parking meter", "bench", "bird", "cat", "dog", "horse", "sheep", "cow",
        "elephant", "bear", "zebra", "giraffe", "backpack", "umbrella", "handbag", "tie", "suitcase", "frisbee",
        "skis", "snowboard", "sports ball", "kite", "baseball bat", "baseball glove", "skateboard", "surfboard",
        "tennis racket", "bottle", "wine glass", "cup", "fork", "knife", "spoon", "bowl", "banana", "apple",
        "sandwich", "orange", "broccoli", "carrot", "hot dog", "pizza", "donut", "cake", "chair", "couch",
        "potted plant", "bed", "dining table", "toilet", "tv", "laptop", "mouse", "remote", "keyboard", "cell phone",
        "microwave", "oven", "toaster", "sink", "refrigerator", "book", "clock", "vase", "scissors", "teddy bear",
        "hair drier", "toothbrush"};

    cv::Mat image = bgr.clone();

    for (size_t i = 0; i < objects.size(); i++)
    {
        const Object &obj = objects[i];

        fprintf(stderr, "%d = %.5f at %.2f %.2f %.2f x %.2f\n", obj.label, obj.prob,
                obj.rect.x, obj.rect.y, obj.rect.width, obj.rect.height);

        cv::rectangle(image, obj.rect, cv::Scalar(255, 0, 0));

        char text[256];
        sprintf(text, "%s %.1f%%", class_names[obj.label], obj.prob * 100);

        int baseLine = 0;
        cv::Size label_size = cv::getTextSize(text, cv::FONT_HERSHEY_SIMPLEX, 0.5, 1, &baseLine);

        int x = obj.rect.x;
        int y = obj.rect.y - label_size.height - baseLine;
        if (y < 0)
            y = 0;
        if (x + label_size.width > image.cols)
            x = image.cols - label_size.width;

        cv::rectangle(image, cv::Rect(cv::Point(x, y), cv::Size(label_size.width, label_size.height + baseLine)),
                      cv::Scalar(255, 255, 255), -1);

        cv::putText(image, text, cv::Point(x, y + label_size.height),
                    cv::FONT_HERSHEY_SIMPLEX, 0.5, cv::Scalar(0, 0, 0));
    }

    cv::imshow("image", image);
    cv::moveWindow("image", 0, 0);
    cv::waitKey(0);
}

int main(int argc, char **argv)
{
    cv::Mat m = cv::imread("input.png"); // 输入一张图片，BGR格式
    if (m.empty())
    {
        std::cout << "read image failed" << std::endl;
        return -1;
    }

    std::vector<Object> objects;
    detect_yolox(m, objects);

    draw_objects(m, objects);

    return 0;
}