Change resize to letterbox to keep model pre-processing consistent (wang-xinyu#1371)

* Update model.cpp

Fix class mode pooling layer

* Change resize to letterbox to keep model pre-processing consistent

Change resize to letterbox to keep model pre-processing consistent

* Update yolov5_cls.cpp

reuse the preprocess function

* Update calibrator.cpp

* Update calibrator.h

* Update yolov5_cls.cpp

* Update yolov5_cls.cpp

* Update calibrator.h

* Update yolov5_cls.cpp

---------

Co-authored-by: Wang Xinyu <[email protected]>

Author: CharlesHuan

yolov5/src/calibrator.cpp

@@ -8,7 +8,7 @@
 #include <opencv2/opencv.hpp>
 #include <opencv2/dnn/dnn.hpp>
 
-static cv::Mat preprocess_img(cv::Mat& img, int input_w, int input_h) {
+cv::Mat preprocess_img(cv::Mat& img, int input_w, int input_h) {
   int w, h, x, y;
   float r_w = input_w / (img.cols * 1.0);
   float r_h = input_h / (img.rows * 1.0);

yolov5/src/calibrator.h

@@ -3,6 +3,9 @@
 #include "macros.h"
 #include <string>
 #include <vector>
+#include <opencv2/opencv.hpp>
+
+cv::Mat preprocess_img(cv::Mat& img, int input_w, int input_h);
 
 //! \class Int8EntropyCalibrator2
 //!

yolov5/yolov5_cls.cpp

@@ -3,6 +3,7 @@
 #include "utils.h"
 #include "model.h"
 #include "config.h"
+#include "calibrator.h"
 
 #include <iostream>
 #include <chrono>
@@ -18,7 +19,8 @@ const static int kOutputSize = kClsNumClass;
 void batch_preprocess(std::vector<cv::Mat>& imgs, float* output) {
   for (size_t b = 0; b < imgs.size(); b++) {
     cv::Mat img;
-    cv::resize(imgs[b], img, cv::Size(kClsInputW, kClsInputH));
+    // cv::resize(imgs[b], img, cv::Size(kClsInputW, kClsInputH));
+    img = preprocess_img(imgs[b], kClsInputW, kClsInputH);
     int i = 0;
     for (int row = 0; row < img.rows; ++row) {
       uchar* uc_pixel = img.data + row * img.step;