"Error: 'IplImage' does not name a type when trying to build darknet with OpenCV and CUDA?

Question

I am trying to use Darkent with OpenCV and CUDA. I installed darknet according to these instructions:

https://pjreddie.com/darknet/install/

I installed CUDA according to these instructions:

https://docs.nvidia.com/cuda/cuda-installation-guide-linux/index.html

Finally, I installed OpenCV according to these instructions:

http://www.linuxfromscratch.org/blfs/view/svn/general/opencv.html

I then added the following lines to the end of my bashrc:

export PATH=$PATH:/usr/local/cuda-11.1/bin
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda-11.1/lib64:/usr/include/opencv4
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig:/usr/include/opencv4

I was then having trouble with darknet finding the opencv library, so I added an opencv.pc file at /usr/local/lib/pkgconfig, with the following content:

prefix=/usr
exec_prefix=${prefix}
libdir=${prefix}/lib/x86_64-linux-gnu
includedir_new=${prefix}/include/opencv4

Name: OpenCV
Description: Open Source Computer Vision Library
Version: 4.5.0
Libs: -L${libdir} -lopencv_dnn -lopencv_ml -lopencv_objdetect -lopencv_shape -lopencv_stitching -lopencv_superres -lopencv_videostab -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_video -lopencv_photo -lopencv_imgproc -lopencv_flann -lopencv_core
Libs.private: -ldl -lm -lpthread -lrt
Cflags: -I${includedir_new}

Next, I modified the Makefile in the darknet directory such that GPU=1, and OPENCV=1. I ran make, but am encountering the error:

./src/image_opencv.cpp:12:1: error: ‘IplImage’ does not name a type
   12 | IplImage *image_to_ipl(image im)
      | ^~~~~~~~
compilation terminated due to -Wfatal-errors.

Any help would be greatly appreciated. I am running ubuntu 20.04, kernel 5.4.0-53-generic.

Answer 1

For OpenCV4 users who are attempting to use OpenCV in darknet,

Reprinted from (https://forums.developer.nvidia.com/t/darknet-compile-error-with-cudnn-8/141115/13): save the following in a file (patch.diff).

diff --git a/src/image_opencv.cpp b/src/image_opencv.cpp
index 7511280..c11805a 100644
--- a/src/image_opencv.cpp
+++ b/src/image_opencv.cpp
@@ -9,30 +9,34 @@ using namespace cv;

 extern "C" {
 
-IplImage *image_to_ipl(image im)
+Mat image_to_mat(image im)
 {
+    assert(im.c == 3 || im.c == 1);
     int x,y,c;
-    IplImage *disp = cvCreateImage(cvSize(im.w,im.h), IPL_DEPTH_8U, im.c);
-    int step = disp->widthStep;
+    image copy = copy_image(im);
+    constrain_image(copy);
+    if(im.c == 3) rgbgr_image(copy);
+    Mat m(im.h, im.w, CV_MAKETYPE(CV_8U, im.c));
     for(y = 0; y < im.h; ++y){
         for(x = 0; x < im.w; ++x){
             for(c= 0; c < im.c; ++c){
-                float val = im.data[c*im.h*im.w + y*im.w + x];
-                disp->imageData[y*step + x*im.c + c] = (unsigned char)(val*255);
+                float val = copy.data[c*im.h*im.w + y*im.w + x];
+                m.data[y*im.w*im.c + x*im.c + c] = (unsigned char)(val*255);
             }
         }
     }
-    return disp;
+    free_image(copy);
+    return m;
 }

-image ipl_to_image(IplImage* src)
+image mat_to_image(Mat m)
 {
-    int h = src->height;
-    int w = src->width;
-    int c = src->nChannels;
+    int h = m.rows;
+    int w = m.cols;
+    int c = m.channels();
     image im = make_image(w, h, c);
-    unsigned char *data = (unsigned char *)src->imageData;
-    int step = src->widthStep;
+    unsigned char *data = (unsigned char*)m.data;
+    int step = m.step;
     int i, j, k;

     for(i = 0; i < h; ++i){
@@ -42,26 +46,6 @@ image ipl_to_image(IplImage* src)
             }
         }
     }
-    return im;
-}
-
-Mat image_to_mat(image im)
-{
-    image copy = copy_image(im);
-    constrain_image(copy);
-    if(im.c == 3) rgbgr_image(copy);
-
-    IplImage *ipl = image_to_ipl(copy);
-    Mat m = cvarrToMat(ipl, true);
-    cvReleaseImage(&ipl);
-    free_image(copy);
-    return m;
-}
-
-image mat_to_image(Mat m)
-{
-    IplImage ipl = m;
-    image im = ipl_to_image(&ipl);
     rgbgr_image(im);
     return im;
 }
@@ -72,9 +56,9 @@ void *open_video_stream(const char *f, int c, int w, int h, int fps)
     if(f) cap = new VideoCapture(f);
     else cap = new VideoCapture(c);
     if(!cap->isOpened()) return 0;
-    if(w) cap->set(CV_CAP_PROP_FRAME_WIDTH, w);
-    if(h) cap->set(CV_CAP_PROP_FRAME_HEIGHT, w);
-    if(fps) cap->set(CV_CAP_PROP_FPS, w);
+    if(w) cap->set(CAP_PROP_FRAME_WIDTH, w);
+    if(h) cap->set(CAP_PROP_FRAME_HEIGHT, w);
+    if(fps) cap->set(CAP_PROP_FPS, w);
     return (void *) cap;
 }

@@ -123,7 +107,7 @@ void make_window(char *name, int w, int h, int fullscreen)
 {
     namedWindow(name, WINDOW_NORMAL); 
     if (fullscreen) {
-        setWindowProperty(name, CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
+        setWindowProperty(name, WND_PROP_FULLSCREEN, WINDOW_FULLSCREEN);
     } else {
         resizeWindow(name, w, h);
         if(strcmp(name, "Demo") == 0) moveWindow(name, 0, 0);

Run git apply patch.diff.

Answer 2

It seems there are some missing header lines in file /src/image_opencv.cpp, add these lines at the beginning than make it again.

#include "opencv2/core/core_c.h"
#include "opencv2/videoio/legacy/constants_c.h"
#include "opencv2/highgui/highgui_c.h"

Additionally, you have to change the line IplImage ipl = m to IplImage ipl = cvIplImage(m); in the same file.