[Enhancement] Require OpenCV >= 4 for cpp_api tests, remove legacy OpenCV 3 build support

[levxn]

Motivation

Fixes #433: Removes compiling option to build from older versions of OpenCV < 4

Technical Details

Updated all tests/cpp_api/*/CMakeLists.txt to require OpenCV_VERSION_MAJOR GREATER_EQUAL 4 instead of allowing EQUAL 3 OR EQUAL 4, and removed the USE_OPENCV_4 compile-time toggle. In the corresponding .cpp files, the old-API compatibility macros (CV_LOAD_IMAGE_COLOR, CV_BGR2GRAY, CV_RGB2BGR, CV_FONT_HERSHEY_SIMPLEX, CV_FILLED, CV_WINDOW_AUTOSIZE, cvDestroyWindow) are now defined unconditionally rather than gated behind #if USE_OPENCV_4, since there is no longer an OpenCV-3 code path to branch on. Also removed the legacy #include <opencv/highgui.h> fallback include that was only reachable in the OpenCV-3 branch.

Affected: basic_test, dataloader, dataloader_multithread, dataloader_tf, external_source, image_augmentation, multiple_dataloaders_test, performance_tests, performance_tests_with_depth, unit_tests, video_tests. serialization_test was already OpenCV-4-only and required no changes.

Test Plan

Configured and built each tests/cpp_api/* project individually against the system OpenCV (4.6.x) and confirmed the CMake version check now only accepts 4+, with no leftover OpenCV-3/USE_OPENCV_4 references:

for d in basic_test dataloader dataloader_tf dataloader_multithread external_source \
         multiple_dataloaders_test performance_tests performance_tests_with_depth \
         unit_tests video_tests image_augmentation serialization_test; do
  echo "=== $d ==="
  rm -rf "tests/cpp_api/$d/build_verify"
  cmake -S "tests/cpp_api/$d" -B "tests/cpp_api/$d/build_verify" 2>&1 | grep -i "opencv\|error"
  cmake --build "tests/cpp_api/$d/build_verify" -j"$(nproc)" 2>&1 | tail -n 20
done

# confirm no leftover OpenCV<4 gating/macros remain anywhere in the test tree
grep -rn "USE_OPENCV_4\|OpenCV_VERSION_MAJOR.*EQUAL 3\|CV_LOAD_IMAGE_COLOR\|CV_BGR2GRAY\|CV_RGB2BGR\|CV_FONT_HERSHEY_SIMPLEX\|CV_FILLED\|CV_WINDOW_AUTOSIZE\|cvDestroyWindow\|opencv/highgui.h" tests/cpp_api/

Test Result

All 11 updated cpp_api test projects configured and built cleanly against OpenCV 4.6.x, each reporting:

-- OpenCV Found -- Version-4.6.X Supported
[100%] Built target <test_name>

for: basic_test, dataloader, dataloader_tf, dataloader_multithread, external_source, multiple_dataloaders_test, performance_tests, performance_tests_with_depth, unit_tests, video_tests, image_augmentation.

Follow-up grep confirms the CMake OpenCV_VERSION_MAJOR check now only appears as GREATER_EQUAL 4 (including serialization_test, unchanged), with zero remaining hits for USE_OPENCV_4 or any OpenCV-3-only code path.

[sruthi0107]

OpenCV>=4, Build succeeds and all 21/21 ctests pass. With OpenCV 3.x, ctests degrade gracefully to a warning and 21/21 pass. Tested on gfx1100:

Running tests...
Test project /home/sruthi/rocAL/build-pr-507
      Start  1: basic_test_cpu
 1/21 Test  #1: basic_test_cpu .....................   Passed    2.30 sec
      Start  2: basic_test_gpu
 2/21 Test  #2: basic_test_gpu .....................   Passed    0.37 sec
      Start  3: basic_test_gray
 3/21 Test  #3: basic_test_gray ....................   Passed    0.31 sec
      Start  4: basic_test_rgb
 4/21 Test  #4: basic_test_rgb .....................   Passed    0.36 sec
      Start  5: dataloader_multithread_cpu
 5/21 Test  #5: dataloader_multithread_cpu .........   Passed    2.48 sec
      Start  6: dataloader_multithread_gpu
 6/21 Test  #6: dataloader_multithread_gpu .........   Passed    2.73 sec
      Start  7: performance_tests_cpu
 7/21 Test  #7: performance_tests_cpu ..............   Passed    1.51 sec
      Start  8: performance_tests_gpu
 8/21 Test  #8: performance_tests_gpu ..............   Passed    0.39 sec
      Start  9: performance_tests_with_depth_cpu
 9/21 Test  #9: performance_tests_with_depth_cpu ...   Passed    1.56 sec
      Start 10: performance_tests_with_depth_gpu
10/21 Test #10: performance_tests_with_depth_gpu ...   Passed    0.54 sec
      Start 11: unit_tests_cpu
11/21 Test #11: unit_tests_cpu .....................   Passed   13.02 sec
      Start 12: unit_tests_gpu
12/21 Test #12: unit_tests_gpu .....................   Passed    8.98 sec
      Start 13: unit_tests_gray
13/21 Test #13: unit_tests_gray ....................   Passed    3.73 sec
      Start 14: video_tests_ffmpeg
14/21 Test #14: video_tests_ffmpeg .................   Passed   48.37 sec
      Start 15: video_tests_rocdecode
15/21 Test #15: video_tests_rocdecode ..............   Passed   15.88 sec
      Start 16: basic_test_rocjpeg_gray
16/21 Test #16: basic_test_rocjpeg_gray ............   Passed    0.41 sec
      Start 17: basic_test_rocjpeg_rgb
17/21 Test #17: basic_test_rocjpeg_rgb .............   Passed    0.45 sec
      Start 18: serialization_test_cpu
18/21 Test #18: serialization_test_cpu .............   Passed    1.19 sec
      Start 19: serialization_test_gpu
19/21 Test #19: serialization_test_gpu .............   Passed    0.34 sec
      Start 20: checkpoint_save
20/21 Test #20: checkpoint_save ....................   Passed    1.99 sec
      Start 21: checkpoint_restore
21/21 Test #21: checkpoint_restore .................   Passed    2.24 sec

100% tests passed out of 21

Total Test time (real) = 109.18 sec```

[kiritigowda]

@levxn please address the review comments

[levxn]

confirmed from other CI that

-- WARNING: OpenCV Not Found -- No Display Support

So OpenCV_FOUND is false and OpenCV_VERSION_MAJOR was never set

[levxn]

when it reaches here, due to this it throws error

CMake Error at CMakeLists.txt:59 (if):
  if given arguments:

    "OpenCV_FOUND" "AND" "GREATER_EQUAL" "4"

  Unknown arguments specified

[levxn]

@LakshmiKumar23 shall I revert it back to how it was earlier?

[LakshmiKumar23]

Sure, turns out CMake doesn't take the false as a short circuit like C++. Let's revert