Bazel: Cannot find headers that are in dependency

Question

I have the following structure:

C -
         app - 
               test_opencv.cpp
               BUILD
     
  thirdparty -
               opencv -
                       lib
                       include -
                                opencv4 -...
               BUILD

I have compiled the opencv library by hand using cmake and all includes are under include and the static libraries are under lib.

I have created a BUILD file that looks like this:

load("@rules_cc//cc:defs.bzl","cc_library")

cc_library(
    name = "opencv",
    srcs = glob(["opencv/lib/**/*.a"]),
    hdrs = glob(["opencv/include/opencv4/**"]),
    visibility = ["//visibility:public"],
)

Then in my app folder I have the following BUILD for my src file:

load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")

cc_library(
    name = "opencv_deps",
    linkopts = [
        "-ldl",
        "-lz",
        "-lpthread",
        "-lavutil",
        "-lavformat",
        "-lavcodec",
        "-lswscale",
        "-L/opt/homebrew/opt/ffmpeg/lib",
        "-L/opt/homebrew/Cellar/libx11/1.8.6/lib",
        "-framework Cocoa",
        "-framework Accelerate",
        "-framework CoreMedia",
        "-framework CoreVideo",
        "-framework AVFoundation"
    ],
    deps = [
        "//C/thirdparty/opencv:opencv",
    ]
)

cc_binary(
    name = "test_opencv",
    srcs = ["test_opencv.cpp"],
    deps = [
        ":opencv_deps",
        "//C/thirdparty/rerunner:rerunner",
    ],
    copts = [
        # "-IC/thirdparty/opencv/opencv/include/opencv4",
         "--std=c++17"
    ],
)

With this I get fatal error: 'opencv2/core.hpp' file not found #include <opencv2/core.hpp>.

If I comment out the include to opencv4 it works.

But this does not feel correct. I think it should be enough to use deps = ["//C/thirdparty/opencv:opencv"] to get the header files.

UPDATE

Adding includeshelped:

cc_library(
        name = "opencv",
        srcs = glob(["opencv/lib/**/*.a"]),
        hdrs = glob(["opencv/include/opencv4/**"]),
        includes = ["opencv/include/opencv4"],
        visibility = ["//visibility:public"],
    )