Merge pull request #28664 from pratham-mcw:armpl_dft_opt

Add ARMPL support for DFT Function #28664

- This PR introduces hal/armpl/ with implementation of 1D, 2D DFT and DCT routines using ARM Performance Libraries as a custom HAL replacement for OpenCV's DFT & DCT Function.
- ArmPL MSI package is automatically downloaded and extracted via CMake when building on Windows ARM64, with a WITH_ARMPL option that defaults to ON for that platform.
- Forward and inverse real DFT calls in dxt.cpp are routed through ArmPL when available, with scaling applied only when needed.
- Test error thresholds in test_dxt.cpp are relaxed (from 1e-5 to 2e-4 for float ) to account for numerical differences between ArmPL and OpenCV's reference DFT results.

**Performance Benchmarks :**
<img width="993" height="835" alt="image" src="https://github.com/user-attachments/assets/76def647-6d20-4bce-8bc9-7363e723669f" />

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch

cmake/OpenCVFindARMPL.cmake

@@ -0,0 +1,172 @@
+if(NOT AARCH64 AND NOT ARM64 AND NOT CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|arm64|ARM64")
+    return()
+endif()
+
+if(NOT WITH_ARMPL)
+    return()
+endif()
+
+set(ARMPL_ROOT_DIR "" CACHE PATH "Path to ARM Performance Libraries root directory")
+
+if(NOT ARMPL_ROOT_DIR)
+  if(DEFINED ENV{ARMPL_DIR})
+    set(ARMPL_ROOT_DIR "$ENV{ARMPL_DIR}")
+  endif()
+endif()
+
+find_path(ARMPL_INCLUDE_DIR
+  NAMES armpl.h
+  HINTS
+    "${ARMPL_ROOT_DIR}/include"
+    "${ARMPL_ROOT_DIR}/include_lp64"
+  PATHS
+    /opt/arm/armpl/include
+    /usr/include/armpl
+    ENV ARMPL_DIR
+  PATH_SUFFIXES include
+  NO_DEFAULT_PATH
+)
+
+if(WITH_OPENMP AND OpenMP_CXX_FOUND)
+  set(ARMPL_USE_OPENMP TRUE)
+  set(ARMPL_LIB_CANDIDATES
+    armpl_lp64_mp
+    armpl_ilp64_mp
+  )
+else()
+  set(ARMPL_USE_OPENMP FALSE)
+  set(ARMPL_LIB_CANDIDATES
+    armpl_lp64
+    armpl_ilp64
+  )
+endif()
+
+set(ARMPL_LIB_FOUND FALSE)
+set(ARMPL_LIB_NAME "")
+set(ARMPL_LIB_FILE "")
+
+foreach(lib_candidate ${ARMPL_LIB_CANDIDATES})
+  if(WIN32)
+    set(ARMPL_LIB_FILE_DLL "${ARMPL_ROOT_DIR}/lib/${lib_candidate}.dll.lib")
+    set(ARMPL_LIB_FILE_LIB "${ARMPL_ROOT_DIR}/lib/${lib_candidate}.lib")
+    if(EXISTS "${ARMPL_LIB_FILE_DLL}")
+      set(ARMPL_LIB_FILE "${ARMPL_LIB_FILE_DLL}")
+      set(ARMPL_LIB_NAME "${lib_candidate}")
+      set(ARMPL_LIB_FOUND TRUE)
+      break()
+    elseif(EXISTS "${ARMPL_LIB_FILE_LIB}")
+      set(ARMPL_LIB_FILE "${ARMPL_LIB_FILE_LIB}")
+      set(ARMPL_LIB_NAME "${lib_candidate}")
+      set(ARMPL_LIB_FOUND TRUE)
+      break()
+    endif()
+  else()
+    set(ARMPL_LIB_FILE "${ARMPL_ROOT_DIR}/lib/lib${lib_candidate}.a")
+    if(EXISTS "${ARMPL_LIB_FILE}")
+      set(ARMPL_LIB_NAME "${lib_candidate}")
+      set(ARMPL_LIB_FOUND TRUE)
+      break()
+    endif()
+  endif()
+endforeach()
+
+if(NOT ARMPL_LIB_FOUND)
+  find_library(ARMPL_LIBRARY_FALLBACK
+    NAMES ${ARMPL_LIB_CANDIDATES}
+    HINTS "${ARMPL_ROOT_DIR}/lib"
+    PATHS
+      /opt/arm/armpl/lib
+      /usr/lib/armpl
+      ENV ARMPL_DIR
+    PATH_SUFFIXES lib
+    NO_DEFAULT_PATH
+  )
+  if(ARMPL_LIBRARY_FALLBACK)
+    set(ARMPL_LIB_FILE "${ARMPL_LIBRARY_FALLBACK}")
+    get_filename_component(ARMPL_LIB_NAME "${ARMPL_LIBRARY_FALLBACK}" NAME_WE)
+    string(REGEX REPLACE "^lib" "" ARMPL_LIB_NAME "${ARMPL_LIB_NAME}")
+    set(ARMPL_LIB_FOUND TRUE)
+  endif()
+endif()
+
+if(NOT ARMPL_INCLUDE_DIR OR NOT ARMPL_LIB_FOUND)
+  message(WARNING
+    "ARM Performance Libraries: NOT FOUND. "
+    "Please install ArmPL manually and set -DARMPL_ROOT_DIR=<path>. "
+    "Download from: https://developer.arm.com/Tools%20and%20Software/Arm%20Performance%20Libraries"
+  )
+  return()
+endif()
+
+set(ARMPL_VERSION_STR "unknown")
+if(EXISTS "${ARMPL_INCLUDE_DIR}/armpl.h")
+  file(STRINGS "${ARMPL_INCLUDE_DIR}/armpl.h" ARMPL_VERSION_MAJOR_LINE
+    REGEX "#define ARMPL_VERSION_MAJOR")
+  file(STRINGS "${ARMPL_INCLUDE_DIR}/armpl.h" ARMPL_VERSION_MINOR_LINE
+    REGEX "#define ARMPL_VERSION_MINOR")
+  if(ARMPL_VERSION_MAJOR_LINE AND ARMPL_VERSION_MINOR_LINE)
+    string(REGEX REPLACE ".*ARMPL_VERSION_MAJOR[ \t]+([0-9]+).*" "\\1"
+      ARMPL_VERSION_MAJOR "${ARMPL_VERSION_MAJOR_LINE}")
+    string(REGEX REPLACE ".*ARMPL_VERSION_MINOR[ \t]+([0-9]+).*" "\\1"
+      ARMPL_VERSION_MINOR "${ARMPL_VERSION_MINOR_LINE}")
+    set(ARMPL_VERSION_STR "${ARMPL_VERSION_MAJOR}.${ARMPL_VERSION_MINOR}")
+  else()
+    file(STRINGS "${ARMPL_INCLUDE_DIR}/armpl.h" ARMPL_BUILD_LINE
+      REGEX "#define ARMPL_BUILD")
+    if(ARMPL_BUILD_LINE)
+      string(REGEX REPLACE ".*ARMPL_BUILD[ \t]+([0-9]+).*" "\\1"
+        ARMPL_VERSION_STR "${ARMPL_BUILD_LINE}")
+    else()
+      string(REGEX MATCH "armpl_([0-9]+\\.[0-9]+)" ARMPL_VERSION_MATCH "${ARMPL_ROOT_DIR}")
+      if(CMAKE_MATCH_1)
+        set(ARMPL_VERSION_STR "${CMAKE_MATCH_1}")
+      endif()
+    endif()
+  endif()
+endif()
+
+if(ARMPL_USE_OPENMP)
+  message(STATUS "ArmPL: OpenMP enabled, using parallel version (${ARMPL_LIB_NAME})")
+else()
+  message(WARNING
+    "ArmPL: OpenMP is not enabled. "
+    "Using serial version of ArmPL (${ARMPL_LIB_NAME}). "
+    "For better performance enable OpenMP with -DWITH_OPENMP=ON"
+  )
+endif()
+
+if(NOT TARGET armpl)
+  if(WIN32)
+    add_library(armpl SHARED IMPORTED)
+    find_file(ARMPL_DLL
+      NAMES "${ARMPL_LIB_NAME}.dll"
+      HINTS "${ARMPL_ROOT_DIR}/bin"
+      NO_DEFAULT_PATH
+    )
+    set_target_properties(armpl PROPERTIES
+      IMPORTED_IMPLIB               "${ARMPL_LIB_FILE}"
+      IMPORTED_LOCATION             "${ARMPL_DLL}"
+      INTERFACE_INCLUDE_DIRECTORIES "${ARMPL_INCLUDE_DIR}"
+    )
+  else()
+    add_library(armpl UNKNOWN IMPORTED)
+    set_target_properties(armpl PROPERTIES
+      IMPORTED_LOCATION             "${ARMPL_LIB_FILE}"
+      INTERFACE_INCLUDE_DIRECTORIES "${ARMPL_INCLUDE_DIR}"
+    )
+  endif()
+  if(ARMPL_USE_OPENMP)
+    set_target_properties(armpl PROPERTIES
+      INTERFACE_LINK_LIBRARIES OpenMP::OpenMP_CXX
+    )
+  endif()
+endif()
+
+set(ARMPL_LIBRARIES    armpl                  CACHE INTERNAL "ArmPL libraries")
+set(ARMPL_INCLUDE_DIRS "${ARMPL_INCLUDE_DIR}" CACHE INTERNAL "ArmPL include dirs")
+set(ARMPL_INCLUDE_PATH "${ARMPL_INCLUDE_DIR}" CACHE INTERNAL "ArmPL include path")
+set(ARMPL_LIBRARY      "${ARMPL_LIB_FILE}"    CACHE INTERNAL "ArmPL library path")
+set(ARMPL_LIB_NAME     "${ARMPL_LIB_NAME}"    CACHE INTERNAL "ArmPL library variant")
+set(ARMPL_VERSION_STR  "${ARMPL_VERSION_STR}" CACHE INTERNAL "ArmPL version")
+set(ARMPL_ROOT_DIR     "${ARMPL_ROOT_DIR}"    CACHE PATH     "ArmPL root directory")
+set(HAVE_ARMPL         TRUE                   CACHE BOOL     "ArmPL found and enabled" FORCE)