ximgproc: move accumulate functions from imgproc

[JArmandoAnaya]

This adds accumulate, accumulateSquare, accumulateProduct and accumulateWeighted to the ximgproc module, as part of the imgproc cleanup in opencv/opencv#25001. These accumulator functions are rarely used and are largely covered by core arithmetic (accumulate and accumulateWeighted by add and addWeighted, the other two by multiply and add), so they are a good fit for opencv_contrib rather than the base imgproc module.

The change comes in two commits. The first is a faithful move of the implementation from imgproc, keeping the dispatched SIMD kernel, the OpenCL kernel and the IPP paths intact; the only differences are the namespace
(cv::ximgproc) and the OpenCL kernel source reference (ocl::ximgproc::accumulate_oclsrc). The second commit applies C++17 style to the portable code paths (using-aliases instead of function-pointer typedefs, reinterpret_cast for the dispatch tables, and nullptr), leaving the IPP integration untouched.

The functions keep their existing signatures and behavior under the new cv::ximgproc namespace. The accuracy and performance tests move with them: the CPU accuracy test that previously lived in the opencv video module and the OpenCL accuracy test from imgproc are combined into a single ximgproc test, and the CPU and OpenCL performance tests are brought over as well. The tests are self-contained and generate their own input, so no opencv_extra data is required.

Part of opencv/opencv#25001.

This is one half of a linked pair and is meant to be merged together with the opencv PR that removes the functions from imgproc, so they are never defined in both modules at once:

• Issue: Clean Imgproc module opencv#25001
• opencv PR: imgproc: move accumulate functions to opencv_contrib opencv#29347

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• 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
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

[Copilot]

Pull request overview

Moves OpenCV’s accumulator routines (accumulate*) out of the base imgproc module into opencv_contrib’s ximgproc as part of the ongoing imgproc cleanup (linked to opencv/opencv#25001), preserving CPU SIMD dispatch, OpenCL, and IPP fast paths while updating tests/perf coverage under the new namespace.

Changes:

• Adds cv::ximgproc::{accumulate, accumulateSquare, accumulateProduct, accumulateWeighted} implementation with CPU dispatch + OpenCL kernels.
• Introduces a new public header (opencv2/ximgproc/accumulate.hpp) and wires it into opencv2/ximgproc.hpp.
• Moves/creates accuracy + performance tests for both CPU and OpenCL in the ximgproc module.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
modules/ximgproc/test/test_accumulate.cpp	Adds combined CPU + OpenCL accuracy tests for the moved accumulator functions.
modules/ximgproc/src/opencl/accumulate.cl	Adds OpenCL kernels for all four accumulation operations (incl. masked variants).
modules/ximgproc/src/accum.simd.hpp	Adds SIMD + portable CPU implementations and dispatch glue declarations.
modules/ximgproc/src/accum.dispatch.cpp	Adds the CPU dispatch entry points for the dispatched SIMD implementations.
modules/ximgproc/src/accum.cpp	Adds the main ximgproc implementations, including OpenCL + IPP paths and dispatch tables.
modules/ximgproc/perf/perf_accumulate.cpp	Adds CPU + OpenCL perf coverage for the accumulator functions under ximgproc.
modules/ximgproc/include/opencv2/ximgproc/accumulate.hpp	Adds the public API declarations and documentation for the moved functions.
modules/ximgproc/include/opencv2/ximgproc.hpp	Exposes the new accumulate header from the umbrella ximgproc header.
modules/ximgproc/CMakeLists.txt	Registers the new dispatched “accum” compilation unit for SIMD dispatch builds.

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