When a user disables a bundled image-codec dependency (e.g.
BUILD_ZLIB=OFF) to supply an external build but find_package()
cannot locate it, OpenCVFindLibsGrfmt.cmake silently falls back to
compiling the bundled 3rdparty version. As reported in the issue,
this is misleading: the editable ZLIB_LIBRARY_DEBUG/RELEASE cache
entries have no effect after the fallback and nothing points the
user at the real knob (ZLIB_ROOT / ZLIB_DIR).
Emit a message(WARNING) in each fallback branch, guarded by
NOT BUILD_<lib>, so the built-in fallback is no longer silent when
the user explicitly opted out of the bundled build. The warning
names the correct search variables for that library and points to
the CMake find_package / Find<lib> documentation. Applied
consistently to the zlib, libjpeg, libtiff, libpng and libwebp
fallback branches.
The existing fallback behavior is intentionally left unchanged, so
configurations that rely on the built-in fallback continue to build.
Fixes#26746
cmake: fix PNG status display when BUILD_PNG=ON #28995
### Description
Fixes#28657.
On macOS (and other Apple platforms), `BUILD_PNG=ON` is the default. The build system correctly clears `PNG_FOUND` in `OpenCVFindLibsGrfmt.cmake` and builds libpng from the bundled source. However, during the subsequent module processing phase, a downstream `find_package(PNG)` call — triggered transitively via `include()` in the **same scope** — overwrites not only `PNG_FOUND`, but also `PNG_INCLUDE_DIR`, `PNG_LIBRARIES`, and `PNG_VERSION_STRING`.
#### Root Cause: FindPNG.cmake Has Asymmetric Guards
Reading CMake 4.3's `FindPNG.cmake` (`/opt/homebrew/share/cmake/Modules/FindPNG.cmake`) reveals:
| Variable | Guard? | Fate |
|---|---|---|
| `PNG_LIBRARY` | `if(NOT PNG_LIBRARY)` at line 138 — **guarded** | Preserved |
| `PNG_PNG_INCLUDE_DIR` | `find_path(...)` at line 115 — **no guard** | **Overwritten** |
| `PNG_INCLUDE_DIR` | Derived from `PNG_PNG_INCLUDE_DIR` | **Chain-overwritten** |
| `PNG_LIBRARIES` | Derived from `PNG_LIBRARY` + `ZLIB_LIBRARY` | **Partly overwritten** |
| `PNG_VERSION_STRING` | Parsed from `PNG_PNG_INCLUDE_DIR/png.h` | **Overwritten** |
`PNG_LIBRARY` survives because FindPNG itself checks `if(NOT PNG_LIBRARY)`. But `find_path(PNG_PNG_INCLUDE_DIR)` runs unconditionally — re-searching and overwriting the bundled path with the system one.
#### Fix: Three Coordinated Changes
**Part A — Status guard** (`CMakeLists.txt`): When `BUILD_PNG=ON`, pass `FALSE` as the condition to always show `"build"` regardless of `PNG_FOUND`.
**Part B — Variable lock** (`cmake/OpenCVFindLibsGrfmt.cmake`): After building from bundled source, lock `PNG_PNG_INCLUDE_DIR` as `CACHE INTERNAL`. CMake's `find_path()` checks the cache first — if the variable exists with a valid path, it skips re-searching. The system path is never found.
**Part C — Cache cleanup** (`cmake/OpenCVFindLibsGrfmt.cmake`): Add `PNG_PNG_INCLUDE_DIR` to the `ocv_clear_internal_cache_vars()` call in the `else` branch. When a user switches `BUILD_PNG=OFF`, the cached variable is cleared, allowing `find_path` to search for the system libpng normally. Prevents stale cache leakage across configuration changes.
#### Verification (macOS 26, CMake 4.3, Homebrew libpng 1.6.58)
```
BEFORE downstream find_package(PNG):
PNG_LIBRARY = libpng
PNG_INCLUDE_DIR = .../3rdparty/libpng
PNG_VERSION_STRING = 1.6.37
AFTER downstream find_package(PNG) [with fix]:
PNG_LIBRARY = libpng ← preserved (FindPNG guard)
PNG_INCLUDE_DIR starts with .../3rdparty/libpng ← locked (Part B)
PNG_VERSION_STRING = 1.6.53 ← from bundled png.h
Status display: build (ver 1.6.53) ← correct (Part A)
```
The full reproduction and analysis are in the attached `bugReview/` directory.
### Checklist
- [x] There is a reference to the original bug report and related work
- [x] The test case is in `bugReview/` directory
- [x] Tested on macOS 26 (arm64) with CMake 4.3 + Homebrew libpng 1.6.58
- [x] Cache hygiene verified for BUILD_PNG ON→OFF→ON transitions
Animated WebP Support #25608
related issues #24855#22569
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [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
- [x] 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
[GSoC] Add GIF decode and encode for imgcodecs #25691
this is related to #24855
we add gif support for `imread`, `imreadmulti`, `imwrite` and `imwritemulti`
opencv_extra: https://github.com/opencv/opencv_extra/pull/1203
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [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
- [x] There is a reference to the original bug report and related work
- [x] 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
Add support for QNX #25832
Build and test instruction for QNX:
https://github.com/chachoi-world/qnx-ports/blob/main/opencv/README.md
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [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
- [ ] 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
3rdparty: libtiff: fix for small version expression problems for built-in tiff460 #25257Close#25256
1. fix to show build-int libtiff version
2. fix to set value of LIBTIFF_VERSION define.
(RELEASE-DATE file coms from original libtiff 4.6.0)
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [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
- [x] 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
Zlib-ng is zlib replacement with optimizations for "next generation" systems. Its optimization may benifits image library decode and encode speed such as libpng. In our tests, if using zlib-ng and libpng combination on a x86_64 machine with AVX2, the time of `imdecode` amd `imencode` will drop 20% approximately. This patch enables zlib-ng's optimization if `CV_DISABLE_OPTIMIZATION` is OFF. Since Zlib-ng can dispatch intrinsics on the fly, port work is much easier.
Related discussion: https://github.com/opencv/opencv/issues/22573
Currently, if `PNG_FOUND`, cmake scripts will check include and parse
header while we can use `PNG_VERSION_STRING` conveniently. If
`BUILD_PNG`, parse version from `PNG_LIBPNG_VER_STRING` directly is more
convenient than parsing major, minor and patch and concatenate them.
The comment of png.h also supports this.
```
/* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
```
https://github.com/glennrp/libpng/blob/libpng16/png.h#L287
This patch also modifies `ocv_parse_header_version` macro to receive
another parameter to make it more general.
The reason why changing `PNG_VERSION` to `PNG_VERSION_STRING` is to be
consistent with cmake's FindPNG.
This patch removes `HAVE_LIBPNG_PNG_H` variable because `PNG_INCLUDE_DIR`
is where to find png.h, etc according to
https://cmake.org/cmake/help/latest/module/FindPNG.html.
This patch also removes `PNG_PNG_INCLUDE_DIR` variable which is an
advanced variable used in cmake's FindPNG and is not used in opencv.
Currently, if OpenJPEG is found, only version information in summary is
correct and the information right after `find_package(OpenJPEG)` is
wrong.
```
-- Found system OpenJPEG: openjp2 (found version "")
```
The reason is OpenJPEGConfig.cmake only sets `OPENJPEG_MAJOR_VERSION`,
`OPENJPEG_MINOR_VERSION` and `OPENJPEG_BUILD_VERSION` but not `OPENJPEG_VERSION`.
Currently cmake scripttry to use regex to parse VER_MAJOR, VER_MINOR,
VER_REVISION from ZLIB_VERSION. However, ZLIB_VERSION is "1.3" which
means that there is no VER_REVISION.
You can reproduce using "-DBUILD_ZLIB=ON"
```
-- ZLib: zlib (ver 1.3.#define ZLIB_VERSION "1.3")
```
This patch add a new macro ocv_parse_header_version to extract version
information.
Add support for external libspng. #24718
Fixes https://github.com/opencv/opencv/issues/24683
Related patch to libspng: https://github.com/randy408/libspng/pull/264
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [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
- [x] 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
Add AVIF support through libavif. #23596
This is to fix https://github.com/opencv/opencv/issues/19271
Extra: https://github.com/opencv/opencv_extra/pull/1069
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [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
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake
* fix find zlib.so instead of zlib.a when NDK >= 19
On Android platform, `libopencv_imgcodecs.a` is built, expected to
depend on `libz.so`. However, since Android NDK r19, NDK's `libz.a`
is found instead of `libz.so`, leading to link error
(not found libz.a) on machines without same NDK version & direcotry.
Since Android NDK-r19, toolchain pieces are installed to
`$NDK/toolchains/llvm/prebuilt/<host-tag>/...`, including `libz.so`.
Also installed to old paths (`<NDK>/platforms` and `<NDK>/sysroot`)
in NDK r19, r20, r21, but since NDK 22, old paths are removed.
- https://github.com/android/ndk/wiki/Changelog-r19
- https://github.com/android/ndk/wiki/Changelog-r22
With this commit, `libz.so` can be correctly found in NDK<19 and NDK>=19.
`ZLIB_LIBRARIES` is also simplified as `z`, by appending match (regex)
patterns for new toolchain installation directory's libz.so's paths.
* simplify libz.so match pattern for abbreviation
Jpeg2000 OpenJPEG port
* OpenJPEG based JPEG2000 decoder implementation
Currently, the following input color spaces and depth conversions are
supported:
- 8 bit -> 8 bit
- 16 bit -> 16 bit (IMREAD_UNCHANGED, IMREAD_ANYDEPTH)
- RGB(a) -> BGR
- RGBA -> BGRA (IMREAD_UNCHANGED)
- Y(a) -> Y(a) (IMREAD_ANYCOLOR, IMREAD_GRAY, IMREAD_UNCHANGED))
- YCC -> Y (IMREAD_GRAY)
* Check for OpenJPEG availability
This enables OpenJPEG based JPEG2000 imread support by default, which
can be disabled by -DWITH_OPENJPEG=OFF. In case OpenJPEG is enabled
and found, any checks for Jasper are skipped.
* Implement precision downscaling for precision > 8 without IMREAD_UNCHANGED
With IMREAD_UNCHANGED, values are kept from the input image, without it
components are downscaled to CV_8U range.
* Enable Jpeg2K tests when OpenJPEG is available
* Add support for some more color conversions
Support IMREAD_GRAY when input color space is RGB or unspecified.
Support YUV input color space for BGR output.
* fix: problems with unmanaged memory
* fix: CMake warning - HAVE_OPENJPEG is undefined
Removed trailing whitespaces
* fix: CMake find_package OpenJPEG add minimal version
* Basic JPEG2K encoder
Images with depth CV_8U and CV_16U are supported, with 1 to 4 channels.
* feature: Improved code for OpenJPEG2000 encoder/decoder
- Removed code duplication
- Added error handlers
- Extracted functions
* feature: Update conversion openjpeg array from/to Mat
* feature: Extend ChannelsIterator to fulfill RandomAccessIterator named requirements
- Removed channels split in copyFromMatImpl. With ChannelsIterator no allocations are performed.
- Split whole loop into 2 parts in copyToMat -> where std::copy and std::transforms are called.
* fix: Applied review comments.
- Changed `nullptr` in CV_LOG* functions to `NULL`
- Added `falls through` comment in decoder color space `switch`
- Added warning about unsupported parameters for the encoder
* feature: Added decode from in-memory buffers.
Co-authored-by: Vadim Levin <vadim.levin@xperience.ai>
* created new decoder and encoder for PFM
pfm file format stores binary RGB or grayscale float images.
* added test for pfm codec
* replaced large with short licence header
* little/big-endian-check is now compile time
* fixed width/height confusion, improved big/little endian recognition, fixed scaling issue and Improved signature check
* adapted tests to handle float images well
* removed data-dependency: lena.pfm
the lena image is now loaded is pam and converted to pfm.
* fixed bug in endianess detection macro
* Added endianess detection for android and win
* removed fancy endianess detection
endianess detection will be implemented in cmake scripts soonish.
* fixed minor warnings
* fixed stupid elif defined bug
* silenced some implicit cast warnings
* replaced std::to_string with std::stringstream solution
std::to_string variant did not build on android.
* replaced new endianess macros with existing ones
* improved readability
