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.
* master: (468 commits)
added suppression for TBB valgrind issue
update CUDA architecture flags initialization
increase minimal supported CUDA toolkit to 6.5
check the CPU flag correctly
opencv_visualization: check cmdline args
provide better error messages
stop search of markers in Exif reader to prevent infinite loop
Fix calibration fail on python with CALIB_THIN_PRISM_MODEL flag
clarify CUDA arithm operations usage with mask
fixed empty image condition in resize
fixed memory leak in flann tests
fisheye: add CALIB_FIX_PRINCIPAL_POINT
get/put: more type-safety and code unification using templates
py_tutorials: fix cv2.findContours return val
imgproc: speed up threshold of 64F version using NEON and SSE * use NEON under aarch64 only * check 64F version correctly
bigdata: add test, resolve split/merge issue
Improved Carotene library linear resize evaluation precision and enabled it as HAL implementation.
persistence: fixing crash with space-only values
Removed unnecessary check for Android API level and unused flags.
Fix for median blur of 2-channel images
...
Commits:
67fe57a add fixed video
db0ae2c Restore 2.4 source branch for bug fix 6317.
97ac59c Fix a memory leak indirectly caused by cvDestroyWindow
eb40afa Add a workaround for FFmpeg's color conversion accessing past the end of the buffer
421fcf9 Rearrange CvVideoWriter_FFMPEG::writeFrame for better readability
912592d Remove "INSTALL_NAME_DIR lib" target property
bb1c2d7 fix bug on border at pyrUp
- IPP is disabled by default when compiler is mingw (couldn't make it
work)
- fixed some warnings
- fixed some `__GNUC__` version checks (for correctness and convenience)
- removed UTF-8 BOM from hough.cpp (fixes#5253)
