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imgcodecs: update documentation for imwrite() to support images formats.

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Kumataro 2023-03-26 09:03:16 +09:00
parent 36a03dbdbf
commit 83a49b4f6a
1 changed files with 17 additions and 8 deletions
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25
modules/imgcodecs/include/opencv2/imgcodecs.hpp
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@ -218,17 +218,26 @@ CV_EXPORTS_W bool imreadmulti(const String& filename, CV_OUT std::vector<Mat>& m
/** @brief Saves an image to a specified file.
The function imwrite saves the image to the specified file. The image format is chosen based on the
filename extension (see cv::imread for the list of extensions). In general, only 8-bit
filename extension (see cv::imread for the list of extensions). In general, only 8-bit unsigned (CV_8U)
single-channel or 3-channel (with 'BGR' channel order) images
can be saved using this function, with these exceptions:
- 16-bit unsigned (CV_16U) images can be saved in the case of PNG, JPEG 2000, and TIFF formats
- 32-bit float (CV_32F) images can be saved in TIFF, OpenEXR, and Radiance HDR formats; 3-channel
(CV_32FC3) TIFF images will be saved using the LogLuv high dynamic range encoding (4 bytes per pixel)
- PNG images with an alpha channel can be saved using this function. To do this, create
8-bit (or 16-bit) 4-channel image BGRA, where the alpha channel goes last. Fully transparent pixels
should have alpha set to 0, fully opaque pixels should have alpha set to 255/65535 (see the code sample below).
- Multiple images (vector of Mat) can be saved in TIFF format (see the code sample below).
- With OpenEXR encoder, only 32-bit float (CV_32F) images can be saved.
- 8-bit unsigned (CV_8U) images are not supported.
- With Radiance HDR encoder, non 64-bit float (CV_64F) images can be saved.
- All images will be converted to 32-bit float (CV_32F).
- With JPEG 2000 encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- With PAM encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- With PNG encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- PNG images with an alpha channel can be saved using this function. To do this, create
8-bit (or 16-bit) 4-channel image BGRA, where the alpha channel goes last. Fully transparent pixels
should have alpha set to 0, fully opaque pixels should have alpha set to 255/65535 (see the code sample below).
- With PGM/PPM encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- With TIFF encoder, 8-bit unsigned (CV_8U), 16-bit unsigned (CV_16U),
32-bit float (CV_32F) and 64-bit float (CV_64F) images can be saved.
- Multiple images (vector of Mat) can be saved in TIFF format (see the code sample below).
- 32-bit float 3-channel (CV_32FC3) TIFF images will be saved
using the LogLuv high dynamic range encoding (4 bytes per pixel)
If the image format is not supported, the image will be converted to 8-bit unsigned (CV_8U) and saved that way.