函數imread從指定的文件加載圖像并返回它。如果無法讀取圖像(由于文件丟失、權限不正確、不支持或格式無效)，函數將返回一個空矩陣(Mat::data==NULL)。
目前支持以下文件格式:

Windows bitmaps - *.bmp, *.dib (always supported) JPEG files - *.jpeg, *.jpg, *.jpe (see the Note section) JPEG 2000 files - *.jp2 (see the Note section) Portable Network Graphics - *.png (see the Note section) WebP - *.webp (see the Note section) Portable image format - *.pbm, *.pgm, *.ppm *.pxm, *.pnm (always supported) PFM files - *.pfm (see the Note section) Sun rasters - *.sr, *.ras (always supported) TIFF files - *.tiff, *.tif (see the Note section) OpenEXR Image files - *.exr (see the Note section) Radiance HDR - *.hdr, *.pic (always supported) Raster and Vector geospatial data supported by GDAL (see the Note section)

該函數根據內容而不是文件擴展名來確定圖像的類型。
在彩色圖像的情況下，解碼后的圖像將以B G R順序存儲通道。
當使用IMREAD_GRAYSCALE時，如果可用，將使用編解碼器的內部灰度轉換。結果可能不同于cvtColor()的輸出
在Microsoft Windows* OS和MacOSX上，默認情況下使用OpenCV映像附帶的編解碼器(libjpeg、libpng、libtiff和libjasper)。因此，OpenCV總是可以讀取jpeg、png和tiff。在MacOSX上，也有使用本地MacOSX圖像閱讀器的選項。但是要注意，由于MacOSX中嵌入了顏色管理，因此當前這些本地圖像加載器提供的圖像具有不同的像素值。
在Linux、BSD口味和其他類似unix的開源操作系統上，OpenCV尋找與操作系統映像一起提供的編解碼器。安裝相關的包(不要忘記開發文件，例如Debian和Ubuntu中的“libjpeg-dev”)以獲得編解碼器支持，或者在CMake中打開OPENCV_BUILD_3RDPARTY_LIBS標志。
在CMake和@ref IMREAD_LOAD_GDAL中將WITH_GDAL標志設置為true以加載圖像的情況下，將使用GDAL驅動程序來解碼圖像，支持以下格式:光柵、矢量。
如果EXIF信息嵌入到圖像文件中，EXIF方向將被考慮，因此圖像將相應地旋轉，除非傳遞了@ref IMREAD_IGNORE_ORIENTATION標志。
使用imread_changed標志來保存PFM圖像中的浮點值。

Parameters filename: Name of file to be loaded. flags: Flag that can take values of cv::ImreadModes C++ default parameters flags: IMREAD_COLOR Getting OpenCV Linux You have several options of getting the OpenCV library:install it from the repository, make sure to install -dev packages because they contain headers necessary for the crate build (also check that your package contains pkg_config files).build OpenCV manually and set up the following environment variables prior to building the project with opencv crate:PKG_CONFIG_PATH for the location of *.pc files LD_LIBRARY_PATH for where to look for the installed *.so files during runtime Windows package Installing OpenCV is easy through the following sources:from chocolatey, also install llvm package, it's required for building:choco install llvm opencv also set OPENCV_LINK_LIBS, OPENCV_LINK_PATHS and OPENCV_INCLUDE_PATHS environment variables (see below for details).from vcpkg, also install llvm package, necessary for building:vcpkg install llvm opencv4[contrib,nonfree] macOS package Get OpenCV from homebrew:homebrew, be sure to also install llvm and pkg-config that are required for building: brew install llvm pkg-config opencv Manual build You can of course always compile OpenCV of the version you prefer manually. This is also supported, but it requires some additional configuration.You need to set up the following environment variables to point to the installed files of your OpenCV build: OPENCV_LINK_LIBS, OPENCV_LINK_PATHS and OPENCV_INCLUDE_PATHS (see below for details).

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