Get the image size without actually opening it

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Hello everyone

i am dealing with very big images(>2gb). i am having some memory problems.

so i wonder if there is way to get the image height without loading the images? now i am using cv::imread() and get the width by mat.rows, which is not very convenient for me.

and my second question would be if there is way to open only a portion of images? for this purpose i open the images again with cv::imread() and get the parts with cv::Mat(imageData, lineRange, sampleRange). i want to directly open the specific parts which are define by lineRange and sampleRange( whose are cv::Range).

Thanks