jpegtran
Perform lossless transformation of JPEG files.
TLDR
Mirror an image horizontally or vertically
$ jpegtran -flip [horizontal|vertical] [path/to/image.jpg] > [path/to/output.jpg]
Rotate an image 90, 180 or 270 degrees clockwise
$ jpegtran -rotate [90|180|270] [path/to/image.jpg] > [path/to/output.jpg]
Transpose the image across the upper left to lower right axis
$ jpegtran -transpose [path/to/image.jpg] > [path/to/output.jpg]
Transverse the image across the upper right to lower left axis
$ jpegtran -transverse [path/to/image.jpg] > [path/to/output.jpg]
Convert the image to grayscale
$ jpegtran -grayscale [path/to/image.jpg] > [path/to/output.jpg]
Crop the image to a rectangular region of width W and height H from the upper left corner, saving the output to a specific file
$ jpegtran -crop [W]x[H] -outfile [path/to/output.jpg] [path/to/image.jpg]
Crop the image to a rectangular region of width W and height H, starting at point X and Y from the upper left corner
$ jpegtran -crop [W]x[H]+[X]+[Y] [path/to/image.jpg] > [path/to/output.jpg]
