Specify the compression factor for RGB channels between 0 and 100. The default is 75.
In case of lossy compression (default), a small factor produces a smaller file with lower quality. Best quality is achieved by using a value of 100.
In case of lossless compression (specified by the −lossless option), a small factor enables faster compression speed, but produces a larger file. Maximum compression is achieved by using a value of 100.
−z int
