Using Geometry with quality

[anthony]

-quality is a setting for the output format. For JPEG it is a pecentage into the compression algortihtm , though has no direct relationship to the final output size. If unset it uses an estimate of the quality of the input image if that was also a JPEG.

the only way to adjust this for a specific outout size is trial and error. it is otherwise imposible to determine with any accuracy.

Web images are usally using a low quality and smaller images to improve download times. Thumbnailing is an extension of this.