Attached Link: http://athens.ict.usc.edu/HDRShop/

HDRIshop is one way, but I couldn't determine if it works in OS X without downloading it. From what I read, it's just a matter of converting a "spherized" panorama from 8-bit color to a multiple-precision floating-point color system. The jpeg algorithm is probably the opposite of HDRI. In jpeg, a block of pixels gets 8-bit values from a reference pixel and a fourier transformation, so it's totally unnatural way of describing illumination from a skydome. In HDRI each pixel is independent, and its color and luminance can vary continuously over a much wider range than 256 discrete steps.