Grayscale
Use Grayscale for decompressing and compressing, a JPEG image. This option affects how the image is displayed. Grayscale is used for speed in output optimization. When Grayscale option is checked, the color is separated from luminosity. Color takes the most time to decompress, so for previewing the image, Grayscale can be checked for speed. The output then contains 255 shades of gray.
Progressive Encoding
Use ProgressiveEncoding to specify whether the JPEG image should be encoded in a manner such that it can be decompressed and displayed progressively. It is particularly useful to use Progressive Encoding for large files, so the user won't be shown a blank screen while waiting for the whole image to decompress.
Pixel Format
Use PixelFormat to indicate the pixel format of the image. Setting Pixel Format will change the internal image and color depth. The valid values of Pixel Format are: pf1bit, pf4bit, pf8bit, pf15bit, pf16bit, pf24bit, pf32bit.
Quality
Quality determines the closeness of the saved JPEG image to the original. Setting a larger value improves image quality but also increases file size; a smaller value decreases image quality and also reduces file size. Alter it according to the need.