Bitmaps TIFFS and JPEGS

Before we leave this introduction to webcams, I would like to add a few words on the subject of image file formats, just in case anyone embarking on webcam work is an image processing novice, too. Most images that are displayed on the web or are sent in e-mails are in the jpeg format and have a file name ending in ".jpg." Unlike large, lossless, bitmap (.bmp) and tiff (.tif) files, jpeg files feature lossy image compression. In other words, the size the image takes up on your PC can be reduced considerably at the cost of image quality. Jpeg images are fairly compact, even with zero compression, but to make them smaller they employ a clever mathematical transform that looks at each 8 x 8 pixel block and creates a compact code to economically summarize the data (color and brightness) within each block. With the maximum compression (lowest quality and smallest file size), some 8 x 8 blocks will actually dissolve into one solid 8 x 8 slab with no interior color or brightness variations. We do not want this, as it will wreck our planetary images. Planetary images are relatively small and the jpeg options should always be set to highest quality/lowest compression/largest file size to preserve all our good work. Use the jpeg format, to save your work, but always have it set to the highest quality. Registax always does this anyway, by default, but other packages, especially if someone else has used your PC before you, do not. You have been warned!

For the highest quality, save the image stack in 'FITS' 32 bit format before using the wavelet sliders. (FITS=Flexible Image Transport System).

CHAPTER EIGHT

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