说明：  创建一幅1/f谱的噪声图象,输入参数:size,创建图象的大小 factor:调整谱spectrum = 1/(f^factor),factor = 0原始高斯噪声图象,1自然噪声,1.5 云状噪声,>=2,类似血液.
(Creates 1/f spectrum noise images. im = noiseonf(size, factor) - size of image to produce factor- controls spectrum = 1/(f^factor) factor = 0 - raw Gaussian noise image = 1 - gives the 1/f `standard drop-off for `natural images = 1.5- seems to give the most intersting `cloud patterns = 2 or greater- produces `blobby images . )