随机噪声：

>> snoise = 0.25*randn(size(original));

>> j = imadd(original,im2uint8(snoise));

>> imshow(j);

>> imwrite(j,'H:\randNoise0.25.jpg','JPG');         %imwrite可以确保保存的图片周围没有save as的白色区域

椒盐噪声：

>> j = imnoise(original,'salt & pepper',0.01);

高斯噪声：

>> j = imnoise(original,'gaussian',0,0.01);