I don't think that's quite accurate. Jpeg compresses images by breaking the image up into small boxes, and then for each box, finding a set of weights to use to sum a set of known reference images such that the sum approximates the original box. Storing those weights takes up a lot less space than the individual pixels.
If you save an image as jpeg and then re-save it again without modification, the image won't degrade much after the first save because all the information that couldn't be represented as a sum of weighted reference images is gone, and what's left is the data that can be accurately represented as those weights.
If you manipulate the image, though, such as change the resolution or shift pixels around, the resulting bitmap may lose information again when converted to a jpeg. Also, if you take a highly compressed image, modify it, and then save it with a higher quality compression setting, the modified area will have more "information" in it than the rest of the image.
I don't think that's quite accurate. Jpeg compresses images by breaking the image up into small boxes, and then for each box, finding a set of weights to use to sum a set of known reference images such that the sum approximates the original box. Storing those weights takes up a lot less space than the individual pixels.
If you save an image as jpeg and then re-save it again without modification, the image won't degrade much after the first save because all the information that couldn't be represented as a sum of weighted reference images is gone, and what's left is the data that can be accurately represented as those weights.
If you manipulate the image, though, such as change the resolution or shift pixels around, the resulting bitmap may lose information again when converted to a jpeg. Also, if you take a highly compressed image, modify it, and then save it with a higher quality compression setting, the modified area will have more "information" in it than the rest of the image.