An image processing apparatus and method, an image processing system and a training method are disclosed. The image processing method comprises: receiving an input image; and inputting the input image to K stages of cascaded decoding units, to process the input image to obtain an output image, wherein an ith stage of decoding unit receives mK+1−i input images and outputs mK−i output images, a resolution of the output images is greater than a resolution of the input images, and the number of image components of the output images is less than the number of image components of the input images, where K, i and m are positive integers and 1≤i≤K.