An image processing unit comprising: first means for generating an image object separation mask for an image, the image object separation mask representing saliency values indicating a separation of image objects and a background area; and characterized by further comprising: second means for generating a modified image object separation mask by iteratively filtering the saliency values of the image object separation mask, the iterative filtering being adapted in response to image characteristics of the image, the image characteristics representing at least one of luminance characteristics and color characteristics, wherein the second means is arranged to determine, during iterative filtering, a value of the image object separation mask for a first picture element as a weighted average of values of the image object separation mask in the previous iteration for picture elements in an image region proximal to the first picture element, a value of the image object separation mask for respective second picture elements in said proximal image region being weighted by a weight determined by a function which is monotonically decreasing with an increased difference between the image characteristic of the first picture element and the image characteristic for a respective second picture element; third means for generating an image depth map for the image in response to the modified image object separation mask; the image depth map comprising data representing a depth of at least one image region of the image, wherein the third means (105, 205) is arranged to generate a background depth map for the background area in response to a predetermined depth profile; and to assign a depth value to a separated image object in response to a depth value of the background depth map for a proximal background area. second means for generating a modified image object separation mask by iteratively filtering the saliency values of the image object separation mask, the iterative filtering being adapted in response to image characteristics of the image, the image characteristics representing at least one of luminance characteristics and color characteristics, wherein the second means is arranged to determine, during iterative filtering, a value of the image object separation mask for a first picture element as a weighted average of values of the image object separation mask in the previous iteration for picture elements in an image region proximal to the first picture element, a value of the image object separation mask for respective second picture elements in said proximal image region being weighted by a weight determined by a function which is monotonically decreasing with an increased difference between the image characteristic of the first picture element and the image characteristic for a respective second picture element; third means for generating an image depth map for the image in response to the modified image object separation mask; the image depth map comprising data representing a depth of at least one image region of the image, wherein the third means (105, 205) is arranged to generate a background depth map for the background area in response to a predetermined depth profile; and to assign a depth value to a separated image object in response to a depth value of the background depth map for a proximal background area.