Post-processed bokeh rendering using asymmetric recursive gaussian filters

A method of blurring an image using a spatially variable blur is disclosed. The method comprises the steps of: for each pixel of a scan line of pixels in the image: obtaining a measure representative of image depth at the pixel; determining a blur kernel width for the pixel based on the measure representative of image depth at the pixel; and where an increase in the determined blur kernel width with respect to a blur kernel width of a previous pixel in the scan line is detected: determining, from the determined blur kernel width, a tapered blur width adapted to provide an asymmetric filter response for the pixel; and applying the tapered blur width to a filter to output a blurred pixel value for the pixel by using a plurality of filter coefficients determined based on blur width values of one or more previously blurred pixels.