While depth of field is an important cinematographic means, its use in real-time computer graphics is still limited by the computational costs that are necessary to achieve a sufficient image quality. Specifically, color bleeding artifacts between objects at different depths are most effectively avoided by a decomposition into sub-images and the independent blurring of each sub-image. This decomposition, however, can result in rendering artifacts at silhouettes of objects. We propose a new blur filter that increases the opacity of all pixels to avoid these artifacts at the cost of physically less accurate but still plausible rendering results. The proposed filter is named "opaque image blur" and is based on a glow filter that is applied to the alpha channel. We present a highly efficient GPU-based pyramid algorithm that implements this filter for depth-of-field rendering. Moreover, we demonstrate that the opaque image blur can also be used to add motion blur effects to images in real time.
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