Abstract: A system and method is provided for variable bit rate encoding using a complexity ratio. Quantization parameter is calculated using a complexity ratio, which is equal to a local complexity divided by a global complexity. Complex pictures are allocated a larger bit budget relative to simple pictures. With the larger bit budget the quality of complex pictures can be maintained while reducing the overall size of the encoded video stream.

Abstract: The invention relates to the field of digital subtraction angiography. An image processing method is applied to a digitized mask (100) and to a sequence of digitized opacified images (101). A logarithmic function (105) is applied to the values of the pixels of the digitized mask and to the values of the pixels of the sequence of digitized opacified images, and then a subtraction (108) is made of the logarithmic value of each pixel of a digitized opacified image from the logarithmic value of the corresponding pixel in the digitized mask. In order to improve the quality of the images processed, a processing step (102) able to decrease certain pixel values of the digitized mask and of the digitized opacified images is applied before applying the logarithmic function.