1. A computer implemented method for generating an image on a display that includes a plurality of pixels, the image representing a plurality of transactions as lines connecting points in the display indicative of a source and an origin for the respective transactions, the method comprising: successively rendering lines via the computer, the lines representing each of the plurality of transactions into an image buffer, the rendering including: for each of the lines, using the computer to perform an anti-aliasing process to determine a coverage value for each pixel of the display, the coverage value representing the extent to which the line covers each pixel; and within the image buffer, maintaining a record of a cumulative coverage value for each pixel of the display; when the lines representing each of the plurality of transactions have been rendered into the image buffer, determining, using the computer, a maximum and a minimum of the cumulative coverage values stored in the image buffer; scaling, using the computer, the cumulative coverage value for each pixel based on the determined maximum and minimum cumulative coverage values; and rendering, using the computer, each pixel onto the display by using the scaled cumulative coverage value to determine a transparency for the pixel.