DIGITAL PROCESSING APPARATUS FOR VARIABLE IMAGE-SIZE ENLARGEMENT WITH HIGH-FREQUENCY BANDWIDTH SYNTHESIS

摘要

Derives a displayed enlarged image in which the introduction of visible "staircasing", blurred edges and non-linear artifacts are eliminated to thereby produce a perceptually natural looking enlarged image that retains the "look and feel" of the input image. The use of diagonal interpolators that comprise (1) first compute means for computing the absolute values of the difference in algebraic pixel values of each of two pairs of adjacent pixels that are diagonally oriented, respectively, at a +45 DEG and -45 DEG angles with respect to the horizontal, (2) logic means for comparing these absolute values to one another to determine which has the smaller absolute value and (3) second compute means for deriving an interpolated pixel that has an algebraic value equal to the average of the algebraic pixel values of that pair of pixels that has the smaller computed absolute value, eliminates "staircasing". Blurred edges and non-linear artifacts are eliminated by (a) deriving a binary mask from a 2D Laplacian input image in which only an edge location in the Laplacian image is defined by a pair of adjacent pixels of the binary-mask having given non-zero amplitude values and all other locations in the Laplacian image are defined by pixels of the binary mask having zero amplitude values, (b) 2D expanding the binary mask with separable 3-tap low-pass filters and (c) successively multiplying diagonally-interpolated pixels by corresponding 2D expanded binary-mask and gain-control pixels followed by amplitude clipping of the product pixels with respect to given negative and positive threshold values.