A coprocessor for graphic workstation: A proposal for line drawing applications

Resizing techniques are commonly used in graphic applications and window environments to change image size and adapt it to the video resolution. Different algorithms have been proposed to perform image reduction with different effects on the image content. In this paper we present a proposal for a graphic coprocessor, based on TMS320C80, optimized for line drawing low-loss reduction and suitable for VDT presentations. Based on DCT and local thresholding, the algorithm is characterized by fine granularity, task independence and consequently good matching with parallel processing. In the proposed system, the line drawing is split into 32*32 pixels windows. In order to perform the image reduction, each window is subject to DCT computation and inverse transformation of the only low-frequency coefficients. The reduced image is thresholded to a value function of the black pixel percentage in the original image and the reduction ratio. The coprocessor is able to reduce an A0 line drawing acquired at 300 dpi in less than 0.2 seconds, by a reduction ratio of 1/32, producing good information preservation in the new image suitable for VTD presentation