Light-weight color image conversion like pencil drawing for high-level synthesized hardware

We are developing pencil-drawing-style image conversion software suitable for high-level synthesis, HLS, technology that automatically converts software into hardware. The pencil-drawing-style image conversion consists of the former and latter processes. The former generates the images expressing edge strengths and their directions. The latter process convolves the line segment corresponding to the edge strength with its direction. As hardware-oriented software description, the medium data across the former and latter processes are optimized. In addition, the former and latter processes are overlapped between the FIFO buffer passing the medium data. The obtained image is still a gray-scaled image. To make it support the color image, this paper inserts a process compositing the original color image with the grayed pencil-drawing-style image to not intervene in the pipelined data path behavior. As a result, an HLS tool used is expected to generate a hardware module with the ideal pipelined data path by one output data/one clock. The experimental results show that the colorization hardware had no significant performance degradation issues for circuit size, run time, or power efficiency compared to the pencil drawing hardware with grayscale. Compared with the software execution, our hardware supporting color image can achieve 4.2 times the performance improvement and 130 times power efficiency.