Merged pipeline for color interpolation and edge enhancement of digital images

Abstract

A digital-camera processor receives mono-color digital pixels from an image sensor. Each mono-color pixel is red, blue, or green. The stream of pixels from the sensor has alternating green and red pixels on odd lines, and blue and green pixels on even lines in a Bayer pattern. Each mono-color pixel is white balanced by multiplying with a gain determined in a previous frame and then stored in a line buffer. A horizontal interpolator receives an array of pixels from the line buffer. The horizontal interpolator generates missing color values by interpolation within horizontal lines in the array. The intermediate results from the horizontal interpolator are stored in a column buffer, and represent one column of pixels from the line buffer. A vertical interpolator generates the final RGB value for the pixel in the middle of the column register by vertical interpolation. The RGB values are converted to YUV. The vertical interpolator also generates green values for pixels above and below the middle pixel. These green values are sent to an edge detector. The edge detector applies a filter to the 3 green values and 6 more green values from the last 2 clock cycles. When an edge is detected, an edge enhancer is activated. The edge enhancer adds a scaled factor to the Y component to sharpen the detected edge. Color enhancement is performed on the U and V components. The line buffer stores only 4 full lines of pixels and no full-frame buffer is needed.