Adaptive pixel-level color enhancement for a digital camera

A color enhancer comprising:

• a pixel input receiving a YUV pixel that includes a Y component indicating brightness but not color of the pixel, and U and V components indicating a color but not brightness of the pixel;
• a calculator, receiving pre-set scale factors, the pre-set scale factors being constant for a range of pixels in an image, for generating an enhancement factor from the Y component and from the U and V components and the pre-set scale factors;
• wherein the enhancement factor varies with the Y, U, and V components of the YUV pixel, the enhancement factor being a different value for different pixels in the image;
• a first multiplier, receiving the U component from the pixel input, for multiplying the enhancement factor from the calculator by the U component to generate an adjusted U component;
• a second multiplier, receiving the V component from the pixel input, for multiplying the enhancement factor from the calculator by the V component to generate an adjusted V component;
• and
• an output, coupled to the pixel input, the first multiplier, and the second multiplier, for outputting the Y component from the pixel input with the adjusted U and V components from the first and second multiplier as a color-enhanced pixel;
• wherein the calculator further comprises:
• a combiner, receiving the U and V components from the pixel input, for combining the U and V components to generate a colorfulness factor, the colorfulness factor representing a degree of color for the pixel;
• a function generator, receiving the Y component and the colorfulness factor and the pre-set scale factors, for generating the enhancement factor wherein the enhancement factor is larger for more colorful pixels having large colorfulness factors than for less colorful pixels having small colorfulness factors,
• wherein more color enhancement occurs for more colorful pixels;
• wherein the function generator comprises:
• a first stage, receiving the Y component from the pixel input, for generating an intermediate factor that is a function of the Y component;
• a second stage, receiving the intermediate factor from the first stage and receiving the colorfulness factor from the combiner, for generating the enhancement factor that is a function of the colorfulness factor;
• wherein the first stage outputs a maximum pre-set factor as the intermediate factor when the Y component is above an upper Y limit or below a lower Y limit,
• wherein the first stage outputs a combination of the maximum pre-set factor and a minimum pre-set factor when the Y component is between the upper Y limit and the lower Y limit,
• whereby pixels are color enhanced with the enhancement factor that is generated for each pixel that varies with the Y, U, and V components of the YUV pixel, and whereby both brightness and color of the YUV pixel can determine the enhancement factor for the YUV pixel, and whereby color enhancement is reduced when the Y component is between the upper Y limit and the lower Y limit.