Graphical content and digital processing advances have paved the path for the design, development, and implementation of a myriad of products and systems that improve our ability to manage, store, and display various digital content. From basic high-resolution thin-profile graphics displays to pocket-size high-resolution digital cameras, today's graphics processing products and systems are capable of providing better quality and better resolution graphics to the benefit of content providers and content consumers alike. The proliferation of high-resolution consumer digital cameras, both video and still digital cameras, is evidence of the impact of these advances and provides additional evidence of a need among consumers for products that are capable of generating, managing, and displaying high quality and high resolution digital images.
Generally, digital cameras operate much like a standard film camera in the aperture, shutter, and lens functions. However, the key to digital image capture is in the CCD, or charge-coupled-device, which acts as the digital “film.” The digital camera also maintains one or more processors that execute one or more graphics processing algorithms that operate on captured images to display and store them. In operation, a digital camera automatically sets the focus and exposure level required to capture a desired image. The exposure level is necessary, for like film, there is a saturation point for a CCD reached when the photodiode electron capture wells are filled. Capture is a fairly mechanical step, as the shutter is open long enough for the CCD to be bombarded with photons before further processing occurs. The CCD quantizes the image by virtue of a limited number of photodiode cells, or pixels, available to capture the photons. Current cameras have varying numbers of pixels (e.g. 1 million to 4.3 million pixels) and may have varying numbers of CCDs (e.g. one CCD to three CCDs).
The key concept of current digital cameras is that the CCD does not see color. On the contrary, it only keeps a rough count of how many photons have hit a particular point on the CCD. To make the CCD capture color images, the camera employs one or more demosaicing algorithms to recover a full image from a color mosaic image that is created by (e.g. Bayer mosaic) placing a color filter array over the CCD. With this filter, only red, green, or blue (RGB) light reached any given pixel on the CCD. The Bayer pattern is described more fully in U.S. Pat. No. 3,987,065 and is herein incorporated by reference in its entirety. The Bayer pattern attempts to simulate natural human visual response with alternating rows of RGRG and BGBG. In this way, roughly 25 percent of the pixels of any given captured image are red, 25 percent are blue, and 50 percent are green. The green emphasis is due to the increased sensitivity of the human eye to green light.
Specifically, in the Bayer mosaic, every red pixel is surrounded by four greens and four blues. Every blue pixel is surrounded by four greens and four reds. Every green pixel has two adjacent reds and two adjacent blues. Image demosaicing interpolates the colors using these neighboring pixels. Stated differently, red pixels have red and need green and blue. The four surrounding greens are averaged to provide a green value, while the four surrounding blues are averaged to provide a blue value. The same occurs for blue pixels. Green pixels, on the other hand, take an average of only two pixels each for red and blue pixels. In this manner, a typical 8-bit mosaic is transformed into a 24-bit image. This technique may work well for gradual changes but tends to introduce artifacts at the edges or at areas of great changes.
As a result of current demosaicing approaches, such as the Bayer demosaic, a bit of deception is introduced. That is the actual captured resolution is much less than the resolution claimed (e.g. 3.2 mega pixels). The red image is ¼ of the claimed resolution, as id the blue, while the green image is ½ of the claimed resolution. The final images is an interpolated combination of the three. There is further loss of resolution resulting from the display capacities of the digital camera itself (e.g. a digital camera may claim to provide an image having a resolution of 2.13 mega pixels where the output images are of 1600×1200 resolution, a mere 1.92 mega pixels). The resolution loss may be attributed to a property of the CCD that limits it as strict photon capture device. As stated each pixel/cell on the CCD sees one specific color and performs a sort of ‘count’ of photons by converting photons to storage charge, the color resolution of captured images is then a mere interpolation of the filters provided for the CCD. Further, the number of electrons collected at each pixel is linearly dependent on light level and exposure time, and nonlinearly dependent on wavelength. This adds more strain to the resolution output of such cameras.
Current practices attempt to address the limitations of current digital cameras by performing digitization, enhancement, and demosaicing of captured images. However, as stated, current demosaicing practices do not provide a basis to significantly enhance the image quality and image resolution.
From the foregoing, it is appreciated that there exists a need for a system and methods that ameliorate the shortcomings of existing practices.