We should all be familiar with TV ambient lighting systems such as Philips’ Ambilight, a ring of LED lights around the periphery of a TV that extend the colors at the edge of the screen to the surrounding lighting. [Shiva Rajagopal] was inspired by his tutor to look at the mechanics of generating a more accurate color representation from video frames, and produced a project using an FPGA to perform the task in real-time. It’s not an Ambilight clone, instead it is intended to produce as accurate a color representation as possible to give the impression of a TV being on for security purposes in an otherwise empty house.
The concern was that simply averaging the pixel color values would deliver a color, but would not necessarily deliver the same color that a human eye would perceive. He goes into detail about the difference between RGB and HSL color spaces, and arrives at an equation that gives an importance rating to each pixel taking into account its saturation and thus how much the human eye perceives it. As a result, he can derive his final overall color by looking at these important pixels rather than the too-dark or too-saturated pixels whose color the user’s eye will not register.
The whole project was produced on an Altera DE2-115 FPGA development and education board, and makes use of its NTSC and VGA decoding example code. All his code is available for your perusal in his appendices, and he’s produced a demo video shown here below the break.