The invention relates to techniques for dynamically adapting light sources for displays. More specifically, the present invention relates to circuits and methods for adjusting video signals and determining an intensity of a backlight on an image-by-image basis.

Embodiments of a system that includes one or more integrated circuits are described. During operation, the system may determine an intensity setting of the light source based on at least a portion of a video image, such as the portion of the transformed video image that includes spatially varying visual information in the video image.

Moreover, the system may modify the video image so that a product of the intensity setting and a transmittance associated with the modified video image approximately equals a product of a previous intensity setting and a transmittance associated with the video image. For example, the modification may include scaling brightness values in the transformed video image. Next, the system may identify a region in the video image in which the scaling of the brightness values results in a visual artifact associated with reduced contrast. For example, the region may include a bright region surrounded by a darker region.

Then, the system may reduce the scaling of the brightness values in the region to, at least partially, restore the contrast, thereby reducing the visual artifact. Additionally, the system may spatially filter the brightness values in the video image to reduce a spatial discontinuity between the brightness values of pixels within the region and the brightness values in a remainder of the video image.

Here's Apple's background on the invention: "Compact electronic displays, such as liquid crystal displays (LCDs), are increasingly popular components in a wide variety of electronic devices. For example, due to their low cost and good performance, these components are now used extensively in portable electronic devices, such as laptop computers.

"Many of these LCDs are illuminated using fluorescent light sources or light emitting diodes (LEDs). For example, LCDs are often backlit by Cold Cathode Fluorescent Lamps (CCFLs) which are located above, behind, and/or beside the display. As shown in FIG. 1, which illustrates an existing display system in an electronic device, an attenuation mechanism 114 (such as a spatial light modulator) which is located between a light source 110 (such as a CCFL) and a display 116 is used to reduce an intensity of light 112 produced by the light source 110 which is incident on the display 116. However, battery life is an important design criterion in many electronic devices and, because the attenuation operation discards output light 112, this attenuation operation is energy inefficient, and hence can reduce battery life. Note that in LCD displays the attenuation mechanism 114 is included within the display 116.

"In some electronic devices, this problem is addressed by trading off the brightness of video signals to be displayed on the display 116 with an intensity setting of the light source 110. In particular, many video images are underexposed, e.g., the peak brightness value of the video signals in these video images is less than the maximum brightness value allowed when the video signals are encoded. This underexposure can occur when a camera is panned during generation or encoding of the video images. While the peak brightness of the initial video image is set correctly (e.g., the initial video image is not underexposed), camera angle changes may cause the peak brightness value in subsequent video images to be reduced. Consequently, some electronic devices scale the peak brightness values in video images (such that the video images are no longer underexposed) and reduce the intensity setting of the light source 110, thereby reducing energy consumption and extending battery life.

"However, it is often difficult to reliably determine the brightness of video images, and thus it is difficult to determine the scaling using existing techniques. For example, many video images are encoded with black bars or non-picture portions of the video images. These non-picture portions complicate the analysis of the brightness of the video images, and therefore can create problems when determining the trade-off between the brightness of the video signals and the intensity setting of the light source 110. Moreover, these non-picture portions can also produce visual artifacts, which can degrade the overall user experience when using the electronic device.

"Additionally, because of gamma corrections associated with video cameras or imaging devices, many video images are encoded with a nonlinear relationship between brightness values and the brightness of the video images when displayed. Moreover, the spectrum of some light sources may vary as the intensity setting is changed. These effects can also complicate the analysis of the brightness of the video images and/or the determination of the appropriate trade-off between the brightness of the video image and the intensity setting of the light source 110.

"Hence what is needed is a method and an apparatus that facilitates determining the intensity setting of a light source and which reduces perceived visual artifacts without the above-described problems."

The inventors are Ulrich T. Barnhoefer, Wei H. Yao and Wei Chen. The graphic below is a block diagram illustrating a display system.

Patent number 20090160787 is for negative pixel compensation. This relates to multi-touch sensor panels that utilize an array of capacitive sensors (pixels) to detect and localize touch events, and more particularly, to the compensation of pixels having distorted readings when two or more simultaneous touch events are generated by the same poorly grounded object.

Compensation of pixels that generate erroneous readings (so-called "negative pixels"), produced when multiple touch events are generated by the same poorly grounded object on a touch sensor panel is disclosed. To minimize negative pixels, a thicker cover material and/or a lower dielectric constant can be used. Alternatively, narrower drive and sense lines can be employed. To compensate for negative pixels, a predicted negative pixel value can be computed as an indicator of pixels that are likely to be distorted.

The negative pixel value for any particular pixel can be computing by summing up the touch output values for pixels in the drive line of that pixel, summing up the touch output values for pixels in the sense line of that pixel, and then multiplying these two sums. The predicted negative pixel value is added to the measured touch output value for the pixel to compensate for artificially negative readings.

The inventors are Carl Wayne Westerman and Steve Porter Hotelling. The graphic below illustrates an exemplary touch sensor panel having an array of sensors (pixels) formed from a plurality of drive lines and a plurality of sense lines.

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