Abstract: Disclosed are various techniques for generating gain maps. According to some embodiments, one technique for generating a gain map includes the steps of (1) accessing a high dynamic range (HDR) image, (2) accessing a standard dynamic range (SDR) image, (3) for each pixel shared between the HDR and SDR images: plotting the pixel onto a graph, wherein an HDR value of the pixel is plotted on a Y-axis of the graph and an SDR value of the pixel is plotted on an X-axis of the graph, (4) establishing a first curve that represents an approximation of the plotted pixels, (5) inverting the first curve to establish a second curve, (6) applying the second curve against the plotted pixels to establish replotted pixels, (7) generating the gain map based on the replotted pixels, and (8) embedding the gain map into the HDR image.

Abstract: This application describes techniques for preprocessing images to improve gain map compression outcomes. A gain map can be generated by comparing a first image to a second image and subsequently compressed to form a compressed gain map. The compressed gain map can combined with a compressed version of the first image to form a compressed enhanced image. The compressed enhanced image can be later uncompressed to generate an uncompressed version of the first image and the gain map applied to the uncompressed version of the first image to generate a version of the second image to provide for reproduction on a target display. The compressed version of the first image and the compressed gain map can be generated separately by an image compression module and a gain map compression module or jointly by a combined gain map generation and compression module.

Abstract: Disclosed are various techniques for utilizing gain maps. According to some embodiments, one technique for utilizing a gain map comprises (1) accessing an enhanced image that includes a high dynamic range (HDR) image and the gain map, (2) extracting the HDR image and the gain map from the enhanced image, (3) generating a standard dynamic range (SDR) image using the HDR image and the gain map, (4) receiving and applying first modification instructions against the HDR image, (5) generating second modification instructions based on at least the first modification instructions, (6) applying the second modification instructions to the SDR image, (7) generating a second gain map by comparing the HDR image against the SDR image or vice-versa, and (8) embedding the second gain map into the HDR image or the SDR image.

Abstract: An electronic device such as a watch may include a display and a light sensor located behind the display. The light sensor may be used to measure the color of external objects. During color sampling operations, the display may emit light towards the external object in front of the display while the light sensor gathers color measurements. The display may emit light of different colors and the light sensor may detect an amount of reflected light for each color, which in turn may be used to determine the color of the external object. The control circuitry may use a watch-band-specific algorithm to determine the color of watch bands and may use a clothing-specific algorithm to determine the color of clothing. The control circuitry may display the color on the display so that the face of the watch matches the user's clothing or matches the user's watch band.