An image processing method determines a geometric transform of a suspect image by efficiently evaluating a large number of geometric transform candidates in environments with limited processing resources. Processing resources are conserved by using complementary methods for determining a geometric transform of an embedded signal. One method excels at higher geometric distortion, and specifically, distortion caused by greater tilt angle of a camera. Another method excels at lower geometric distortion, for weaker signals. Together, the methods provide a more reliable detector of an embedded data signal in image across a larger range of distortion while making efficient use of limited processing resources in mobile devices.

This disclosure relates to advanced image signal processing technology including encoded signals and digital watermarking. One implementation is directed to a printed object comprising: a white substrate or background comprising a first area; an ink mixture printed at a first plurality of spatial locations within the first area, the ink mixture printed such that the first area comprises a second plurality of spatial locations without the ink mixture, the ink mixture comprising extender white and Green 7 ink, the ink mixture comprising a volume or weight ratio of 97.5% to 99.75% white extender and 2.5%-0.25% Green 7 ink; in which the first plurality of spatial locations is arranged in a pattern conveying an encoded signal, and in which the white substrate or background and the ink mixture comprise a spectral reflectivity difference at or around 660 nm in a difference range of 8%-30%. Of course, other implementations, methods, packages, systems and apparatus are described in this patent document.

Generation of one dimensional guilloche patterns able to be affixed on a document, each guilloche pattern being able to encode variable alphanumeric data providing a different appearance to each guilloche pattern, by formatting alphanumeric data to be encoded in the form of a predefined number of data blocks with a predefined size, generating a carrier function having a plurality of parameters, the formatted data blocks forming at least one of the parameters, and modulating the carrier function by the formatted data blocks so as to encode the alphanumeric data graphically, each data block defining a guilloche pattern, the number of data blocks defining the number of guilloche patterns, the carrier function associated with a formatted data block is modulated locally, each datum of the block being encoded locally in the guilloche pattern, by interpolation of a predefined point associated with the carrier function.

In computer vision systems that need to decode machine-readable indicia from captured imagery, it is critical to select imaging parameters (e.g., exposure interval, exposure aperture, camera gain, intensity and duration of supplemental illumination) that best allow detection of subtle features from imagery. In illustrative embodiments, a Shannon entropy metric or a KL divergence metric is used to guide selection of an optimal set of imaging parameters. In accordance with other aspects of the technology, different strategies identify which spatial locations within captured imagery should be successively examined for machine readable indicia, in order to have a greatest likelihood of success, within a smallest interval of time. A great variety of other features and arrangements are also detailed.

An example device for processing image data includes a memory configured to store an image; and one or more processors implemented in circuitry and configured to: process the image to identify a pilot signal in the image indicating a portion of the image, the pilot signal forming a boundary around the portion and having pixel values defined according to a mathematical relationship with pixel values within the portion such that the pilot signal is not perceptible to a human user and is detectable the device; determine the portion of the image using the pilot signal; and further process the portion to attempt to detect one or more contents of the portion without attempting to detect the one or more contents of the image in portions of the image outside the portion.

Examples described herein include adding a digital watermark into acoustic data. For example, the digital watermark data can be embedded using a key such that the watermark data is spread across a spectrum of the acoustic data. Thus, the data for the digital watermark may have no or minimal visible impact in the images generated using the marked acoustic data. The digital watermark may provide improved security and privacy. Moreover, the digital watermark may be incorporated into the reconstruction process of images.

A steganographic digital watermark signal is decoded from host imagery without requiring a domain transformation for signal synchronization, thereby speeding and simplifying the decoding operation. In time-limited applications, such as in supermarket point-of-sale scanners that attempt watermark decode operations on dozens of video frames every second, the speed improvement allows a greater percentage of each image frame to be analyzed for watermark data. In battery-powered mobile devices, avoidance of repeated domain transformations extends battery life. A great variety of other features and arrangements, including machine learning aspects, are also detailed.

The first image data is converted into the second image data defined by a color space that depends on an output apparatus that outputs image data. Additional information is multiplexed on the converted second image data by using a multiplex parameter.

Methods and systems for invisible watermarking of images and video are disclosed. According to one embodiment, a method for watermarking video comprises selecting a block corresponding to a subset of pixels in a video frame. The block has quantized coefficients generated during encoding of the block. A modification function is applied to a candidate quantized coefficient (QC) in the block to incorporate a bit of a watermark message. The modification function is based on a set of configuration parameters.

A method for concealing data in an image or a video stream inside a compression chain, being implemented by a computer and including a structuring and processing phase, during which at least one image is structured into blocks including coefficients, a phase of converting and quantifying blocks so as to generate converted and quantified coefficients, with entropic coding intended to code the converted and quantified coefficients. The method includes a step of concealing data, during which bits of the data are concealed by modifying converted and quantified coefficients located in a high frequency zone of at least some of the blocks that relate to the luminance component of the video stream and that are intra-coded. This modification is performed after the quantification but before the entropic coding.