Display synchronization using colored anchors

A method for displaying information, comprising:

• capturing, using a client device, a secondary image of a first display screen on which at least one primary image is presented, overlaid by a symbol comprising a set of color elements having different, respective colors that encodes a digital value;
• processing the secondary image in the client device so as to decode the digital value;
• transmitting a message from the client device to a server, the message containing an indication of the specified digital value;
• receiving, in response to the message, an item of information relating to the primary image;
• and
• displaying the secondary image of the first display screen on a second display screen associated with the client device, while overlaying the item of information on the secondary image in registration with a feature of the at least one primary image.

Apparatus for distributing information, comprising:

• a processor, configured to produce a symbol to be overlaid on at least one primary image presented on a first display screen, the symbol encoding a specified digital value in a set of color elements having different, respective colors;
• and
• a communication interface, which is coupled to receive a message from a client device containing an indication of the specified digital value decoded by the client device upon capturing and analyzing a secondary image of the first display screen, and to transmit to the client device, in response to the message by the processor, an item of information relating to the primary image for presentation on a second display screen associated with the client device,
• wherein transmitting the item of information causes the client device to overlay the item on the secondary image of the first display screen, which is displayed on the second display screen with the overlaid item in registration with a feature of the at least one primary image.

A device for displaying information, comprising:

• a communication interface;
• a camera module, which is configured to capture a secondary image of a first display screen on which at least one primary image is presented, overlaid by a symbol comprising a set of color elements having different, respective colors that encodes a digital value;
• and
• a processor, which is configured to process the secondary image so as to decode the digital value, to transmit a message via the communication interface to a server, the message containing an indication of the specified digital value, to receive, in response to the message, an item of information relating to the primary image, and to display the secondary image of the first display screen on a second display screen associated with the client device, while overlaying the item of information on the secondary image in registration with a feature of the at least one primary image.