Printing calibration

A method comprising:

• printing a calibration target on a print target by:
• printing an first printing fluid figure on the print target;
• printing a second printing fluid figure on the print target, wherein the second printing fluid figure defines a geometric figure negatively outlined in the second printing fluid figure;
• capturing an image of the calibration target, the image having a first region of interest relating to the first printing fluid figure and a second region of interest relating to the second printing fluid figure;
• processing image data relating to the first region of interest to locate the borders of the first printing fluid figure;
• determining the location of a first printing fluid reference point on the print target based upon the located borders of the first printing fluid figure;
• processing image data relating to the second region of interest to locate geometric features of the geometric figure defined by the second printing fluid figure;
• determining the location of a second printing fluid reference point on the print target by matching the located geometric features with reference geometric features from a reference geometric figure;
• and
• determining a geometric relationship between the first printing fluid reference point and the second printing fluid reference point so that an first printing fluid printing process and a second printing fluid printing process can be aligned during operation of a printing system.

A printing system adapted to receive a print target, the printing system comprising:

• an first printing fluid printing system;
• a second printing fluid printing system;
• and
• a controller including a processor and a non-transitory machine-readable storage medium,
• wherein the storage medium comprises instructions, which, when executed by the processor, control the processor to:
• print a calibration target on a print target, comprising:
• printing an first printing fluid figure on the print target;
• and
• printing a second printing fluid figure on the print target, wherein the second printing fluid figure defines a geometric figure negatively outlined in the second printing fluid figure;
• obtain image data relating to a first region of interest of an image of the calibration target and image data relating to a second region of interest of an image of the calibration target;
• process the image data relating to the first region of interest to locate the borders of the first printing fluid figure captured in the calibration target image;
• determine the location of an first printing fluid reference point based upon the detected borders of the first printing fluid figure;
• process the image data relating to the second region of interest to locate geometric features of the geometric figure defined by the second printing fluid figure;
• determine the location of a second printing fluid reference point on the print target by matching the located geometric features with reference geometric features from a reference geometric figure;
• and
• determine a geometric relationship between the first printing fluid reference point and the second printing fluid reference point so that an first printing fluid printing process and a second printing fluid printing process can be aligned during operation of a printing system;
• and wherein the controller is configured, in use, to:
• retrieve the instructions from the storage medium;
• and
• cause the instructions to be executed by the processor so first printing fluid printed by the first printing fluid printing system and second printing fluid printed by the second printing fluid printing system are aligned during operation of the printing system.