Calibrating print apparatus

A print apparatus, comprising:

• a print engine comprising a print head, the print engine to:
• print, from nozzles of a first die of the print head onto print media, a first image in a first color and a second image in a second color, the images being based on a pattern comprising a plurality of patches of different densities;
• and
• print, from nozzles of a second die of the print head onto the print media, a first image in the first color and a second image in the second color, the images being based on the pattern, wherein the first color printed by the first die on the first image is located in a same corresponding position of the pattern as the first color printed by the second die, and wherein the second color printed by the first die on the first image is located in a same corresponding position of the pattern as the second color printed by the second die;
• and
• a processing resource to:
• receive scanned image data generated by scanning the first and second images in the first color using a first scanning module and by scanning the first and second images in the second color using a second scanning module;
• analyze the scanned image data to identify any differences between print agent densities of the first color printed by the first die on the first image located in the same corresponding position of the pattern as the first color printed by the second die, or of the second color printed by the first die on the first image located in the same corresponding position of the pattern as the second color printed by the second die;
• and
• perform a calibration based on the analysis.

A non-transitory machine-readable medium comprising instructions which, when executed by a processor, cause the processor to:

• operate a print apparatus to deliver print agent, from each of a plurality of dies of a print head onto a print agent receiving surface, to form from each die a first image in a first color and a second image in a second color, wherein each image is based on a calibration pattern comprising a plurality of regions having a plurality of different print density levels, wherein a first die of the plurality of dies prints the first image in the first color according to the calibration pattern and a second die of the plurality of dies prints the second image in the second color according to the calibration pattern, wherein the first image in the first color printed by the first die is located in a same corresponding position of the calibration pattern as the second image in the second color printed by the second die;
• operate:
• a first scanning module to scan the first and second images formed on the print agent receiving surface in the first color;
• and
• a second scanning module to scan the first and second images formed on the print agent receiving surface in the second color, to generate scanned image data;
• analyze the scanned image data to identify a discrepancy between the print density levels of the first color printed by the first die in the same position of the calibration pattern in the first image and the second color printed by the second die in the same position of the calibration pattern in the second image;
• and
• perform a calibration operation based on the analysis.