Reducing the dynamic range of image data

A computer system for determining low dynamic range image data from high dynamic range image data, the system comprising:

• an input port to receive or access the high dynamic range image data;
• and
• a processor to determine the low dynamic range image data based on the high dynamic range image data by optimising a degree to which the low dynamic range image data satisfies a local contrast constraint and a global consistency constraint, wherein
• the local contrast constraint is based on a local contrast in a perception space;
• the global consistency constraint is based on a relationship between points in the high dynamic range image data.

A vision enhancement apparatus for enhancing vision for a vision impaired user of high dynamic range image data, the apparatus comprising:

• an input port to receive or access the high dynamic range image data;
• a processor to determine the low dynamic range image data based on the high dynamic range image data by optimising a degree to which the low dynamic range image data satisfies a local contrast constraint and a global consistency constraint, wherein
• the local contrast constraint is based on a local contrast in a perception space;
• the global consistency constraint is based on a relationship between points in the high dynamic range image data;
• and
• a display to display or to cause the display of the low dynamic range image data to the vision impaired user.