Is there a code to replace image toolbox function 'ind2gray'?

I am using the 'ind2gray' function of the image processing toolbox and our licence is due to expire. Considering this is the only function of the tool box used I am wondering if there is a code to replace it?

Answer 1

[Walter Roberson]

Use the formula shown in http://www.mathworks.com/matlabcentral/answers/159282-convert-from-rgb-to-grayscale-without-rgb2gray to convert your map into grayscale. Then use the indices to index that grayscale data. If the indices are floating point then use the indices directly; if the indices are uint8() or uint16() then double() and add 1 and index with that.