I require free scientific image measurement software to measure the distance and area of an SEM image. I have been using Gwyddion but it is creating problem with Windows 7
Please specify what type of irregular line ? All the above mentions/ suggested software are going to help you for measuring straight, curve lines, area etc.
I will measure marginal adaptation of fissure sealant on sem images. I downloaded ImageJ, Photoshop but only I could measure straight lines. For irregular or curved lines which of the software should I use?
Gatan Digital Micrograph has a free license available for download in his website. It's a good free offline version, and there are plenty of scripts available. There is a link on our website that let you go straight to the right link in Gatan website. Look for "links" at left side menu on our website. In addition, google "DM scripts" to found out more. This software is broadly used and user friendly.
It is for geometry teaching purposes, yet it is a very nice software: free for non-commercial purposes and downloadabe for off-line use. You can use an image for background and work on an above layer.
Everyone is going to tell you ImageJ. It's free, comes with a host of tools, has an excellent online support presence, is customizable. This is your best bet. Link is in many of the other responses.
You should first define the scale from Image tab following Image > Analysis > Set Measurement Scale > Custom. Then you can measure a distance with the ruler option, and for area, after defining the region with lasso or other tools, you should follow Image > Analysis > Record Measurements.