How to perform OCR on different font sizes

This article relates to Scan2CAD v9.

Hopefully all of your drawings which hold text, all contain same font size.

Of-course this isn’t always the case. So here’s some handy tips to deal with images which hold fonts of different sizes.

1. Is the text very small?

Scan2CAD is unlikely to recognize text that is smaller than five pixels in size, or even text that is slightly larger than this where letters are complex. This is because where text is very small there are simply not enough pixels in each letter to adequately represent the letter’s shape so that it can be recognized.

 2. Have you set the correct Character Size Limits?

It is important to set the Character Size Limits correctly. Scan2CAD will only recognize an item as text if it is smaller than the Maximum Character Size Limit but larger than the Minimum Character Size Limit.

Character Size Limits can be set from the OCR Settings dialog.

OCR Menu > Settings…

Do not set the Maximum Character Size Limit to a very large value in the hope of recognizing all the text on the image. If you do this, Scan2CAD is likely to miss text on the image even though it is smaller than the Maximum Limit. You are also more likely to experience non-text drawing elements being incorrectly converted to text.

Set the Maximum Character Size Limit to a value slightly larger than the height of most of the text on the image.

Do this using OCR Menu > Char Size or OCR Menu > Settings…

3. Major Font Size Variations

If there are major variations in text size on the image, you may want to convert areas of different sized text separately using different Maximum Character Size Limits. You can do this by selecting an area of text of one size, converting it, selecting an area of text of another size, converting it, etc.