Thank you for a good idea.
The image which I was trying to import which shows the problem which I was trying to solve was obtained as follows.
If one goes to http://special-1.bl.uk/treasures/festiv ... kList.aspx
and then clicks forward to page 4 of 11, there is a link to images from a book published in London in 1641.
http://special-1.bl.uk/treasures/festiv ... rFest=0247
Page 002 has an illustration at the top of the page. I enlarged it using the + button which is on the screen.
Using a screen display of 800 pixels wide by 600 pixels high (which is the screen resolution at which I normally use the computer, no special reason related to this image), I used the Print Screen button on the keyboard and then pasted the image into Microsoft Paint and saved as a 24-bit bmp.
I trimmed the image so that there was only the illustration and some paper around it. The result was 770 pixels wide by 270 pixels high.
The problem that I was having was that the outside right-side quarter needs a different threshold value to the outside left-side quarter.
Your suggestion provides an opportunity to have another try.
I find the design of the illustration interesting. The two halves have the same general shape, yet the details are different. For example, the flowers in each of the upper outside corners are different, though there is a flower in each corner.
19 June 2008